Molecular evaluation of <Emphasis Type="Italic">PIK3CA</Emphasis> gene mutation in breast cancer: determination of frequency,distribution pattern and its association with clinicopathological findings in Indian patients

Somatic mutations in the PIK3CA gene are common in breast cancer and represent a clinically useful marker for prognosis and therapeutic target. Activating mutations in the PI3K p110 catalytic subunit (PIK3CA) have been identified in 18–40 % of breast carcinomas. In this study, we evaluated PIK3CA mutation in 185 Indian breast cancer patients by direct DNA sequencing. PIK3CA mutations were observed in 23.2 % (43/185) of breast tumor samples. PIK3CA mutations were more frequent exon 30 (76.8 %) than in exon 9 (23.2 %). Mutations were mostly clustered within two hotspot region between nucleotides 1624 and 1636 or between 3129 and 3140. Sequencing analysis revealed four different missense mutations at codon 542 and 545 (E542K, E545K, E545A and E545G) in the helical domain and two different amino acid substitutions at codon 1047 (H1047R and H1047L) in the kinase domain. None of the cases harbored concomitant mutations at multiple codons. PIK3CA mutations were more frequent in older patients, smaller size tumors, ductal carcinomas, grade II tumors, lymph node-positive tumors and non-DCIS tumors; however, none of the differences were significant. In addition, PIK3CA mutations were common in ER+, PR+ and HER2+ cases (30 %), and a comparatively low frequency were noted in triple-negative tumors (13.6 %). In conclusion, to our knowledge, this is the largest study to evaluate the PIK3CA mutation in Indian breast cancer patients. The frequency and distribution pattern of PIK3CA mutations is similar to global reports. Furthermore, identification of molecular markers has unique strengths and can provide insights into the pathogenic process of breast carcinomas.     

Prognostic role of tumor PIK3CA mutation in colorectal cancer: a systematic review and meta-analysis

BackgroundSomatic mutations in the phosphatidylinositol-4,5-bisphosphate 3-kinase/AKT pathway play a vital role in carcinogenesis. Approximately 15%–20% of colorectal cancers (CRCs) harbor activating mutations in PIK3CA, making it one of the most frequently mutated genes in CRC. We thus carried out a systematic review and meta-analysis investigating the prognostic significance of PIK3CA mutations in CRC.Materials and methodsElectronic databases were searched from inception through May 2015. We extracted the study characteristics and prognostic data of each eligible study. The hazard ratio (HR) and 95% confidence interval (CI) were derived and pooled using the random-effects Mantel–Haenszel model.ResultsTwenty-eight studies enrolling 12 747 patients were eligible for inclusion. Data on overall survival (OS) and progression-free survival (PFS) were available from 19 and 10 studies, respectively. Comparing PIK3CA-mutated CRC patients with PIK3CA-wild-type CRC patients, the summary HRs for OS and PFS were 0.96 (95% CI 0.83–1.12) and 1.20 (95% CI 0.98–1.46), respectively. The trim-and-fill, Copas model and subgroup analyses stratified by the study characteristics confirmed the robustness of the results. Five studies reported the CRC prognosis for PIK3CA mutations in exons 9 and 20 separately; neither exon 9 mutation nor exon 20 mutation in PIK3CA was significantly associated with patient survival.ConclusionsOur findings suggest that PIK3CA mutation has the neutral prognostic effects on CRC OS and PFS. Evidence was accumulating for the establishment of CRC survival between PIK3CA mutations and patient-specific clinical or molecular profiles.     

