Exosomal microRNAs derived from colon cancer cells promote tumor progression by suppressing fibroblast TP53 expression

The tumor microenvironment offers favorable conditions for tumor progression, and activated fibroblasts, known as cancer‐associated fibroblasts, play a pivotal role. TP53‐deficient cancer cells are known to induce strong fibroblast activation. We aimed to elucidate the oncogenic role of exosomes derived from TP53‐deficient colon cancer cells in fibroblast proliferation and tumor growth. Cancer cell‐derived exosomes (CDEs) were isolated from the conditioned media of cancer cells using a sequential ultracentrifugation method. The effects of exosomes on tumor growth were evaluated using human cell lines (TP53‐WT colon cancer, HCT116; TP53‐mutant colon cancer, HT29; and fibroblasts, CCD‐18Co and WI‐38) and an immune‐deficient nude mouse xenograft model. HCT116 (HCT116^{sh p53}) cells deficient in TP53 accelerated cocultured fibroblast proliferation compared to TP53‐WT HCT116 (HCT116^{sh control}) cells in vitro. Exosomes from HCT116^{sh p53} cells suppressed TP53 expression of fibroblasts and promoted their proliferation. Xenografts of HCT116^{sh p53} cells grew significantly faster than those of HCT116^{sh control} cells in the presence of co‐injected fibroblasts, but this difference was diminished by CDE inhibition. Microarray analysis identified upregulation of several microRNAs (miR‐1249‐5p, miR‐6737‐5p, and miR‐6819‐5p) in TP53‐deficient CDEs, which were functionally proven to suppress TP53 expression in fibroblasts. Exosomes derived from TP53‐mutant HT29 cells also suppressed TP53 expression in fibroblasts and accelerated their growth. The proliferative effect of HT29 on cocultured fibroblasts was diminished by inhibition of these miRNAs in fibroblasts. Our results suggest that CDEs play a pivotal role in tumor progression by fibroblast modification. Cancer cell‐derived exosomes might, therefore, represent a novel therapeutic target in colon cancer.     

Potent in vitro and in vivo antitumor effects of MDM2 inhibitor nutlin-3 in gastric cancer cells

The tumor suppressor gene p53 is the most frequently mutated gene in human cancers. However, its mutation rate is relatively low in gastric cancer compared with other cancers. In this study, we investigated the mechanisms underlying the antitumor effects of nutlin-3, an inhibitor of human homolog of murine double minute 2 (MDM2). MDM2 is a negative regulator of p53. Four gastric cancer cell lines with wild-type p53 (wt p53) and three with mutant-type p53 (mt p53) were analyzed for MDM2 and MDM4 expression by immunoblotting, and for their gene amplification by quantitative real-time PCR. Moreover, the viability of cells exposed to nutlin-3 was examined by WST-8 assay, and the expression of p53 and its downstream genes was analyzed by immunoblotting. Nutlin-3 stabilized p53 and increased the expression of p21(WAF1) and Noxa, and cleaved poly (ADP)-ribose polymerase regardless of the pre-expression levels of MDM2 and MDM4 in gastric cancer cells with wt p53. Flow cytometry revealed that nutlin-3 arrested the cell cycle in G(1) phase and induced apoptosis in the cell lines. These nutlin-3 effects were not observed in the cell lines with mt p53. Nutlin-3 exerted additive or synergistic cytotoxicity in combination with 5-fluorouracil or cisplatin in most cell lines with wt p53. An in vivo antitumor effect of nutlin-3 alone and its additive augmentation by 5-fluorouracil were confirmed in an MDM2 overexpressed xenograft tumor model. Nutlin-3 showed potent antitumor activity against human gastric cancer cells with wt p53 and shows promise as a single agent and in combination with conventional anticancer drugs.     

