Clear cell ovarian cancers with microsatellite instability: A unique subset of ovarian cancers with increased tumor-infiltrating lymphocytes and PD-1/PD-L1 expression.

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Clear cell ovarian cancers with microsatellite instability: A unique subset of ovarian cancers with increased tumor-infiltrating lymphocytes and PD-1/PD-L1 expression.

Oncoimmunology. 2017;6(2):e1277308

Authors: Howitt BE, Strickland KC, Sholl LM, Rodig S, Ritterhouse LL, Chowdhury D, D'Andrea AD, Matulonis UA, Konstantinopoulos PA

Abstract
Clear cell ovarian carcinoma (CCOC) represents a distinct histologic subtype of ovarian cancer associated with significantly worse prognosis across all stages and no effective therapeutic options. Here, we report a rare but clinically important cohort of CCOCs with microsatellite instability (MSI) (MSI-CCOCs), which are highly immunogenic and may thus be very responsive to immune checkpoint blockade. CCOCs with MSI exhibit a significantly higher number of CD8(+) TILs, higher CD8(+)/CD4(+) ratio, and higher PD-1(+) TILs compared with microsatellite stable (MSS) CCOCs and compared with high grade serous ovarian cancers, which are the most common histologic subtype of ovarian cancer. Of note, PD-L1 expression in tumor cells or immune cells was noted in all cases of CCOCs with MSI. These observations open an alternative therapeutic avenue for a fraction of patients with CCOC and argue for the routine testing of CCOCs for MSI, a test that is not currently routinely performed.

PMID: 28344892 [PubMed - in process]

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