Contralateral prophylactic mastectomy and its association with reduced mortality: evidence for selection bias

Mutations in the PIK3CA gene are common in breast cancer and represent a clinically useful therapeutic target. Several larger, population-based studies have shown a positive prognostic significance associated with these mutations. This study aims to further identify characteristics of patients harboring PIK3CA mutations while evaluating the clinical impact of genomic testing for these mutations. Tumors from 312 patients at Vanderbilt-Ingram Cancer Center were analyzed for PIK3CA mutations using a multiplex screening assay (SNaPshot). Mutation rates, receptor status, histopathologic characteristics, and time to recurrence were assessed. The number of patients participating in clinical trials, specifically trials relating to the PIK3CA mutation, was examined. Statistically significant differences between wild-type and mutated tumors were determined using the Wilcoxon, Pearson, and Fischer exact tests. The PIK3CA mutation was found in 25 % of tumors tested. Patients with PIK3CA mutations were significantly more likely to express hormone receptors, be of lower combined histological grade, and have a reduced time to recurrence. Patients found to have a PIK3CA mutation were significantly more likely to enter a PIK3CA-specific clinical trial. In addition to confirming previously established positive prognostic characteristics of tumors harboring PIK3CA mutations, this study demonstrates the feasibility and utility of mutation profiling in a clinical setting. PIK3CA mutation testing impacted treatment and resulted in more patients entering mutation-specific clinical trials.     

PIK3CA exon 20 mutations as a potential biomarker for resistance to anti-EGFR monoclonal antibodies in KRAS wild-type metastatic colorectal cancer: a systematic review and meta-analysis

BackgroundWe conducted a systematic review and meta-analysis to dissect the association between PIK3CA mutations and resistance to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs) according to PIK3CA exon of mutations in metastatic colorectal cancer (mCRC).MethodsWe systematically identified studies exploring the association between PIK3CA mutations and clinical outcomes of mCRC patients treated with anti-EGFR MoAbs. The primary clinical outcomes included objective response rate (ORR), progression-free survival (PFS), and overall survival (OS). The pooled relative risk (RR) or hazard ratio (HR) was estimated by using fixed effect model or random effect model according to heterogeneity between studies.ResultsThirteen studies were considered eligible, with 576 mCRC patients included. In KRAS wild-type mCRC patients, we observed a lower ORR in patients with PIK3CA exon 20 mutations [3 studies, 377 patients; ORR = 0% versus 37%; RR = 0.25; 95% confidence interval (CI) 0.05–1.19; P = 0.082], although the result was not statistically significant because of the small sample size. Only one study provided survival data according to the PIK3CA exon of the mutations, in which PIK3CA exon 20 mutations were statistically significantly associated with shorter PFS (HR = 2.52; 95% CI 1.33–4.78; P = 0.013) and OS (HR = 3.29; 95% CI 1.60–6.74; P = 0.006) in KRAS wild-type mCRC patients treated with anti-EGFR MoAbs. The predictive power of exon 20 mutation is greater than exon 9 mutations and all exons mutations in terms of ORR, PFS, and OS.ConclusionThese analyses suggest that PIK3CA exon 20 mutations may be a potential biomarker for resistance to anti-EGFR MoAbs in KRAS wild-type mCRC.     

PIK3CA kinase domain mutation identifies a subgroup of stage III colon cancer patients with poor prognosis

Background

PIK3CA mutations in the helical domain (in exon 9) and in the kinase domain (exon 20) cause tumor formation by different means. We aimed to determine the effects of each of these mutations on survival of colon carcinoma patients.

Methods

A large cohort of 685 colon carcinoma patients was tested for PIK3CA mutations in exons 9 and 20 by single nucleotide primer extension (N?=?428) or by real time PCR (N?=?257).

Results

PIK3CA mutation rate was 13%. 66 of 83 (79.5%) were in exon 9 and 17 of 83 (20.5%) in exon 20. In survival analysis, PIK3CA mutations in exon 9 and 20 had different effects on patient outcome. The PIK3CA exon 20 mutation conferred a poorer disease free survival compared to patients with wild type alleles and exon 9 mutations (Log rank p?=?0.04 and p?=?0.03 respectively) and cancer specific survival (Log rank p?=?0.03 and p?=?0.056 respectively) in stage III patients. In stage I and II this negative effect on outcome was not seen.

Conclusions

PIK3CA mutation in exon 20 is a negative prognostic factor in stage III colon cancer patients. Moreover, this negative effect is not present in stage I and II patients.     