Correlation of TP53 and MDM2 genotypes with response to therapy in sarcoma

BACKGROUND:

Relatively few sarcomas harbor TP53 (tumor protein p53) mutations, but in many cases, amplification of MDM2 (murine double minute 2) effectively inactivate p53. The p53 pathway activity can also be affected by normal genetic variation.

METHODS:

The mutation status of TP53 and expression of MDM2, TP53, and their genetic variants SNP309 and R72P (Arg72Pro) were investigated in 125 sarcoma patient samples and 18 sarcoma cell lines. Association of the different genotypes and gene aberrations with chemotherapy response and survival, as well as response to MDM2 antagonists in vitro was evaluated.

RESULTS:

Twenty‐two percent of the tumors had mutant TP53 and 20% MDM2 gene amplification. Patients with wild‐type TP53 (TP53^Wt) tumors had improved survival (P < .001) and TP53^Wt was an independent prognostic factor (hazard ratio = 0.41; 95% confidence interval = 0.23‐0.74; P = .03). Interestingly, there was a trend toward longer time to progression after chemotherapy for tumors with the apoptosis‐prone p53 variant R72 (P = .07), which was strongest with doxorubicin/ifosfamide‐based regimens (P = .01). Liposarcomas had low R72 frequency (33% versus 56%), but increased levels of MDM2 and MDM4 (51% and 11%, P < .001). MDM2 overexpression on a TP53^Wt background predicted better response to MDM2 antagonist Nutlin‐3a, irrespective of R72P or SNP309 status.

CONCLUSIONS:

Improved survival after chemotherapy was found in patients with TP53^Wt tumors harboring the R72 variant. MDM2 overexpression in TP53^Wt tumors predicted good response to MDM2 antagonists, irrespective of R72P or SNP309 status. Thus, detailed TP53 and MDM2 genotype analyses prior to systemic therapy are recommended. Cancer 2013. © 2012 American Cancer Society.     

Efficacy of MDM2 inhibitor MI-219 against lung cancer cells alone or in combination with MDM2 knockdown, a XIAP inhibitor or etoposide

The p53 tumor suppressor is negatively regulated by murine double minute 2 (MDM2), which binds to p53 and promotes p53 ubiquitination and degradation. MDM2 inhibitor-219 (MI-219), a small molecule MDM2 inhibitor, was recently reported to disrupt p53-MDM2 binding, leading to p53 activation and suppression of tumor cell growth both in vitro and in vivo. This study tested the efficacy of MI-219 against a panel of lung cancer cell lines alone or in combination with MDM2 knockdown, an X-linked inhibitor of apoptosis protein (XIAP) inhibitor, or a chemotherapeutic drug, etoposide. When acting alone, MI-219 selectively inhibited growth of wild-type (wt) p53-containing lung cancer cells by induction of G1 or G2 arrest in a p53-dependent manner, but had a minor effect on wt p53-bearing immortalized cells. MDM2 knockdown had a minimal effect on MI-219 induced growth suppression. Although MI-219 increased XIAP expression, blockage of XIAP via SM-164, a Smac mimetic compound, did not selectively enhance MI-219 cytotoxicity. Significantly, MI-219 sensitized lung cancer cells to etoposide-induced cell killing. This study revealed that, when acting alone, MI-219 selectively inhibits the growth of lung cancer cells harboring a wt p53. In combination, MI-219-induced cytotoxicity was not affected by MDM2 knockdown nor by a XIAP inhibitor, but MI-219 sensitized cancer cells to etoposide, suggesting MI-219 could serve as a chemosensitizing agent.     

