B-Raf mutation: A key player in molecular biology of cancer

B-Raf is one of the more commonly mutated proto-oncogenes implicated in the development of cancers. In this review, we consider the mechanisms and clinical impacts of B-Raf mutations in cancer and discuss the implications for the patient in melanoma, thyroid cancer and colorectal cancer, where B-Raf mutations are particularly common.     

Evaluation of the expression of C-kit (CD117) in ependymomas and oligodendrogliomas

C-kit is a proto-oncogene located on the long arm of chromosome 4. Its product, CD117, is a specific immunohistochemical (IHQ) marker that is associated with response to a potent tyrosine kinase inhibitor therapy with STI-571 (Gleevec®) in chronic myelogenous leukemia and GISTs. In our study, we aimed to evaluate the expression of CD117 in glial tumors as this finding may guide therapeutic approaches for these brain tumors. Ependymomas and oligodendrogliomas, in formalin fixed and paraffin embedded blocks were assayed for CD117 immunoreactivity using anti-c-kit (CD117, DAKO). GISTs were used as positive control. We observed immunoreactivity of CD117 protein in 25.5% of tumors in both histological types. In oligodendrogliomas, there was an association between older age at diagnosis and positivity for CD117 (P = 0.039). In addition, we observed an association between higher tumor grade (grade III) and positivity for CD117 (P = 0.007). No clinical association was observed in ependymomas (P > 0.05). This study encourages further investigations, considering that CD117 may be a possible oncogenic factor in some glial tumors. In this case, tumors that express this marker may eventually benefit from a therapy with selective inhibitors of receptor kinases.     

CD117 expression in normal, neoplastic, inflammatory, and reactive lesions of the thyroid

The mutations of c-kit gene, which encodes a transmembrane receptor tyrosine kinase (CD117-KIT) or activation of CD117, lead to the activation of signal transduction cascades regulating cell proliferation, apoptosis, chemotaxis, and adhesion.

The aim of this study was to investigate the expression of CD117 in normal, inflammatory, neoplastic, and reactive lesions of the thyroid.

Using polyclonal anti-CD117 antibody, we performed immunohistochemical staining on tissue blocks from 230 cases obtained from the archives of the Department of Pathology, Ondokuz Mayıs University (Samsun, Turkey), collected between 1990 and 2006.

Each slide was evaluated for extent and intensity of staining. Staining extent was expressed as the percentage of stained cells. Staining of <10% of the cells was accepted as negative. Staining intensity was evaluated only in positive cases. By addition of the extent and intensity scores, the combined score was calculated.

In our study, the combined CD117 staining scores of neoplastic and inflammatory groups were found to be higher than the reactive and normal groups. Within the neoplastic group, papillary carcinomas differed from follicular adenomas significantly, although papillary carcinomas showed no statistically significant difference compared to follicular carcinomas.

Immunohistochemical CD117 positivity was detected in a wide range of neoplastic and inflammatory thyroid diseases. The neoplastic group and, within them, the papillary carcinomas showed a higher ratio of CD117 positivity. Although our results need to be confirmed by other molecular and genetic studies, the high rate of positivity in papillary carcinomas was one of the striking findings, which may result in novel diagnostic and therapeutic approaches.     

Immunohistochemical expression of CD117 and vascular endothelial growth factor in retinoblastoma: possible targets of new therapies

CD117 (C-kit) is thought to play an important role in tumourigenesis. There are limited data in the literature concerning C-kit expression in retinoblastoma. To date, no immunohistochemical studies have been performed to assess the possible association of C-kit with vascular endothelial growth factor (VEGF) in retinoblastoma. This study was designed to investigate C-kit and VEGF immunoexpression in retinoblastoma, their relationship with prognostic parameters as well as the correlation between them. A prospective immunohistochemical study was conducted on 56 retinoblastoma cases. Patients who had received preoperative chemotherapy were excluded. Positive C-kit and VEGF immunoreactivity was observed in 48.2% and 76.8% of retinoblastoma cases respectively. No C-kit immunostaining was seen in the adjacent uninvolved retina. However, VEGF expression was detected within its vasculature. Retinoblastomas with combined pattern of tumour growth revealed a highly significant positive C-kit expression (P = 0.002) compared to cases with endophytic or exophytic growths. Also, positive C-kit expression was statistically higher in cases with optic nerve invasion (P = 0.001) and choroidal invasion (P ≤ 0.01) compared to negative cases. A highly significant positive VEGF expression was detected in cases with optic nerve invasion (P = 0.013) compared to negative cases. Moreover, a highly significant positive correlation was detected between C-kit and VEGF expression (P = 0.006). C-kit is a feature of more aggressive retinoblastomas, with increased expression in tumours spreading beyond the retina. Moreover, VEGF is vastly expressed in retinoblastoma and is associated with optic nerve invasion. Both C-kit and VEGF may represent potential therapeutic targets for retinoblastomas.     

