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Poster by Neha Gopinath (Sidra Medicine), Ishita Gupta (Sidra Medicine), Alice Turdo (Sidra Medicine), Rebecca Mathew (Sidra Medicine), Harshitha Shobha Manjunath (Sidra Medicine), Mohammed Toufiq (Sidra Medicine), Ola Hussein (Sidra Medicine), Evonne Chin-Smith (Sidra Medicine), Matilde Todaro (Sidra Medicine), Giorgio Stassi (University of Palermo), Sara Tomei (Sidra Medicine), Ira Skvortsova (Medical University of Innsbruck and Tyrolean Cancer Research Institute), Soldano Ferrone (Harvard Medical School), Cristina Maccalli (Sidra Medicine) Background: Cancer stem cells (CSCs) represent a rare subpopulation of cells within the tumor that are considered responsible of metastatization and resistance to therapies, including immunotherapy. Objective: The aim of this study is to identify the molecular mechanisms regulating the immunological properties of cancer stem cells (CSCs) isolated from colorectal cancer (CRC) and breast cancer (BC) using integrative approaches including flow cytometry, miRNAs and RNA seq-based transcriptomic profile and in vitro functional assays. Methods: Colorectal cancer (CRC; N=15) and breast cancer (BC; N=21) cell lines, including differentiated tumor cells and CSCs, and, for BC, selected in vitro for radioresistance or invasiveness were used for this study. The baseline expression of HLA molecules and the components involved in the antigen processing machinery (APM) following or not the treatment with immunomodulatory or epigenetic agents was assessed through flow cytometry. Tumor cells were co-cultured with HLA-matched peripheral blood mononuclear cells (PBMCs) isolated from healthy donors to assess the efficiency of the CRC and BC cells endowed with stemness properties to elicit antigen-specific T cell responses. The nCounter platform (Nanostring) was utilized to assess the hybridization with 800 probes for miRNAs and the RNA seq-based transcriptomic profile (Lexogen) was also assessed. Results: A general impairment of the expression of HLA and APM molecules was observed in CRC and BC lines. The down-modulation of the expression of HLA and APM was superior in “stem-like” cells as compared to the differentiated tumor cells. The treatment of these cells with immunomodulating or epigenetic agents could only partially restore the expression of these molecules. The induction in vitro of anti-tumor T cell responses through the co-culture of tumor cells with PBMCs, was associated with the levels of the expression HLA and APM molecules by the tumor cells and on the efficiency of their up-modulation by either immunomodulating or epigenetic agents. Differential miRNA profiles (p

A number of prostate cancer (PCa)-specific genomic aberrations (denominated BRCAness genes) have been discovered implicating sensitivity to PARP inhibition within the concept of synthetic lethality. Recent clinical studies show favorable results for the PARP inhibitor olaparib used as single agent for treatment of metastatic castration-resistant PCa. Using 2D and 3D cell culture models mimicking the different treatment and progression stages of PCa, we evaluated a potential use for olaparib in combination with first-line endocrine treatments, androgen deprivation, and complete androgen blockade, and as a maintenance therapy following on from endocrine therapy. We demonstrate that the LNCaP cell line, possessing multiple aberrations in BRCAness genes, is sensitive to olaparib. Additive effects of olaparib combined with endocrine treatments in LNCaP are noted. In contrast, we find that the TMPRSS2:ERG fusion-positive cell lines VCaP and DuCaP do not show signs of synthetic lethality, but are sensitive to cytotoxic effects caused by olaparib. In consequence, additive effects of olaparib with endocrine therapy were not observable in these cell lines, showing the need for synthetic lethality in combination treatment regimens. Additionally, we show that PCa cells remain sensitive to olaparib treatment after initial androgen deprivation implicating a possible use of olaparib as maintenance therapy. In sum, our preclinical data recommend olaparib as a synthetic lethal treatment option in combination or sequenced to first-line endocrine therapy for PCa patients with diagnosed BRCAness.

Objective Epithelial-mesenchymal crosstalk (EMC) contributes to tumor progression, chemoresistance and acquisition of a mesenchymal phenotype (EMT) of cancer cells. This study aims to investigate the effects of EMC on radioresistance in head and neck squamous cell carcinoma (HNSCC) cells. Methods In tumor cell lines, the response of HNSCC cells, stimulated with EMC conditioned medium (CM), to irradiation was evaluated with viability and clonogenic assays. Dose modifying factors (DMF) were calculated from the results of clonogenic assays. Potential pathways involved in radioresistance were analyzed with quantitative Real-Time PCR and western blot. Results CM significantly reduced the doubling time of SCC-25 cells (from 32.8 hours to 16.8 hours, p=0.0001) and Detroit 562 cells (from 88.5 hours to 29.6 hours, p=0.014). Further it increased clonogenic survival after irradiation. The DMF of CM was 2.04 ± 0.43 (mean ± standard deviation) for SCC-25 cells (p=0.015) and 2.14 ± 0.34 for Detroit 562 cells (p=0.008). Treatment with CM more than tripled the ERCC1 and survivin gene expression in SCC-25 cells. Conclusion EMC induced pathways involved in cell survival and DNA repair and led to increased radioresistance in HNSCC cells.