S‐MDM4 mRNA overexpression indicates a poor prognosis and marks a potential therapeutic target in chronic lymphocytic leukemia

The purpose of the present study was to investigate the prognostic significance of murine double minute 4 (MDM4) in chronic lymphocytic leukemia (CLL) and to characterize the role of MDM4 in the p53 pathway. Full‐length MDM4 (FL‐MDM4), a splicing variant of MDM4 (S‐MDM4) and murine double minute 2 (MDM2) mRNA expressions were detected by quantitative PCR in 140 Chinese patients with CLL, and primary CLL cells were treated in vitro with either fludarabine or Nutlin‐3 to explore the interaction between p53 status and MDM4 or MDM2 expression. A marked increase of FL‐MDM4 and S‐MDM4 expressions were observed in the CLL patients with p53 aberrations (deletion and/or mutation) (P = 0.024, P < 0.001). A high level of S‐MDM4 mRNA expression was associated with short treatment free survival (TFS) (P = 0.004). FL‐MDM4 expression was significantly decreased after fludarabine treatment (P = 0.001) but increased after Nutlin‐3 treatment (P = 0.008) of primary CLL cells without p53 aberrations. Both S‐MDM4 and MDM2 expressions were significantly increased after fludarabine treatment of CLL cells without p53 aberrations (P = 0.013 and P = 0.030). MDM2 overexpression also occurred in CLL cells with p53 wild type after Nutlin‐3 treatment (P = 0.018). FL‐MDM4 and S‐MDM4 overexpression are indicators of p53 aberrations in CLL patients, suggesting that those patients have a poor prognosis. FL‐MDM4 inhibitory effects on p53 can be removed by MDM2‐p53 and saved by Nutlin‐3.     

茯苓酸通过调控AKT/MDM2/p53通路影响结直肠癌HCT116细胞的恶性生物学行为

目的：探究茯苓酸（PA）是否通过AKT/MDM2/p53通路影响结直肠癌HCT116细胞的恶性生物学行为。方法：常规培养HCT116细胞,并将其分为对照组、MK-2206(AKT抑制剂)组、PA低浓度（PA-L）组、PA高浓度（PA-H）组、PA-H+SC79(AKT激活剂)组。CCK-8法、细胞克隆形成实验、流式细胞术、Transwell、qPCR法和WB法实验分别检测各组HCT116细胞的增殖活力,克隆形成能力,细胞凋亡,迁移、侵袭能力,E-cadherin、N-cadherin和vimentin mRNA表达以及AKT/MDM2/p53通路相关蛋白的表达。结果：PA可明显抑制HCT116细胞的增殖活力（P<0.05）、克隆形成能力（P<0.05）、迁移和侵袭能力（P<0.05）,诱导其凋亡（P<0.05）,抑制N-cadherin、vimentin mRNA的表达（P<0.05）,促进E-cadherin mRNA的表达（P<0.05）,抑制AKT、MDM2的磷酸化水平（P<0.05）,促进p53蛋白的表达（P<0.05）;AKT抑...     

TLR3 induction by anticancer drugs potentiates poly I:C‐induced tumor cell apoptosis

Toll‐like receptor 3 (TLR3) has gained recognition as a novel molecular target for cancer therapy because TLR3 activation by its synthetic ligand poly I:C directly causes tumor cell death. Recently, we reported that tumor suppressor p53 increases the expression of TLR3 in several tumor cell lines. Another study also showed that interferon‐α (IFN‐α) up‐regulates TLR3 expression. We thus hypothesized that various anticancer drugs such as p53‐activating reagents and IFNs may potentiate poly I:C‐induced tumor cell death through the up‐regulation of TLR3 expression. Here, we screened several anticancer drugs that, together with poly I:C, effectively cause tumor cell death in colon carcinoma HCT116 cells. We found that the DNA‐damaging reagent 5‐fluorouracil (5‐FU) increased TLR3 mRNA expression and potentiated poly I:C‐induced apoptosis in HCT116 p53^+/+ cells but had only minimal effect in p53^?/? cells, indicating a p53‐dependent pathway. On the other hand, IFN‐α increased poly I:C‐induced apoptosis and the TLR3 mRNA level in HCT116 p53^+/+ and p53^?/? cell lines. Furthermore, the combination of poly I:C, 5‐FU and IFN‐α induced the highest apoptosis in HCT116 p53^+/+ and p53^?/? cells. Taken together, these data suggest that the anticancer drugs increased TLR3 expression and subsequently potentiated poly I:C‐induced apoptosis likely via p53‐dependent and ‐independent pathways. Considering that the p53 status in malignant cells is heterogeneous, this combination approach may provide a highly effective tumor therapy. (Cancer Sci 2010)     