CD117在急性白血病中的表达及临床意义

目的探讨CD117在急性白血病中的表达及其临床意义。方法应用CD45/SSC设门,直接荧光标记法,经流式细胞术对73例急性髓系白血病（AML）和47例急性淋巴细胞白血病（ALL）进行CD117的检测。结果对照组、ALL及AML3组CD117的表达阳性率差异有统计学意义（χ2=41.681,P﹤0.01）。AML组CD117的表达阳性率（58.9%）明显高于对照组（0）及ALL组（8.5%）。CD117/CD34的共表达率ALL组明显低于AML组（4.3%vs45.2%,P﹤0.05）。AML组CD117＋患者的CR率为60.5%,CD117-患者为76.7%,两者比较差异无统计学意义（P〉0.05）;而CD117＋/CD34＋患者的CR率为54.5%,明显低于CD117-/CD34-患者的CR率（88.2%,P﹤0.05）。结论 CD117可作为辅助诊断AML的髓系标志抗原,CD34＋/CD117＋可作为进一步排除ALL的指标。CD117＋/CD34＋可能是AML中一类预后不良的特殊亚型,可以作为AML预后判断的指标之一。     

Prognostic value of CD117 in cancer: a meta-analysis

Background: The prognostic value of CD117 expression in cancers has been evaluated for several years while the results remain controversial. We thus performed a systematic review and meta-analysis of studies assessing the impact of CD117 expression on overall survival (OS) and disease-free survival (DFS) to clarify this issue. Methods: We searched Pubmed, Embase and Web of Science to identify studies on the prognostic impact of CD117 expression in cancers. A total of 4,458 patients from 39 eligible studies were included in the analysis. Pooled risk ratios (RRs) with 95% confidence interval (95% CI) were calculated to estimate the effect using random-effects model. Results: The analysis indicated that CD117 had significant association with poor OS of osteosarcoma (OR=1.36, 95% CI=1.03-1.79, I2=0%, fixed model) and renal carcinoma (OR=4.86, 95% CI=2.72-8.67, I2=0%, fixed model).However, no significant association between CD117 and DFS was found in overall studies. Conclusions: CD117 expression might be a predictive factor of poor prognosis in some surgically treated cancers, particularly in renal carcinoma.     

CD117+ small cell lung cancer lacks the asp 816-->val point mutation in exon 17

AIMS: To determine the frequency of point mutation in c-kit in CD117+ small cell lung cancer (SCLC). A significant proportion of SCLCs have been documented to be CD117+, thereby signifying they express the c-kit gene product. This finding suggests this tumour may be a potential target for tyrosine kinase inhibitor (TKI) agents directed at c-kit. A point mutation in exon 17 of the c-kit gene, however, can abrogate the binding of TKIs. This being the case, immunohistochemistry is necessary to identify potential candidates for treatment with TKIs, but DNA sequence analysis may need to be performed to determine if these tumours will respond. METHODS AND RESULTS: Tumour cells of 23 cases of SCLC showing immunoreactivity for CD117 were laser capture microdissected from archived formalin-fixed paraffin-embedded tissue and the DNA isolated. PCR on exon 17 of the c-kit gene was performed and the amplified product sequenced. No point mutations were detected. CONCLUSIONS: The absence of mutations in exon 17 of CD117+ SCLC suggests this tumour may respond to therapy with TKI.     

Rare KIT (CD117) expression in multiple myeloma abrogates the usefulness of imatinib mesylate treatment

Background Imatinib mesylate blocks the tyrosine kinase activity of KIT (CD117) and is an effective treatment for gastrointestinal stromal tumors. In multiple myeloma, KIT expression has been detected by flow cytometry in about 33% of specimens, but no previous immunohistochemical assessment has yet been made of the expression pattern of KIT.Materials and methods We performed immunohistochemical analyses of 100 patients, including 72 with multiple myeloma (MM), 8 with lymphoplasmacytic lymphoma (LPL), 10 with monoclonal gammopathy of undetermined significance (MGUS) and 10 with reactive plasmocytosis. One KIT-positive MM was sequenced using polymerase chain reaction analysis.Results In MM, only 2 cases (2.8%) were KIT positive. The great majority of the cases (97, 2%) did not express the KIT receptor tyrosine kinase. No mutation of the c-kit gene was detected.Conclusions KIT expression is a rare event in MM and not detectable in MGUS and LPL. Therefore, treatment with imatinib is unlikely to be effective in these patients.     