PIK3CA mutations in non-small cell lung cancer (NSCLC): Genetic heterogeneity,prognostic impact and incidence of prior malignancies

Background: Somatic mutations of the PIK3CA gene have been described in non-small cell lung cancer (NSCLC), but limited data is available on their biological relevance. This study was performed to characterize PIK3CA-mutated NSCLC clinically and genetically.Patients and methods: Tumor tissue collected consecutively from 1144 NSCLC patients within a molecular screening network between March 2010 and March 2012 was analyzed for PIK3CA mutations using dideoxy-sequencing and next-generation sequencing (NGS). Clinical, pathological, and genetic characteristics of PIK3CA-mutated patients are described and compared with a control group of PIK3CA-wildtype patients.Results: Among the total cohort of 1144 patients we identified 42 (3.7%) patients with PIK3CA mutations in exon 9 and exon 20. These mutations were found with a higher frequency in sqamous cell carcinoma (8.9%) compared to adenocarcinoma (2.9%, p<0.001). The most common PIK3CA mutation was exon 9 E545K. The majority of patients (57.1%) had additional oncogenic driver aberrations. With the exception of EGFR-mutated patients, non of the genetically defined subgroups in this cohort had a significantly better median overall survival. Further, PIK3CA-mutated patients had a significantly higher incidence of malignancy prior to lung cancer (p<0.001).Conclusion: PIK3CA-mutated NSCLC represents a clinically and genetically heterogeneous subgroup in adenocarcinomas as well as in squamous cell carcinomas with a higher prevalence of these mutations in sqamous cell carcinoma. PIK3CA mutations have no negative impact on survival after surgery or systemic therapy. However, PIK3CA mutated lung cancer frequently develops in patients with prior malignancies.     

PIK3CA mutations,phosphatase and tensin homolog,human epidermal growth factor receptor 2, and insulin-like growth factor 1 receptor and adjuvant tamoxifen resistance in postmenopausal breast cancer patients

Introduction

Inhibitors of the phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway can overcome endocrine resistance in estrogen receptor (ER) α-positive breast cancer, but companion diagnostics indicating PI3K/AKT/mTOR activation and consequently endocrine resistance are lacking. PIK3CA mutations frequently occur in ERα-positive breast cancer and result in PI3K/AKT/mTOR activation in vitro. Nevertheless, the prognostic and treatment-predictive value of these mutations in ERα-positive breast cancer is contradictive. We tested the clinical validity of PIK3CA mutations and other canonic pathway drivers to predict intrinsic resistance to adjuvant tamoxifen. In addition, we tested the association between these drivers and downstream activated proteins.

Methods

Primary tumors from 563 ERα-positive postmenopausal patients, randomized between adjuvant tamoxifen (1 to 3 years) versus observation were recollected. PIK3CA hotspot mutations in exon 9 and exon 20 were assessed with Sequenom Mass Spectometry. Immunohistochemistry was performed for human epidermal growth factor receptor 2 (HER2), phosphatase and tensin homolog (PTEN), and insulin-like growth factor 1 receptor (IGF-1R). We tested the association between these molecular alterations and downstream activated proteins (like phospho-protein kinase B (p-AKT), phospho-mammalian target of rapamycin (p-mTOR), p-ERK1/2, and p-p70S6K). Recurrence-free interval improvement with tamoxifen versus control was assessed according to the presence or absence of canonic pathway drivers, by using Cox proportional hazard models, including a test for interaction.

Results

PIK3CA mutations (both exon 9 and exon 20) were associated with low tumor grade. An enrichment of PIK3CA exon 20 mutations was observed in progesterone receptor- positive tumors. PIK3CA exon 20 mutations were not associated with downstream-activated proteins. No significant interaction between PIK3CA mutations or any of the other canonic pathway drivers and tamoxifen-treatment benefit was found.

Conclusion

PIK3CA mutations do not have clinical validity to predict intrinsic resistance to adjuvant tamoxifen and may therefore be unsuitable as companion diagnostic for PI3K/AKT/mTOR inhibitors in ERα- positive, postmenopausal, early breast cancer patients.     