Polymorphisms at p53, p73, and MDM2 loci modulate the risk of tobacco associated leukoplakia and oral cancer

Polymorphisms at loci controlling cellular processes such as cell cycle, DNA repair, and apoptosis may modulate the risk of cancer. We examined the association of two linked polymorphisms (G4C14–A4T14) at p73 and one polymorphism (309G > T) at MDM2 promoter with the risk of leukoplakia and oral cancer. The p73 and MDM2 genotypes were determined in 197 leukoplakia patients, 310 oral cancer patients and in 348 healthy control subjects. The p73 GC/AT genotype increased the risk of leukoplakia (OR = 1.6, 95% CI = 1.1–2.3) and oral cancer (OR = 2.4, 95% CI = 1.7–3.3) but the 309G > T MDM2 polymorphism independently could not modify the risk of any of the diseases. Stratification of the study population into subgroups with different tobacco habits showed that the risk of the oral cancer is not modified further for the individuals carrying p73 risk genotype. However, leukoplakia patients with smokeless tobacco habit showed increased risk with combined GC/AT and AT/AT (OR = 3.0, 95% CI = 1.3–7.0) genotypes. A combined analysis was done with our previous published data on p53 codon 72 pro/arg polymorphism. Analysis of pair wise genotype combinations revealed increase in risk for specific p73‐MDM2 and p73‐p53 genotype combinations. Finally, the combined three loci analyses revealed that the presence of at least one risk allele at all three loci increases the risk of both leukoplakia and oral cancer. © 2009 Wiley‐Liss, Inc.     

MDM2 SNP309 contributes to non-small cell lung cancer survival in Chinese

Murine double minute 2 (MDM2) is a negative regulator of the tumor suppressor gene p53. Single nucleotide polymorphisms in MDM2 and p53 can affect patient's response to chemotherapy as well as overall survival of many cancers. This study aimed to assess the associations between polymorphisms in MDM2 and p53 and survival of non‐small cell lung cancer (NSCLC) patients in Chinese. We selected and genotyped both potentially functional SNPs and tagging SNPs in MDM2 and p53 using Illumina Golden Gate platform in a cohort of 568 NSCLC patients. Associations between genotypes and NSCLC median survival time (MST) were assessed using the Kaplan–Meier method. Cox proportional hazard models were performed with the adjustment for age, stage, smoking, histology, surgical operation, and chemo‐ or radiotherapy status. We found that the MDM2 SNP309 (rs2279744) GT/TT genotypes were associated with a significantly worse survival (MST: 23.0 mo for GT/TT vs. 33.0 mo for GG; log‐rank P = 0.028). In the multivariate Cox regression analyses, the MDM2 SNP309GT/TT genotypes were associated with a 1.42‐fold [HR = 1.42, 95% confidence interval (CI), 1.09–1.84] increased risk of death of NSCLC, compared with SNP309GG genotype. MDM2 SNP309 may be used as one of the candidate biomarkers to predict NSCLC survival. © 2011 Wiley‐Liss, Inc.     