A CD40 and an NCOA5 gene polymorphism confer susceptibility to psoriasis in a Southern European population: a case-control study

Recent genome-wide association studies of many complex diseases have successfully identified novel susceptibility loci, with many of them shared by multiple disease-associated pathways. The genes CD40 and nuclear receptor coactivator 5 (NCOA5), located in a 400-kb region surrounding CD40, have been reported to be associated with increased risk for rheumatoid arthritis and other autoimmune diseases. We hypothesized that those genes may also have a role in psoriasis (PS), an autoimmune, chronic inflammatory skin disease. In a case-control study, 198 patients with PS and 400 controls were genotyped for 2 single nucleotide polymorphisms (SNPs) of the CD40 and NCOA5 genes located on chromosome 20q.12-q13.12. Here, we demonstrate for the first time the association of both SNPs with susceptibility to PS, thus suggesting a putative key role of both genes in multiple autoimmune diseases. Alleles G and C of the CD40 rs4810485 and NCOA5 rs2903908 SNPs, respectively, were more common in individuals with PS than in controls (p = 0.03, odds ratio [OR] = 1.42, 95% confidence interval [95% CI] 1.05-1.95 and p = 0.000 003, OR = 1.93, 95% CI 1.47-2.55, respectively). The identification of shared genetic susceptibility loci may provide insight into our understanding of the pathophysiology of autoimmune diseases.     

Gastrointestinal Kaposi's sarcoma: CD117 expression and the potential for misdiagnosis as gastrointestinal stromal tumour

Aims:  Gastrointestinal Kaposi's sarcoma (KS) may mimic gastrointestinal stromal tumours (GISTs) histologically. Studies have shown that KS outside the gastrointestinal (GI) tract may express CD117, an antibody usually used to support a diagnosis of GIST. The aim was to evaluate the clinicopathological features of GI KS, including the expression of CD117 with and without antigen retrieval.
Methods and results:  Fourteen GI KS were assessed histologically, 12 of which were also subjected to immunohistochemistry for CD34, human herpesvirus (HHV) 8, DOG1 and CD117. CD117 immunohistochemistry was performed with and without antigen retrieval. All cases showed an infiltrative spindle cell tumour. Lamina propria infiltration, lymphoplasmacytic inflammation, extravasated red blood cells and haemosiderin were typical histological features. In all cases tumour cells were positive for CD34 and HHV8, but negative for DOG1. CD117 was positive in four of 12 cases without antigen retrieval and 10 of 12 cases with antigen retrieval.
Conclusions:  The microscopic distinction of GI KS from GIST can be difficult. Clues that raise the possibility of GI KS include young patient age, a history of immunosuppression, lamina propria infiltration, lymphoplasmacytic inflammation, extravasated red blood cells and haemosiderin deposition. Use of the immunomarkers CD117 (without antigen retrieval), HHV8 and DOG1 may aid in the distinction between GI KS and GIST.     

CD117 expression in operable oesophageal squamous cell carcinomas predicts worse clinical outcome

Aims

To investigate the aberrant expression of CD117 in oesophageal squamous cell carcinoma (SCC) and its prognostic significance.

Methods and results

Immunohistochemical staining for CD117 was performed on tissue microarray and routine tissue sections from 157 oesophageal SCC patients and 10 normal oesophageal epithelia adjacent to tumour. The positive rate of CD117 expression was 29.9% in oesophageal SCC tissues, whereas no CD117 expression was detected in the 10 normal oesophageal epithelia. CD117 expression was significantly associated with T stage (P < 0.001), distant metastasis (P = 0.015), lymph node metastasis (P = 0.019), and clinical stage (P = 0.021). Progression‐free survival in the patients with CD117‐positive tumours was shorter than that in the patients with CD117‐negative tumours (P = 0.010). In univariate analyses, CD117 expression was the most significant factor for overall survival of oesophageal SCC patients (P < 0.001), followed by lymph node metastasis (P = 0.001), T stage (P = 0.002), clinical stage (P = 0.006), distant metastasis (P = 0.020), and histological grade (P = 0.027). Multivariate analyses verified that CD117 expression was an independent prognostic marker for oesophageal SCC patients (P = 0.002). In addition, CD117 expression predicted poorer survival in patients without distant metastases.