Phosphatidyl-inositol-3-kinase alpha catalytic subunit mutation and response to neoadjuvant endocrine therapy for estrogen receptor positive breast cancer

Mutations in the alpha catalytic subunit of phosphoinositol-3-kinase (PIK3CA) occur in ~30% of ER positive breast cancers. We therefore sought to determine the impact of PIK3CA mutation on response to neoadjuvant endocrine therapy. Exons 9 (helical domain) and 20 (kinase domain—KD) mutations in PIK3CA were determined samples from four neoadjuvant endocrine therapy trials. Interactions with clinical, pathological, and biomarker response parameters were examined. A weak negative interaction between PIK3CA mutation status and clinical response to neoadjuvant endocrine treatment was detected (N = 235 P ≤ 0.05), but not with treatment-induced changes in Ki67-based proliferation index (N = 418). Despite these findings, PIK3CA KD mutation was a favorable prognostic factor for relapse-free survival (RFS log-rank P = 0.02) in the P024 trial (N = 153). The favorable prognostic effect was maintained in a multivariable analysis (N = 125) that included the preoperative endocrine prognostic index, an approach to predicting RFS based on postneoadjuvant endocrine therapy pathological stage, ER, and Ki67 levels (HR for no PIK3CA KD mutation, 14, CI 1.9–105 P = 0.01). PIK3CA mutation status did not strongly interact with neoadjuvant endocrine therapy responsiveness in estrogen receptor-positive breast cancer. Nonetheless, as with other recent studies, a favorable interaction between PIK3CA KD mutation and prognosis was detected. The mechanism for the favorable prognostic impact of PIK3CA mutation status therefore remains unexplained.     

PIK3CA mutations, PTEN, and pHER2 expression and impact on outcome in HER2-positive early-stage breast cancer patients treated with adjuvant chemotherapy and trastuzumab

BackgroundThis study was conducted to determine the frequency of PIK3CA mutations and human epidermal growth factor receptor-2 (HER2) phosphorylation status (pHER2-Tyr^1221/1222) and if PIK3CA, phosphatase and tensin homolog (PTEN), or pHER2 has an impact on outcome in HER2-positive early-stage breast cancer patients treated with adjuvant chemotherapy and trastuzumab.Patients and methodsTwo hundred and forty HER2-positive early-stage breast cancer patients receiving adjuvant treatment (cyclophosphamide 600 mg/m², epirubicin 60 mg/m², and fluorouracil 600 mg/m²) before administration of 1 year trastuzumab were assessable. PTEN and pHER2 expression were assessed by immunohistochemistry. PIK3CA mutations (exons 9 and 20) were determined by pyrosequencing.ResultsFive-year overall survival (OS) and invasive disease-free survival were 87.8% and 81.0%, respectively. Twenty-six percent of patients had a PIK3CA mutation, 24% were PTEN low, 45% pHER2 high, and 47% patients had increased PI3K pathway activation (PTEN low and/or PIK3CA mutation). No significant correlations were observed between the clinicopathological variables and PIK3CA, PTEN, and pHER2 status. In both univariate and multivariate analyses, patients with PIK3CA mutations or high PI3K pathway activity had a significant worse OS [multivariate: hazard ratio (HR) 2.14, 95% confidence interval (CI) 1.01–4.51, P = 0.046; and HR 2.35, 95% CI 1.10–5.04, P = 0.03].ConclusionPatients with PIK3CA mutations or increased PI3K pathway activity had a significantly poorer survival despite adequate treatment with adjuvant chemotherapy and trastuzumab.     

PIK3CA mutation in Chinese patients with lung squamous cell carcinoma

Objective

To investigate PIK3CA mutation in Chinese patients with lung squamous cell carcinoma (LSCC) and explore their relationship with clinicopathological profiles.

Methods

Tumor samples from 123 cases of LSCC were included in this study. PIK3CA mutations in exon 9 and 20 were screened by pyrosequencing and confirmed by clone sequencing or amplification refractory mutation system (ARMS). Denaturing performance liquid chromatography (DHPLC) was employed for evaluation of EGFR mutation in exon 19, 21 and KRAS mutation.

