Tissue-specific signatures of activating PIK3CA and RAS mutations in carcinosarcomas of gynecologic origin.

OBJECTIVES: Gynecologic carcinosarcoma is an aggressive malignancy that requires more effective treatment approaches. However, therapeutic implications regarding the specific gynecologic site of origin and the admixture of carcinomatous and sarcomatous elements that define this tumor remain uncertain. Therefore, broad genotyping was performed to identify tissue-specific somatic mutational profiles that may help direct targeted therapies in this complex neoplasia. METHODS: Genotyping was conducted on primary gynecologic carcinosarcomas arising from various disease sites (uterus, ovary, fallopian tube, vagina) and within isolated histological subcomponents. Nucleic acids extracted from diagnostic tissue were used in a genotyping platform that simultaneously queried >120 common mutations across 14 cancer genes. Mutational status was correlated with clinical variables using logistic regression and Kaplan-Meier survival estimates. RESULTS: Cancer gene mutations were identified in 46% of the 52 patient cohort and include TP53 (23%), PIK3CA (19%), KRAS (15%), CTNNB1 (4%) and NRAS (2%). Mutation in a single gene was observed in 31% of patient samples, while synchronous mutations involving 2 and 3 genes were noted in 13% and 2% of samples, respectively. Comparative evaluation of the carcinomatous and sarcomatous elements within a tumor demonstrated a similar mutation signature. Mutations in PIK3CA, KRAS and NRAS were exclusive to tumors of uterine origin and age-adjusted Cox proportional hazards modeling associated advanced age, stage and TP53 mutations with decreased survival in the uterine subset. CONCLUSION: While carcinosarcomas across gynecologic disease sites are histologically similar, therapeutically relevant mutations in the mitogen-activated protein kinase and phosphatidylinositol 3-kinase pathways predominated in carcinosarcomas arising in the uterus.

Detection of novel actionable genetic changes in salivary duct carcinoma helps direct patient treatment.

PURPOSE: Salivary duct carcinomas (SDC) are a rare and aggressive subtype of salivary gland cancers for which cytotoxic chemotherapy has limited efficacy. We investigated whether genotyping analysis could detect novel tumor-specific mutations that would help direct SDC patient treatment using targeted agents. EXPERIMENTAL DESIGN: We genotyped 27 SDC archival specimens from patients followed at Massachusetts General Hospital and Massachusetts Eye and Ear Infirmary (Boston, MA) between 2000 and 2011. These included the tumors of 8 patients who were tested prospectively. Targeted mutational analysis of 13 clinically relevant cancer genes was conducted using SNaPshot multiplexed genotyping. FISH was conducted to detect HER2 gene amplification. Patient medical records and tumor histopathologic features were retrospectively reviewed. RESULTS: Mutually exclusive genetic aberrations were detected in 15 of 27 (56%) tumors, including 2 (7%) mutations in BRAF, 5 (19%) mutations in PIK3CA, and 8 (30%) cases of HER2 gene amplification. To our knowledge, this is the first time that BRAF and PIK3CA mutations have been reported in this tumor type. Prospective clinical testing of 8 patients with SDC identified actionable genetic alterations in 6 tumors and influenced therapeutic decisions for all 6 patients. CONCLUSION: SNaPshot molecular profiling identified novel genetic changes in SDCs, expanded the therapeutic options for patients with this rare tumor, and is changing SDC management at our institution. These findings highlight the importance of using broad-based genetic profiling to expedite the identification of effective-targeted therapies for patients with rare malignancies.

Activation of PI3K signaling in Merkel cell carcinoma.

PURPOSE: Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine tumor, often metastatic at presentation, for which current chemotherapeutic regimens are largely ineffective. As its pathogenesis is still unknown, we hypothesized that deregulation of signaling pathways commonly activated in cancer may contribute to MCC tumorigenesis and may provide insights into targeted therapy approaches for this malignancy. EXPERIMENTAL DESIGN: We retrospectively profiled 60 primary MCC samples using a SNaPshot-based tumor genotyping assay to screen for common mutations in 13 cancer genes. RESULTS: We identified mutations in 9 (15%) MCC primary tumors, including mutations in TP53 (3 of 60) and activating mutations in the PIK3CA gene (6 of 60). Sanger sequencing of the primary MCC tumors detected one additional PIK3CA mutation (R19K) that had not been previously described in cancer. Merkel cell polyoma virus (MCPyV) was detected in 38 (66%) MCC cases and patients with MCPyV-positive cancers showed a trend toward better survival. With one exception, the presence of MCPyV and activating mutations in PIK3CA appeared mutually exclusive. We observed that signaling through the PI3K/pAKT pathway was active in one MCPyV-positive and in all MCPyV-negative MCC cell lines, as evidenced by AKT phosphorylation. Importantly, the presence of a PIK3CA-activating mutation was associated with sensitivity to treatment with ZST474, a specific phosphoinositide 3-kinase (PI3K) inhibitor, and to NVP-BEZ235, a dual PI3K/mTOR inhibitor, targeted agents under active clinical development. CONCLUSIONS: PI3K pathway activation may drive tumorigenesis in a subset of MCC and screening these tumors for PIK3CA mutations could help identify patients who may respond to treatment with PI3K pathway inhibitors.