Preclinical evaluation of the first intravenous small molecule MDM2 antagonist alone and in combination with temozolomide in neuroblastoma

High-risk neuroblastoma, a predominantly TP53 wild-type (wt) tumour, is incurable in >50% patients supporting the use of MDM2 antagonists as novel therapeutics. Idasanutlin (RG7388) shows in vitro synergy with chemotherapies used to treat neuroblastoma. This is the first study to evaluate the in vivo efficacy of the intravenous idasanutlin prodrug, RO6839921 (RG7775), both alone and in combination with temozolomide in TP53 wt orthotopic neuroblastoma models. Detection of active idasanutlin using liquid chromatography-mass spectrometry and p53 pathway activation by ELISA assays and Western analysis showed peak plasma levels 1 h post-treatment with maximal p53 pathway activation 3–6 h post-treatment. RO6839921 and temozolomide, alone or in combination in mice implanted with TP53 wt SHSY5Y-Luc and NB1691-Luc cells showed that combined RO6839921 and temozolomide led to greater tumour growth inhibition and increase in survival compared to vehicle control. Overall, RO6839921 had a favourable pharmacokinetic profile consistent with intermittent dosing and was well tolerated alone and in combination. These preclinical studies support the further development of idasanutlin in combination with temozolomide in neuroblastoma in early phase clinical trials.     

p53 and MDM2 in renal cell carcinoma

Renal cell carcinoma (RCC) is the most common type of kidney cancer and follows an unpredictable disease course. To improve prognostication, a better understanding of critical genes associated with disease progression is required. The objective of this review was to focus attention on 2 such genes, p53 and murine double minute 2 (MDM2), and to provide a comprehensive summary and critical analysis of the literature regarding these genes in RCC. Information was compiled by searching the PubMed database for articles that were published or e‐published up to April 1, 2009. Search terms included renal cancer, renal cell carcinoma, p53, and MDM2. Full articles and any supplementary data were examined; and, when appropriate, references were checked for additional material. All studies that described assessment of p53 and/or MDM2 in renal cancer were included. The authors concluded that increased p53 expression, but not p53 mutation, is associated with reduced overall survival/more rapid disease progression in RCC. There also was evidence that MDM2 up‐regulation is associated with decreased disease‐specific survival. Two features of RCC stood out as unusual and will require further investigation. First, increased p53 expression is tightly linked with increased MDM2 expression; and, second, patients who have tumors that display increased p53 and MDM2 expression may have the poorest overall survival. Because there was no evidence to support the conclusion that p53 mutation is associated with poorer survival, it seemed clear that increased p53 expression in RCC occurs independent of mutation. Further investigation of the mechanisms leading to increased p53/MDM2 expression in RCC may lead to improved prognostication and to the identification of novel therapeutic interventions. Cancer 2010. © 2010 American Cancer Society.     

Combined effects of MDM2 SNP309 and TP53 R72P polymorphisms, and soy isoflavones on breast cancer risk among Chinese women in Singapore

The MDM2 oncoprotein regulates the p53 pathway and, while functional polymorphisms of the MDM2 and p53 genes have been investigated for association with breast cancer risk, results are largely null or non-conclusive. We have earlier reported that the increased intake of soy isoflavones reduces risk of postmenopausal breast cancer, and experimental studies suggest that dietary isoflavones can down-regulate the expression of the MDM2 oncoprotein. In this study, we investigated the association between the MDM2 SNP309 and TP53 R72P polymorphisms and breast cancer risk using a case–control study of 403 cases and 662 controls nested among 35,303 women in The Singapore Chinese Health Study, a population-based, prospective cohort of middle-aged and elderly men and women who have been continuously followed since 1993. The G allele of the TP53 R72P polymorphism and T allele of the MDM2 SNP309 polymorphism were putative high-risk alleles and exhibited a combined gene–dose-dependent joint effect on breast cancer risk that was more clearly observed in postmenopausal women. Among postmenopausal women, the simultaneous presence of G allele in TP53 and T allele in MDM2 polymorphisms was associated with an odds ratio (OR) of 2.42 [95% confidence interval (CI) 1.06–5.50]. Furthermore, the protective effect of dietary soy isoflavones on postmenopausal breast cancer was mainly confined to women homozygous for the high activity MDM2 allele (GG genotype). In this genetic subgroup, women consuming levels of soy isoflavones above the median level exhibited risk that was half of those with below median intake (OR 0.52; 95% CI 0.28–0.99). Our findings support experimental data implicating combined effects of MDM2 protein and the p53-mediated pathway in breast carcinogenesis, and suggest that soy isoflavones may exert protective effect via down-regulation of the MDM2 protein.     