Results

PIK3CA mutations were found in 3 (2.4%) patients. The mutation type included E545K, E452Q and H1047R. Of these three patients, one coupled with EGFR mutation, and the other two coupled with PIK3CA amplification. All the three patients shared the same clinicopathologic characteristics: male, less than 60 years old, had smoke history, stage III and carried wild-type KRAS.

Conclusions

The frequency of PIK3CA mutation is low in Chinese patients with LSCC. The mutational status of PIK3CA is not mutually exclusive to EGFR mutation.Key Words: Lung squamous cell carcinoma (LSCC), PIK3CA mutation, EGFR mutation, KRAS mutation     

Prediction for response duration to epidermal growth factor receptor-tyrosine kinase inhibitors in EGFR mutated never smoker lung adenocarcinoma

Objectives

Among non-small cell lung cancer (NSCLC) patients harboring activating epidermal growth factor receptor (EGFR) mutations, ∼20–30% exhibit de novo resistance to EGFR-tyrosine kinase inhibitor (TKI). The aim of this study was to examine whether mutations in the EGFR-downstream genes may be associated with de novo resistance to EGFR-TKIs in EGFR mutation-positive patients.

Materials and methods

Sixty-eight never-smoker adenocarcinoma patients with an activating EGFR mutation were included in the mutational analysis and 55 patients treated with EGFR-TKIs were analyzed for the treatment outcomes to EGFR-TKIs. We concurrently analyzed mutations in PIK3CA, PTEN, AKT and STK11, which are all EGFR-downstream genes. Mutations in PIK3CA, PTEN, AKT, and STK11 were analyzed by polymerase chain reaction-based sequencing.

Results

PIK3CA mutations were detected in 4.4% (3/68) of patients, PTEN mutations in 16.1% (11/68), AKT mutations in 5.9% (4/68), and STK11 mutations in 13.2% (9/68). One patient with an activating exon 21 L858R mutation concomitantly had an exon 20 T790M mutation in EGFR. The proportion of patients who had mutations in EGFR-downstream genes was 32.4% (22/68). When we analyzed the treatment outcome of 55 patients treated with EGFR-TKI, the presence of mutations in EGFR-downstream genes correlated with a poor overall response rate to EGFR-TKIs (63.6 vs.14.5% in patients with mutation in EGFR-downstream gene, P < 0.0001), shorter median progression-free survival (12.0 vs. 3.0 months, P = 0.060), and shorter median overall survival (18.9 vs. 25.0 months, P = 0.048).

Conclusion

Mutations in the EGFR-downstream genes may confer resistance to EGFR-TKIs and result in poor treatment outcomes in never-smoker adenocarcinoma patients with activating EGFR mutations.     

Low PTEN levels and <Emphasis Type="Italic">PIK3CA</Emphasis> mutations predict resistance to neoadjuvant lapatinib and trastuzumab without chemotherapy in patients with HER2 over-expressing breast cancer

Purpose

Aberrant activation of the PI3K pathway has been implicated in resistance to HER2-targeted therapy, but results of clinical trials are confounded by the co-administration of chemotherapy. We investigated the effect of perturbations of this pathway in breast cancers from patients treated with neoadjuvant anti-HER2-targeted therapy without chemotherapy.

Patients and methods

Baseline tumor samples from patients with HER2-positive breast cancer enrolled in TBCRC006 (NCT00548184), a 12-week neoadjuvant clinical trial with lapatinib plus trastuzumab [plus endocrine therapy for estrogen receptor (ER)-positive tumors], were assessed for PTEN status by immunohistochemistry and PIK3CA mutations by sequencing. Results were correlated with pathologic complete response (pCR).

Results

Of 64 evaluable patients, PTEN immunohistochemistry and PIK3CA mutation analysis were performed for 59 and 46 patients, respectively. PTEN status (dichotomized by H-score median) was correlated with pCR (32% in high PTEN vs. 9% in low PTEN, p = 0.04). PIK3CA mutations were identified in 14/46 tumors at baseline (30%) and did not correlate with ER or PTEN status. One patient whose tumor harbored a PIK3CA mutation achieved pCR (p = 0.14). When considered together (43 cases), 1/25 cases (4%) with a PIK3CA mutation and/or low PTEN expression levels had a pCR compared to 7/18 cases (39%) with wild-type PI3KCA and high PTEN expression levels (p = 0.006).

