A novel AKT3 mutation in melanoma tumours and cell lines

Recently, a rare activating mutation of AKT1 (E17K) has been reported in breast, ovarian, and colorectal cancers. However, analogous activating mutations in AKT2 or AKT3 have not been identified in any cancer lineage. To determine the prevalence of AKT E17K mutations in melanoma, the most aggressive form of skin cancer, we analysed 137 human melanoma specimens and 65 human melanoma cell lines for the previously described activating mutation of AKT1, and for analogous mutations in AKT2 and AKT3. We identified a single AKT1 E17K mutation. Remarkably, a previously unidentified AKT3 E17K mutation was detected in two melanomas (from one patient) as well as two cell lines. The AKT3 E17K mutation results in activation of AKT when expressed in human melanoma cells. This represents the first report of AKT mutations in melanoma, and the initial identification of an AKT3 mutation in any human cancer lineage. We have also identified the first known human cell lines with naturally occurring AKT E17K mutations

A retrospective analysis of clinical outcome of patients with chemo-refractory metastatic breast cancer treated in a single institution phase I unit

BACKGROUND AND METHODS: Novel approaches to treat chemo-refractory metastatic breast cancer (MBC) are currently under investigation. This retrospective series reviews the outcome of 70 MBC patients who have participated in 30 phase I trials at the Royal Marsden Hospital from 2002 to 2009. RESULTS: The median treatment lines before phase I trial entry for MBC was 5 (range: 1-12 lines). The overall response rate was 11.4% (95% CI: 4.0-18.9%) and the clinical benefit rate at 4 months was 20% (95% CI: 10.6-29.3). The median time to progression was 7.0 weeks (95% CI: 6.4-7.5) and median overall survival was 8.7 months (95% CI: 7.6-9.8) from start of first phase I treatment. No patients discontinued trial because of treatment-related toxicities. Abnormal lactate dehydrogenase, serum albumin <35 mg per 100 ml, >or=5 previous treatment lines, liver metastases and Eastern Cooperative Group performance status >or=2 at study entry were significantly associated with poor overall survival in multivariate analysis. CONCLUSION: This retrospective analysis provides evidence that patients with MBC tolerate phase I clinical trials and a significant proportion of patients with chemo-refractory disease, particularly those with triple-negative or Her2-positive breast cancer, may benefit from treatment

Gene Expression Profiling Reveals New Aspects of PIK3CA Mutation in ERalpha-Positive Breast Cancer: Major Implication of the Wnt Signaling Pathway

BACKGROUND: The PI3K/AKT pathway plays a pivotal role in breast cancer development and maintenance. PIK3CA, encoding the PI3K catalytic subunit, is the oncogene exhibiting a high frequency of gain-of-function mutations leading to PI3K/AKT pathway activation in breast cancer. PIK3CA mutations have been observed in 30% to 40% of ERα-positive breast tumors. However the physiopathological role of PIK3CA mutations in breast tumorigenesis remains largely unclear. METHODOLOGY/PRINCIPAL FINDINGS: To identify relevant downstream target genes and signaling activated by aberrant PI3K/AKT pathway in breast tumors, we first analyzed gene expression with a pangenomic oligonucleotide microarray in a series of 43 ERα-positive tumors with and without PIK3CA mutations. Genes of interest were then investigated in 249 ERα-positive breast tumors by real-time quantitative RT-PCR. A robust collection of 19 genes was found to be differently expressed in PIK3CA-mutated tumors. PIK3CA mutations were associated with over-expression of several genes involved in the Wnt signaling pathway (WNT5A, TCF7L2, MSX2, TNFRSF11B), regulation of gene transcription (SEC14L2, MSX2, TFAP2B, NRIP3) and metal ion binding (CYP4Z1, CYP4Z2P, SLC40A1, LTF, LIMCH1). CONCLUSION/SIGNIFICANCE: This new gene set should help to understand the behavior of PIK3CA-mutated cancers and detailed knowledge of Wnt signaling activation could lead to novel therapeutic strategies

Phosphatidylinositol 3-kinase pathway activation in breast cancer brain metastases