Rare MDM4 gene amplification in colorectal cancer: The principle of a mutually exclusive relationship between MDM alteration and TP53 inactivation is not applicable

MDM4, a homolog of MDM2, is considered a key negative regulator of p53. Gene amplification of MDM4 has been identified in a variety of tumors. MDM2 or MDM4 gene amplification is only associated with the wild-type TP53 gene in retinoblastomas, thus the amplification of the two genes is mutually exclusive. Previously, we demonstrated that MDM2 amplification and TP53 alteration were not mutually exclusive in colorectal cancer, and we identified a subset of colorectal cancer patients without alterations in either the TP53 or the MDM2 gene. In this study, we investigated the gene amplification status of MDM4 in the same set of colorectal cancer cases. Unexpectedly, MDM4 amplification was rare, detected in only 1.4% (3 out of 211) of colorectal cancer cases. All the three gene-amplified tumors also harbored TP53-inactivating mutations. This contradicts the simple mutually exclusive relationship observed in retinoblastomas. Surprisingly, two of the three MDM4-amplified tumors also demonstrated MDM2 amplification. Paradoxically, the MDM4 protein levels were decreased in the tumor tissue of the gene-amplified cases compared with levels in the matched normal mucosa. We speculate that MDM4 might play a role in colorectal carcinogenesis that is not limited to negative regulation of p53 in combination with MDM2. The functional significance of MDM4 is still unclear and further studies are needed.     

Combinatorial inhibition of Plk1 and PKCβ in cancer cells with different p53 status

PKCβ and Plk1 are fascinating targets in cancer therapy. Therefore, we combined Enzastaurin targeting PKCβ and SBE13 targeting Plk1 to test synergistic effects in cells with different p53 status. We analyzed cell proliferation and apoptosis induction, and did Western blot and FACScan analyses to examine the combined PKCβ and Plk1 inhibition. p53-wild-type cells are more resistant to the combinatorial treatment than p53-deficient cells, which displayed a synergistic reduction of cell proliferation after the combination. HeLa, MCF-7 and HCT116^p53wt and HCT116^p53-/- cells differed in their cell cycle distribution after combinatorial treatment in dependence on a functional p53-dependent G1/S checkpoint (p53-deficient cells showed an enrichment in S and G2/M, p53-wild-type cells in G0/G1 phase). hTERT-RPE1 cells did not show the synergistic effects of cancer cells.Thus, we demonstrate for the first time that Plk1 inhibition using SBE13 enhances the effects of Enzastaurin in cancer cells. HCT116^p53wt and HCT116^p53-/- cells confirmed the p53-dependence of different effects after Plk1 and PKCβ inhibition observed in HeLa and MCF-7 cells. Obviously, p53 protects cells from the cytotoxicity of Enzastaurin in combination with SBE13. For that reason this combination can be useful to treat p53-deficient cancers, without displaying toxicity to normal cells, which all have functional p53.     

Epstein‐Barr virus‐encoded EBNA‐5 forms trimolecular protein complexes with MDM2 and p53 and inhibits the transactivating function of p53

