Double PIK3CA mutations in cis increase oncogenicity and sensitivity to PI3K? inhibitors.
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ABSTRACT:
SUBMITTER: Vasan N
PROVIDER: S-EPMC7173400 | biostudies-literature | 2019 Nov
REPOSITORIES: biostudies-literature
Publications
Double <i>PIK3CA</i> mutations in cis increase oncogenicity and sensitivity to PI3Kα inhibitors.
Vasan Neil N Razavi Pedram P Johnson Jared L JL Shao Hong H Shah Hardik H Antoine Alesia A Ladewig Erik E Gorelick Alexander A Lin Ting-Yu TY Toska Eneda E Xu Guotai G Kazmi Abiha A Chang Matthew T MT Taylor Barry S BS Dickler Maura N MN Jhaveri Komal K Chandarlapaty Sarat S Rabadan Raul R Reznik Ed E Smith Melissa L ML Sebra Robert R Schimmoller Frauke F Wilson Timothy R TR Friedman Lori S LS Cantley Lewis C LC Scaltriti Maurizio M Baselga José J
Science (New York, N.Y.) 20191101 6466
Activating mutations in <i>PIK3CA</i> are frequent in human breast cancer, and phosphoinositide 3-kinase alpha (PI3Kα) inhibitors have been approved for therapy. To characterize determinants of sensitivity to these agents, we analyzed <i>PIK3CA</i>-mutant cancer genomes and observed the presence of multiple <i>PIK3CA</i> mutations in 12 to 15% of breast cancers and other tumor types, most of which (95%) are double mutations. Double <i>PIK3CA</i> mutations are in cis on the same allele and result ...[more]
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Project description:INTRODUCTION:Triple negative breast cancer (TNBC) is a heterogeneous collection of biologically diverse cancers, which contributes to variable clinical outcomes. Previously, we identified a TNBC subtype that has a luminal phenotype and expresses the androgen receptor (AR+). TNBC cells derived from these luminal AR + tumors have high frequency phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutations. The purpose of this study was to determine if targeting phosphoinositide 3-kinase (PI3K) alone or in combination with an AR antagonist is effective in AR + TNBC. METHODS:We determined the frequency of activating PIK3CA mutations in AR + and AR- TNBC clinical cases. Using AR?+?TNBC cell line and xenograft models we evaluated the effectiveness of PI3K inhibitors, used alone or in combination with an AR antagonist, on tumor cell growth and viability. RESULTS:PIK3CA kinase mutations were highly clonal, more frequent in AR + vs. AR- TNBC (40% vs. 4%), and often associated with concurrent amplification of the PIK3CA locus. PI3K/mTOR inhibitors had an additive growth inhibitory effect when combined with genetic or pharmacological AR targeting in AR + TNBC cells. We also analyzed the combination of bicalutamide +/- the pan-PI3K inhibitor GDC-0941 or the dual PI3K/mTOR inhibitor GDC-0980 in xenograft tumor studies and observed additive effects. CONCLUSIONS:While approximately one third of TNBC patients respond to neoadjuvant/adjuvant chemotherapy, recent studies have shown that patients with AR + TNBC are far less likely to benefit from the current standard of care chemotherapy regimens and novel targeted approaches need to be investigated. In this study, we show that activating PIK3CA mutations are enriched in AR?+?TNBC; and, we show that the growth and viability of AR + TNBC cell line models is significantly reduced after treatment with PI3K inhibitors used in combination with an AR antagonist. These results provide rationale for pre-selection of TNBC patients with a biomarker (AR expression) to investigate the use of AR antagonists in combination with PI3K/mTOR inhibitors.
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| S-EPMC3072168 | biostudies-literature
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Project description:OBJECTIVE:Recent sequencing studies of head and neck squamous cell carcinomas (HNSCCs) have identified the phosphatidylinositol 3-kinase (PI3K) pathway as the most frequently mutated, oncogenic pathway in this cancer type. Despite the frequency of activating genomic alterations in PIK3CA (the gene encoding the catalytic subunit of PI3K, targeted inhibitors of PI3K have not shown clinical efficacy as monotherapies. We hypothesized that co-dependent pathways, including the Ras-MEK-ERK pathway, may still be functional in the presence of PI3K inhibitors and might serve as mediators of this resistance. METHODS:We assessed the hypothesis using resazurin cell viability and trypan blue exclusion assays. We also used Western blot to characterize Ras-MEK-ERK pathway activity. STUDY DESIGN:We evaluated this hypothesis in six PIK3CA-amplified, PI3K inhibitor-resistant HNSCC cell lines following treatment with pan and alpha-isoform selective PI3K inhibitors (BKM120 and HS-173 respectively). We also tested the effect of combination treatment with PI3K inhibitor HS-173 and MEK inhibitor trametinib or EGFR inhibitor gefitinib. RESULTS:Our results displayed maintenance of Ras-MEK-ERK pathway activity in 4 of 6 HNSCC cell lines after PI3K inhibitor treatment. We also found that UM-SCC-69 and UM-SCC-108 cells display synergistic responses to dual therapy. CONCLUSION:This study suggests that inhibition of the PI3K and Ras-MEK-ERK pathways might be effective in some HNSCC patients; however, it also prompts the study of additional resistance mechanisms to identify synergistic combination therapies for tumors resistant to these di-therapies.
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Project description:Therapeutic targeting of the PI3K pathway is an active area of research in multiple cancer types, including breast and endometrial cancers. This pathway is commonly altered in cancer and plays an integral role in numerous vital cellular functions. Mutations in the PIK3CA gene, resulting in a constitutively active form of PI3K, often occur in colorectal cancer, though the population of patients who would benefit from targeting this pathway has yet to be identified. In human colorectal cancers, PIK3CA mutations most commonly occur concomitantly with loss of adenomatous polyposis coli (APC). Here, treatment strategies are investigated that target the PI3K pathway in colon cancers with mutations in APC and PIK3CA Colorectal cancer spheroids with Apc and Pik3ca mutations were generated and characterized confirming that these cultures represent the tumors from which they were derived. Pan and alpha isomer-specific PI3K inhibitors did not induce a significant treatment response, whereas the dual PI3K/mTOR inhibitors BEZ235 and LY3023414 induced a dramatic treatment response through decreased cellular proliferation and increased differentiation. The significant treatment responses were confirmed in mice with Apc and Pik3ca-mutant colon cancers as measured using endoscopy with a reduction in median lumen occlusion of 53% with BEZ235 and a 24% reduction with LY3023414 compared with an increase of 53% in controls (P < 0.001 and P = 0.03, respectively). This response was also confirmed with 18F-FDG microPET/CT imaging.Implications: Spheroid models and transgenic mice suggest that dual PI3K/mTOR inhibition is a potential treatment strategy for APC and PIK3CA-mutant colorectal cancers. Thus, further clinical studies of dual PI3K/mTOR inhibitors are warranted in colorectal cancers with these mutations. Mol Cancer Res; 15(3); 1-11. ©2016 AACR.
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