Activation status of the phosphatidylinositol 3-kinase (PI3K) pathway in breast cancer brain metastases (BCBMs) is largely unknown. We examined expression of phospho(p)-AKT, p-S6, and phosphatase and tensin homologue (PTEN) in BCBMs and their implications for overall survival (OS) and survival after BCBMs. Secondary analyses included PI3K pathway activation status and associations with time to distant recurrence (TTDR) and time to BCBMs. Similar analyses were also conducted among the subset of patients with triple-negative BCBMs. METHODS: p-AKT, p-S6, and PTEN expression was assessed with immunohistochemistry in 52 BCBMs and 12 matched primary BCs. Subtypes were defined as hormone receptor (HR)+/HER2-, HER2+, and triple-negative (TNBC). Survival analyses were performed by using a Cox model, and survival curves were estimated with the Kaplan-Meier method. RESULTS: Expression of p-AKT and p-S6 and lack of PTEN (PTEN-) was observed in 75%, 69%, and 25% of BCBMs. Concordance between primary BCs and matched BCBMs was 67% for p-AKT, 58% for p-S6, and 83% for PTEN. PTEN- was more common in TNBC compared with HR+/HER2- and HER2+. Expression of p-AKT, p-S6, and PTEN- was not associated with OS or survival after BCBMs (all, P > 0.06). Interestingly, among all patients, PTEN- correlated with shorter time to distant and brain recurrence. Among patients with TNBC, PTEN- in BCBMs was associated with poorer overall survival. CONCLUSIONS: The PI3K pathway is active in most BCBMs regardless of subtype. Inhibition of this pathway represents a promising therapeutic strategy for patients with BCBMs, a group of patients with poor prognosis and limited systemic therapeutic options. Although expression of the PI3K pathway did not correlate with OS and survival after BCBM, PTEN- association with time to recurrence and OS (among patients with TNBC) is worthy of further study

MYC Cooperates with AKT in Prostate Tumorigenesis and Alters Sensitivity to mTOR Inhibitors

MYC and phosphoinositide 3-kinase (PI3K)-pathway deregulation are common in human prostate cancer. Through examination of 194 human prostate tumors, we observed statistically significant co-occurrence of MYC amplification and PI3K-pathway alteration, raising the possibility that these two lesions cooperate in prostate cancer progression. To investigate this, we generated bigenic mice in which both activated human AKT1 and human MYC are expressed in the prostate (MPAKT/Hi-MYC model). In contrast to mice expressing AKT1 alone (MPAKT model) or MYC alone (Hi-MYC model), the bigenic phenotype demonstrates accelerated progression of mouse prostate intraepithelial neoplasia (mPIN) to microinvasive disease with disruption of basement membrane, significant stromal remodeling and infiltration of macrophages, B- and T-lymphocytes, similar to inflammation observed in human prostate tumors. In contrast to the reversibility of mPIN lesions in young MPAKT mice after treatment with mTOR inhibitors, Hi-MYC and bigenic MPAKT/Hi-MYC mice were resistant. Additionally, older MPAKT mice showed reduced sensitivity to mTOR inhibition, suggesting that additional genetic events may dampen mTOR dependence. Since increased MYC expression is an early feature of many human prostate cancers, these data have implications for treatment of human prostate cancers with PI3K-pathway alterations using mTOR inhibitors

PI3K inhibition results in enhanced HER signaling and acquired ERK dependency in HER2-overexpressing breast cancer