We report that MDM2, a negative regulator of p53, can bind to EBNA‐5. Using GST pull‐down assay, immunoprecipitation, surface plasmon resonance and immunostaining of lymphoblastoid cells, we found that trimolecular complexes are formed between EBNA‐5, MDM2 and p53, where MDM2 serves as a bridge. The EBNA‐5 binding to MDM2 counteracted destabilizing effect of the latter on the p53. In ubiquitination and degradation assays in vitro, EBNA‐5 inhibited p53 polyubiquitination (but not monoubiquitination) in a concentration‐dependent manner. This resembles the effect of p14ARF on p53. Moreover, EBNA‐5 was found to inhibit the degradation of p53 in vitro. High levels of p53 expression were maintained in LCLs. The binding of EBNA‐5 to MDM2 also could impair the functional activity of p53. The p53‐dependent genes P21 and VDR were not induced in EBV‐infected, in contrast to mitogen‐activated cells. This may explain the tolerance of established LCLs to high levels of p53 without undergoing apoptosis.     

Combination of p53 codon 72 polymorphism and inactive p53 mutation predicts chemosensitivity to 5‐fluorouracil in colorectal cancer

There are increasing reports showing the clinical significance of the p53 polymorphism status in terms of the response to chemotherapy. We investigated whether p53 polymorphism and mutation were associated with in vitro sensitivity to 5‐fluorouracil (5‐FU) in patients with colorectal cancer. Chemosensitivity to 5‐FU was evaluated by the collagen gel droplet embedded culture drug sensitivity test. 5‐FU sensitivity of tumor cells without inactive p53 mutation in the arginine/arginine (Arg/Arg) variant was significantly higher than that of tumor cells with or without inactive p53 mutation in other variants (p = 0.022), whereas the 5‐FU sensitivity of tumor cells with inactive p53 mutation in the Arg/Arg variant was significantly lower than that of tumor cells with or without inactive p53 mutation in other variants (p = 0.002). In the Arg/Arg variant, apoptotic cells induced by 5‐FU treatment in patients without inactive p53 mutation were more markedly increased than those in patients with inactive p53 mutation (p = 0.037). Bax and Bcl‐2 protein expressions in tumor tissue treated with 5‐FU were associated with both 5‐FU sensitivity and the apoptotic cell count. Our data show that the Arg/Arg genotype without inactive p53 mutation could be predictive of a more favorable response and the Arg/Arg genotype with inactive p53 mutation a less favorable response to chemotherapy using 5‐FU in CRC. The combination of the p53 codon 72 polymorphism and p53 mutation status is a potential predictive marker of sensitivity to 5‐FU in CRC.     

Activation of AKT and nuclear accumulation of wild type TP53 and MDM2 in anal squamous cell carcinoma

Human papilloma virus (HPV) infection is considered as an important aetiological factor for anal squamous cell carcinoma (ASCC) but is not sufficient for tumour progression. This carcinoma is poorly understood at the molecular level. Using the largest cohort of cases to date we investigated the molecular mechanisms underlying ASCC development, in particular the roles of TP53, MDM2 and AKT. Viral infection in our cohort occurred at high frequency (73%, 94/128) with HPV16 accounting for the majority (86%, 81/94) of infected cases. Only 4% (5/119) of ASCCs showed TP53 (exons 5-8) mutations, but a high frequency (91%, 100/110) of nuclear protein expression of TP53 was observed. There was a significant association (p < 0.001) between nuclear accumulation of TP53 and MDM2 protein although no MDM2 mutations were found, and copy number was normal. Cellular accumulation of phosphorylated-AKT was observed in 66% (82/125) of ASCCs and an association demonstrated between nuclear accumulation of MDM2 and activated AKT (p < 0.001). We observed a high frequency of copy number gain at PIK3CA (47%), and some coding sequence mutations (4%). Amplification of PIK3CA was associated with presence of phosphorylated-AKT (p= 0.008). There was no association between virus infection and TP53 nuclear accumulation (p = 0.5). However, a significant association was found between infection and MDM2 nuclear staining, and between infection and activated AKT (p = 0.04, p = 0.01, respectively). We propose that activation of AKT, possibly through the PI3K-AKT pathway, is an important component of ASCC tumorigenesis that contributes to MDM2 and TP53 accumulation in the nucleus.