Conclusion

PI3K pathway activation is associated with resistance to lapatinib and trastuzumab in breast cancers, without chemotherapy. Further studies are warranted to investigate how to use these biomarkers to identify upfront patients who may respond to anti-HER2 alone, without chemotherapy.

     

Clinical usefulness of KRAS, BRAF, and PIK3CA mutations as predictive markers of cetuximab efficacy in irinotecan- and oxaliplatin-refractory Japanese patients with metastatic colorectal cancer

Background

Anti-epidermal growth factor receptor (EGFR) antibodies, cetuximab, and panitumumab are established as a new treatment option for metastatic colorectal cancer (mCRC). Among activating mutations downstream of EGFR, the KRAS mutation, which is present in 30–45 % of CRC patients, has shown to be a predictive biomarker of resistance to anti-EGFR antibody therapy based on Caucasian studies.

Methods

Forty-three chemotherapy-refractory Japanese patients with mCRC were treated with cetuximab monotherapy or cetuximab plus irinotecan. KRAS, BRAF, and PIK3CA mutational status of tumors was assessed. The association between mutational status and treatment outcome was evaluated.

Results

Of 43 tumors, KRAS, BRAF, and PIK3CA mutations were identified in 12 (27.9 %), 2 (4.7 %), and 2 (4.7 %) tumors, respectively. The wild-type KRAS subgroup showed better clinical outcomes than the mutant KRAS subgroup in terms of response rate (RR) (31.3 % vs. 0 %, P = 0.034) and progression-free survival (PFS) (5.1 vs. 3.0 months, P = 0.017). No responder to treatment was shown in 16 (37.2 %) patients with tumors harboring mutations in any one of the three genes (KRAS, BRAF, and PIK3CA). The wild-type subgroup without any mutations in KRAS, BRAF, and PIK3CA had a better RR (37.0 %) and PFS (6.4 months) than did the wild-type KRAS subgroup.

Conclusion

Our data indicated that KRAS status is predictive of cetuximab response in the Japanese population. The additional analysis of BRAF and PIK3CA genes in wild-type KRAS patients could improve selection of patients who are most likely to benefit from anti-EGFR antibody therapy.     

CYP2D6 polymorphisms influence tamoxifen treatment outcomes in breast cancer patients: a meta-analysis

Purpose

To evaluate whether breast cancer (BC) patients with CYP2D6 gene variation have different clinical tamoxifen (TAM) treatment outcomes to those with normal function of CYP2D6.

Methods

Systematic searches of the PubMed up to February 21, 2013, were retrieved. The study end points were disease-free survival (DFS) and overall survival (OS). Fixed or random-effects meta-analytical models were used to calculate summary hazard ratio (HR) and corresponding 95 % confidence intervals (CIs). Meta-regression, Galbraith plots, subgroup analysis, and sensitivity analysis were also performed.

Results

A total of 11,701 BC patients from 20 trials were included. Compared with reduced CYP2D6 function, normal function was associated with a trend toward improved DFS (HR = 1.37, 95 % CI 1.12–1.69, P = 0.002) and OS (HR = 1.25, 95 % CI 1.03–1.50, P = 0.021). We found significant heterogeneity between studies. When the analysis was stratified into subgroups, significantly worse DFS was found in the groups of intermediate metabolizer versus extensive metabolizer (HR = 1.65, 95 % CI 1.04–2.64, P = 0.035), Asian population (HR = 3.29, 95 % CI 1.64–6.63, P = 0.001), 5 years TAM treatment duration (HR = 1.59; 95 % CI 1.14–2.22, P = 0.006), concomitant chemotherapy (HR = 1.35, 95 % CI 1.04–1.76, P = 0.025), and TAM alone (HR = 1.44, 95 % CI 1.44–2.06, P = 0.045). With respect to OS, no significant association was demonstrated in stratified analyses.