There is a strong rationale to therapeutically target the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway in breast cancer since it is highly deregulated in this disease and it also mediates resistance to anti-HER2 therapies. However, initial studies with rapalogs, allosteric inhibitors of mTORC1, have resulted in limited clinical efficacy probably due to the release of a negative regulatory feedback loop that triggers AKT and ERK signaling. Since activation of AKT occurs via PI3K, we decided to explore whether PI3K inhibitors prevent the activation of these compensatory pathways. Using HER2-overexpressing breast cancer cells as a model, we observed that PI3K inhibitors abolished AKT activation. However, PI3K inhibition resulted in a compensatory activation of the ERK signaling pathway. This enhanced ERK signaling occurred as a result of activation of HER family receptors as evidenced by induction of HER receptors dimerization and phosphorylation, increased expression of HER3 and binding of adaptor molecules to HER2 and HER3. The activation of ERK was prevented with either MEK inhibitors or anti-HER2 monoclonal antibodies and tyrosine kinase inhibitors. Combined administration of PI3K inhibitors with either HER2 or MEK inhibitors resulted in decreased proliferation, enhanced cell death and superior anti-tumor activity compared with single agent PI3K inhibitors. Our findings indicate that PI3K inhibition in HER2-overexpressing breast cancer activates a new compensatory pathway that results in ERK dependency. Combined anti-MEK or anti-HER2 therapy with PI3K inhibitors may be required in order to achieve optimal efficacy in HER2-overexpressing breast cancer. This approach warrants clinical evaluation

An integrative multi-dimensional genetic and epigenetic strategy to identify aberrant genes and pathways in cancer

<p>Abstract</p> <p>Background</p> <p>Genomics has substantially changed our approach to cancer research. Gene expression profiling, for example, has been utilized to delineate subtypes of cancer, and facilitated derivation of predictive and prognostic signatures. The emergence of technologies for the high resolution and genome-wide description of genetic and epigenetic features has enabled the identification of a multitude of causal DNA events in tumors. This has afforded the potential for large scale integration of genome and transcriptome data generated from a variety of technology platforms to acquire a better understanding of cancer.</p> <p>Results</p> <p>Here we show how multi-dimensional genomics data analysis would enable the deciphering of mechanisms that disrupt regulatory/signaling cascades and downstream effects. Since not all gene expression changes observed in a tumor are causal to cancer development, we demonstrate an approach based on multiple concerted disruption (MCD) analysis of genes that facilitates the rational deduction of aberrant genes and pathways, which otherwise would be overlooked in single genomic dimension investigations.</p> <p>Conclusions</p> <p>Notably, this is the first comprehensive study of breast cancer cells by parallel integrative genome wide analyses of DNA copy number, LOH, and DNA methylation status to interpret changes in gene expression pattern. Our findings demonstrate the power of a multi-dimensional approach to elucidate events which would escape conventional single dimensional analysis and as such, reduce the cohort sample size for cancer gene discovery.</p

An integrative genomic and proteomic analysis of PIK3CA, PTEN and AKT mutations in breast cancer

Phosphatidylinositol-3-kinase (PI3K)/AKT pathway aberrations are common in cancer. By applying mass spectroscopy-based sequencing and reverse phase protein arrays to 547 human breast cancers and 41 cell lines, we determined the subtype specificity and signaling effects of PIK3CA, AKT and PTEN mutations, and the effects of PIK3CA mutations on responsiveness to PI3K inhibition in-vitro and on outcome after adjuvant tamoxifen. PIK3CA mutations were more common in hormone receptor positive (33.8%) and HER2-positive (24.6%) than in basal-like tumors (8.3%). AKT1 (1.4%) and PTEN (2.3%) mutations were restricted to hormone receptor-positive cancers with PTEN protein levels also being significantly lower in hormone receptor-positive cancers. Unlike AKT1 mutations, PIK3CA (39%) and PTEN (20%) mutations were more common in cell lines than tumors, suggesting a selection for these but not AKT1 mutations during adaptation to culture. PIK3CA mutations did not have a significant impact on outcome in 166 hormone receptor-positive breast cancer patients after adjuvant tamoxifen. PIK3CA mutations, in comparison with PTEN loss and AKT1 mutations, were associated with significantly less and indeed inconsistent activation of AKT and of downstream PI3K/AKT signaling in tumors and cell lines, and PTEN loss and PIK3CA mutation were frequently concordant, suggesting different contributions to pathophysiology. PTEN loss but not PIK3CA mutations rendered cells sensitive to growth inhibition by the PI3K inhibitor LY294002. Thus, PI3K pathway aberrations likely play a distinct role in the pathogenesis of different breast cancer subtypes. The specific aberration may have implications for the selection of PI3K-targeted therapies in hormone receptor-positive breast cancer