Conclusions

CD117 expression in operable oesophageal SCC may be a valuable prognostic marker, and detection of its expression in clinical samples may be useful in defining a subclass of oesophageal SCCs with extremely poor clinical outcome, which may require a specially targeted treatment modality.     

Sequence analysis and high-throughput immunhistochemical profiling of KIT (CD 117) expression in uveal melanoma using tissue microarrays

We aimed to immunohistochemically examine the expression of KIT (CD 117) in human posterior uveal melanoma and to analyze KIT-positive tumors for gene mutations. Brought into a tissue microarray (TMA) format were 101 formalin-fixed, paraffin-embedded posterior uveal melanomas. Immunhistochemistry was performed using the polyclonal anti-CD117 antibody from Dako (A4502). In ten selected KIT-positive tumors, exons 2, 8, 9, 11, 13 and 17 were sequenced. Of the 101 cases, 89 (88%) could be evaluated on the TMAs. Immunohistochemistry for CD 117 was weakly positive in 5 cases (6%), moderately positive in 10 cases (12%) and strongly positive in 57 cases (69%). No KIT mutations were detected in the analyzed exons. In conclusion, human posterior uveal melanoma frequently expresses CD117 at high levels. Although KIT mutations could not be found, it appears justified to investigate the utility of imatinib mesylate in the treatment of these patients.     

急性早幼粒细胞白血病中CD117和CD34共表达的临床意义

目的：研究CD117和CD34在成人急性非淋巴细胞自血病（Acute nonlymphoblastic leukemia，ANLL）M1～M2型和急性早幼粒细胞白血病（Acute promyelocytic leukemia，arE）M3患者中的表达，重点探讨M3患者CD117和CD34共表达（CD117／CD34共表达）的临床意义。方法：将研究病例分为M1～M2和M3二组，采用流式细胞术（Flow cytometery，FCM）随机检测54例M3和63例M1～M2二组初诊患者骨髓单个核细胞（BMMNC）髓系抗原CD117和干（祖）细胞抗原CD34的表达；比较M1～M2和M3二组ANLL患者中CD117、CD34表达的阳性率的差异，以及CD13、CD33和CD117分别与CD34共表达的阳性率差异。结果：CD117在M1～M2组患者中表达的阳性率是71．4／％（45／63），在M3组表达的阳性率为66．7％（36／54），差异无统计学意义（P=0．58）；CD34在M1～M2和M3二组中表达的阳性率分别为66．7％（42／63）和11．1％（6／54），差异有统计学意义（P=0．000）；二组ANLL的CD117／CD34共表达阳性率分别为71．1％（45／63）和7．4％（4／54），其差异有统计学意义（P=0．000）。结论：CD117可作为AL的髓系免疫学标志，但其在ANLL中的表达缺乏系列内阶段特异性。M3患者的CD34表达和CD117／CD34共表达的阳性率低于M1～M2者；CD117／CD34共表达可作为M1～M2和M3鉴别诊断的免疫学分型参考指标。     

Rare expression of KIT (CD117) in lymphomas: a tissue microarray study of 1166 cases

AIMS: Imatinib mesylate specifically inhibits KIT tyrosine kinase activity, and has been proven to be effective in the treatment of gastrointestinal stromal tumours. Because other KIT-expressing malignancies might benefit from Imatinib therapy, we evaluated the distribution and expression of KIT in 1166 cases of malignant lymphoma. MATERIALS AND RESULTS: Tissue microarrays (TMAs) containing 824 non-Hodgkin's lymphoma (NHL) and 342 Hodgkin's lymphoma (HL) cases were immunohistochemically analysed for the expression of the KIT protein. Two KIT-positive NHLs were sequenced using polymerase chain reaction analysis. One T-cell lymphoma and one follicular lymphoma of the 747 NHL cases (0.3%) were positive for KIT. All HLs were Kit-negative. None of the KIT-positive cases showed a kit gene mutation. CONCLUSIONS: KIT expression is a very rare event in NHL and virtually absent in HL. In the few positive cases, the aberrant expression is not caused by a mutation in the 'hot-spots' of the kit gene, indicating that treatment of these tumours with Imatinib may be ineffective.     