Conclusions

We concluded that CYP2D6 polymorphisms may influence tamoxifen treatment outcomes of DFS in BC patients.     

Mutations in EGFR, BRAF and RAS are rare in triple-negative and basal-like breast cancers from Caucasian women

Basal-like and triple-negative breast cancers usually display a high level of genomic instability and often carry TP53 mutations. Mutations in EGFR have been reported in about 10 % triple-negative tumours from Chinese women, and there is some evidence that triple-negative and basal-like tumours might carry additional mutations against which targeted therapies are available. We, therefore, sought to determine the frequency of 238 targetable mutations in 19 oncogenes (including EGFR) in a panel of basal-like and triple-negative breast cancers from Caucasian women. We used the OncoCarta panel to screen for 238 mutations across 19 common oncogenes in 107 basal-like and triple-negative breast cancers from Caucasian women. Mutations were then verified using Sanger sequencing or primer extension by iPLEX. We identified and validated 10 mutations across five genes. Most of the mutations were observed in the PIK3CA gene (18/107, 16.8 %), while mutations in KRAS, NRAS, MET and AKT1 were present in only one tumour each (1/107, 0.9 %). Among the missense substitutions in PIK3CA the point mutation resulting in the amino acid change H1047R was the most frequent (8/18, 44 %). All mutations were mutually exclusive, apart from one basal-like breast tumour which harboured mutations in both MET (p.T992I) and PIK3CA (p.H1047R). We did not identify any mutations in the EGFR gene. In conclusion, we found that with the exception of mutations in PIK3CA, these actionable oncogenic mutations on the Oncocarta panel are rare in basal-like and triple-negative breast cancers from Caucasian women. Custom panels, designed to detect mutations identified by exome sequencing of basal-like and triple-negative breast cancers, are, therefore, needed to identify women who might be eligible for targeted treatment.     

Prognostic and predictive value of common mutations for treatment response and survival in patients with metastatic colorectal cancer

Background:

We address the prognostic and predictive value of KRAS, PIK3CA and BRAF mutations for clinical outcomes in response to active agents in the treatment of metastatic colorectal cancer (mCRC).

Methods:

We determined KRAS, BRAF and PIK3CA mutations in tumours from 168 patients treated for mCRC at two institutions. All patients received 5-FU-based first-line chemotherapy and treatment outcome was analysed retrospectively.

Results:

KRAS, BRAF and PIK3CA mutations were present in 62 (37%), 13 (8%) and 26 (15%) cases, respectively. Multivariate analysis uncovered BRAF mutation as an independent prognostic factor for decreased survival (hazard ratio (HR) 4.0, 95% confidence interval (CI) 2.1–7.6). In addition, patients with BRAF-mutant tumours had significantly lower progression-free survival (PFS: HR 4.0, 95% CI 2.2–7.4) than those whose tumors that carried wild-type BRAF. Among 92 patients treated using chemotherapy and cetuximab as salvage therapy, KRAS mutation was associated with lack of response (P=0.002) and shorter PFS (P=0.09). BRAF (P=0.0005) and PIK3CA (P=0.01) mutations also predicted reduced PFS in response to cetuximab salvage therapy.

Conclusions:

These results underscore the potential of mutational profiling to identify CRCs with different natural histories or treatment responses. The adverse significance of BRAF mutation should inform patient selection and stratification in clinical trials.     

Low Frequency of <Emphasis Type="Italic">PIK3CA</Emphasis> Gene Mutations in Hepatocellular Carcinoma in Chinese Population

PI3K/AKT constitutes an important pathway regulating the signaling of multiple biological processes and plays a critical role in carcinogenesis. PIK3CA gene missense mutations have been reported in many human cancer types. The mutation of it in hepatocellular carcinoma cases varies with different races and regions. In this study, we investigated PIK3CA mutation in Chinese hepatocellular carcinoma patients. A total 90 Chinese patients of hepatocellular carcinoma were recruited in this study. Exons 9 and 20 hotspots mutations of PIK3CA gene were detected by PCR-based DNA sequencing. Two point mutations (E542K and D549H) in exon 9 were found in only one patient (1/90; 1.11%), no mutation was found in exon 20 in any cases. 57 patients are associated with HBV infection (57/90; 63.3%), and 8 patients with HCV infection (8/90; 8.9%). The frequency of the PIK3CA mutations in hepatocellular carcinoma seems to be lower in Chinese hepatocellular carcinoma patients. These findings suggest that PI3K mutations may not play a major role in hepatic carcinogenesis in Chinese. HBV infection has close relationship with HCC in Chinese.     