DOG1 and CD117 are the antibodies of choice in the diagnosis of gastrointestinal stromal tumours

Novelli M, Rossi S, Rodriguez‐Justo M, Taniere P, Seddon B, Toffolatti L, Sartor C, Hogendoorn P C W, Sciot R, Van Glabbeke M, Verweij J, Blay J Y, Hohenberger P, Flanagan A & Dei Tos A P
(2010) Histopathology 57 , 259–270
DOG1 and CD117 are the antibodies of choice in the diagnosis of gastrointestinal stromal tumours Aims: The histopathological diagnosis of gastrointestinal stromal tumours (GIST) is typically made based on a combination of clinical and morphological features supported by immunohistochemistry studies. The aim of this study was to examine the staining quality, sensitivity, specificity and utility of antibodies used commonly in GIST diagnosis. Methods and results: Immunohistochemistry with a panel of antibodies [CD117, DOG1, protein kinase C (PKC)‐theta, nestin, CD34, smooth muscle actin (SMA), desmin, S100 and CD171] was performed on whole sections from 187 GIST and 29 gastrointestinal mesenchymal tumours, and on several microarrays including 355 GISTs and 120 soft tissue sarcomas. Results showed that DOG1 and CD117 were the most sensitive and specific antibodies used in GIST diagnosis. PKC‐theta and nestin were sensitive, but less specific, also staining other spindle cell tumours commonly considered in the differential diagnosis of GIST. CD34 staining was less sensitive than many of the other antibodies and of limited aid in diagnosis. The smooth muscle markers SMA and desmin, together with the neural marker S100, were unhelpful in confirming a diagnosis of GIST, but were particularly useful in the exclusion/diagnosis of other gastrointestinal mesenchymal tumour types. Conclusions: In the majority of histologically suspected GISTs a combination of CD117 and DOG1 immunostaining is sufficient to confirm the histological diagnosis.     

人CD59基因的突变和表达及其活性研究

目的: 构建人突变CD59(hmCD59)基因的真核表达系统, 深入研究hmCD59在糖尿病血管并发症中的作用。方法: 分别构建两种含有hmCD59全长cDNA序列的重组pALTER质粒, 运用脂质体介导法, 与pcDNA3质粒共转染CHO细胞, 以G418筛选阳性克隆(编号为hmCD59- 1- CHO及hmCD59 -2- CHO)。应用荧光抗体技术、免疫酶联技术及Westernblot, 进一步检测hmCD59蛋白在转染细胞膜表面的表达。通过双羧乙基碳氧荧光素四乙酰氧甲酯 (BCECF/AM)荧光染料释放试验, 对hmCD59蛋白糖基化前后的抗补体活性进行检测。结果: 筛选出的阳性克隆细胞用荧光抗体技术免疫酶联技术检测表明, 在细胞膜表面有hmCD59分子表达。将细胞的裂解物进行Westernblot证实, 在其相对分子质量(Mr)为 20 000处可见 1条与CD59的Mr相当的蛋白带。BCECF/AM荧光染料释放试验提示, 两种突变质粒的表达产物均具有抗补体活性, 糖基化后活性减弱。结论: 获得两株可稳定表达hmCD59的细胞。表达的hmCD59具有抗补体活性, 但糖基化后活性减弱。     

Characterization of C-Kit (CD117) Expression in Human Normal Pituitary Cells and Pituitary Adenomas

c-kit (CD117) is a tyrosine kinase receptor involved in the proliferation, differentiation, and secretory functions of various cells. In experimental animal models, c-kit has been detected in the pars intermedia of the normal pituitary gland and in alpha-melanocyte-stimulating-hormone-positive adenomas and it has been suggested that it plays a role in regulating adrenocorticotropic hormone (ACTH) secretion. To the best of our knowledge, the expression of c-kit in normal human pituitary cells and in pituitary adenomas has never been reported, so the possible biological role of this receptor in the control of pituitary hormone secretion remains unclear. The aim of this study was to evaluate the immunohistochemical expression of c-kit in normal human pituitary glands and in a series of 62 well-characterized pituitary adenomas. In normal adenohypophyses, several cells, mainly located in the central mucoid wedge, showed a c-kit immunoreactivity (IR). Double label immunostaining procedures showed that the c-kit-IR cells corresponded to ACTH cells. Out of 62 adenomas, 15 (24%) were c-kit-IR, including 7/16 (44%) ACTH cell, 3/7 (42%) null cell, 4/11 (36%) alpha-subunit cell, and 1/11 (10%) follicle-stimulating hormone-luteinizing hormone cell adenomas. By contrast, all ten prolactin cell and seven growth hormone cell adenomas were c-kit negative. These data suggest that, in normal conditions, c-kit may be involved in the pituitary-adrenal axis regulation.