PIK3CA Mutations in Advanced Cancers: Characteristics and Outcomes

PIK3CA mutations are frequently diagnosed in diverse cancers and may predict response to PI3K/AKT/mTOR inhibitors. It remains unclear whether they are associated with other characteristics. We analyzed characteristics and outcome of 90 consecutive patients with diverse advanced tumors and PIK3CA mutations and 180 wild-type PIK3CA controls matched by tumor type, gender, and age referred to the Clinical Center for Targeted Therapy. PIK3CA and MAPK mutations (KRAS, NRAS, and BRAF) were analyzed using polymerase chain reaction-based DNA sequencing. The most frequent PIK3CA mutations were E545K (31/90, 34%), E542K (16/90, 18%) in exon 9, and H1047R (20/90, 22%) in exon 20. PIK3CA mutations compared to wild-type PIK3CA were associated with simultaneous KRAS (p=0.047) and MAPK mutations (p=0.03), but only MAPK mutations were confirmed as having an independent association in multivariate analysis. Rates of lung, bone, liver and brain metastases were similar in PIK3CA-mutant and wild-type patients. Patients with PIK3CA mutations treated on trials with PI3K/AKT/mTOR inhibitors had a higher partial/complete response (PR/CR) rate than wild-type PIK3CA patients treated with their best phase I therapy (10/56, 18% vs. 12/152, 8%; p=0.045), but not a prolonged progression-free survival. Patients with H1047R PIK3CA mutations had a higher PR/CR rate with PI3K/AKT/mTOR inhibitors compared to wild-type PIK3CA patients treated with their best phase I therapy (6/16, 38% vs. 12/152, 8%; p=0.003). In conclusion, PIK3CA mutations in diverse cancers were not associated with clinical characteristics, but were correlated with MAPK mutations. PIK3CA mutations, especially, H1047R, were associated with attaining a PR/CR to PI3K/AKT/mTOR pathway inhibitors.     

APOBEC3B is an enzymatic source of molecular alterations in esophageal squamous cell carcinoma

APOBEC3B belongs to the cytidine deaminase apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC3) family of enzymes and induces C to T transitions of target DNA by cytidine deamination. Recently, several mutations in various cancers have been linked to APOBEC3B, suggesting a crucial role for this protein in carcinogenesis and cancer development. However, the significance of APOBEC3B in esophageal squamous cell carcinoma (ESCC) remains uncertain. In addition, the APOBEC3B immunoreactivity in cancer tissues is uncertain. Recently, we have demonstrated that PIK3CA mutation and the methylation level of long interspersed nucleotide element 1 (LINE-1) (a surrogate marker of global DNA methylation level) are prognostic markers and have crucial role on malignancy in ESCC patients. This study aims to clarify the impact of APOBEC3B on the clinical, pathological, and molecular features of ESCC. We evaluated APOBEC3B expression in ESCC and investigated the relationships among the immunoreactivity of APOBEC3B, clinical and pathological features, and the molecular features of ESCC (PIK3CA mutation, p53 expression, and LINE-1 methylation level). The immunoreactivity and mRNA level of APOBEC3B were significantly higher in cancer tissues than in noncancerous esophageal mucosae (P = 0.050). APOBEC3B expression was significantly correlated with PIK3CA mutation (P = 0.013), particularly with C to T transitions of PIK3CA (P = 0.041). Moreover, a high expression of APOBEC3B was significantly associated with LINE-1 hypomethylation (P = 0.027). Given the crucial roles of PIK3CA mutation and LINE-1 methylation levels, our findings might provide new insights into the biological mechanisms of ESCC tumorigenesis and progression.