Background: The major histocompatibility complex class I polypeptide-related sequence A (MICA) is one of the ligands of the natural killer group 2D (NKG2D) activating receptor. MICA stimulates NKG2D, which further triggers activation of natural killer cells and leads to killing of infected target cells. To subvert the biological function of NKG2D, tumor cells utilize an escape strategy by shedding overexpressed MICA. In this study, we determined the levels of MICA in colorectal cancers (CRCs). Additionally, we established correlations between MICA expression and clinical characteristics. Publicly available data and bioinformatics tools were used for validation purposes. Methods: We determined the MICA RNA expression levels and assessed their correlation with clinicopathological parameters in CRC using the UALCAN web-portal. We performed immunohistochemical analysis on tissue microarrays having 192 samples, acquired from 96 CRC patients, to validate the expression of MICA in CRC and adjacent uninvolved tissue and investigated its prognostic significance by Kaplan-Meier and proportional hazards methods. Results: Bioinformatics and immunohistochemical analyses showed that MICA expression was significantly upregulated in CRCs as compared to uninvolved tissue, and the overexpression of MICA was independent of pathologic stage, histotype, nodal metastasis status, p53-status, as well as patient’s race, age and gender. Moreover, PROGgeneV2 survival analysis of two cohorts showed a poor prognosis for CRC patients exhibiting high MICA expression. Conclusions: Overall, our findings for CRC patients demonstrate generally high expression of MICA, and suggest that a poor prognosis relates to high MICA expression. These results can be further explored due to their potential to provide clues to the contribution of the tumor microenvironment to the progression of CRC.

Breast cancer (BC) is one of the deadliest cancers in women. Among various subtypes, triple-negative breast cancer (TNBC) is the most aggressive and hard to treat subtype of breast cancer because it is highly metastatic and lacks targeted therapies. The death rate from BC is higher among African American (AA) women than among women of other races and ethnicities. The higher incidences of TNBCs and their aggressive growth in young AA women contributing to higher death rates indicate a biological basis for this difference. Thus, it is imperative to understand the molecular mechanisms that contribute to aggressive tumor growth in AA women, identify biomarkers to select patients who will respond to existing therapies, and develop effective therapeutics to reduce this disparity. Our previous findings showed that the DNA repair protein, RAD51, is overexpressed in AA TNBC patients and correlates with a poor prognosis relative to European American (EA) TNBC patients. However, the exact mechanism behind the regulation of RAD51 has not been identified. Our miRNA seq analysis shows a list of downregulated miRNAs in AA TNBC cell lines compared to EA TNBC cell lines. Interestingly, the miRDB-MicroRNA Target Prediction Database predicted that miR-214-5P has the seed sequence to bind and degrade RAD51 mRNA. Analysis of the TCGA database by UALCAN portal also shows a decreased expression of miR-214-5P in AA TNBC patients compared to EA TNBC patients. Treating the AA TNBC cell lines with miR-214-5P mimic downregulates RAD51 expression in a cell cycle-independent manner and also induces HR-deficiency as measured by Dr-GFP assay. Based on these results, we designed a synergistic lethality-based combination of miR-214-5P and Olaparib in TNBC cells. Data from our preclinical evaluations show miR-214-5P and Olaparib cause increased DNA strand breaks, and synergistic TNBC cell lethality compared to individual treatments. Together, our data indicate that miR-214-5P regulates RAD51 and either of these genes could be biomarkers for aggressive TNBC and racial disparity in BC therapeutic outcomes. Citation Format: Ganesh Acharya, Chinnadurai Mani, Upender Manne, Komaraiah Palle. miRNA-214-5P regulates RAD51, a biomarker for aggressive disease and racial disparities in triple-negative breast cancer [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr C027.

Socioeconomic status and health disparities are a significant liability for the prevalence of many diseases, including cancer. Among many contributing factors, lack of socioeconomic advancement and inequality in resource distribution is closely associated with prostate cancer occurrence. The State of Alabama has one of the highest rates of prostate cancer in the nation and the third cancer epidemic at the state level. Due to widespread disparities in infrastructure development, political willpower, equal healthcare, and education opportunity, Alabama's Black Belt region has been further divided by socioeconomic statuses among the majority (Whites) and minority (African American) populations. The purpose of this research is to recognize Alabama's health burdens and socioeconomic status using geo-spatial technology (GIS) to examine prostate cancer health disparity. GIS has become a valuable decision-making tool in understanding the public health care sectors, including prostate cancer prevalence. GIS supports assembling spatial and non-spatial data, displays the spatial distribution of health disparities, and underlines further interconnectivity of policy-related questions. This research incorporates county-level prostate cancer data using GIS and outlining the correlation between prostate cancer prevalence and socioeconomic factors to understand Alabama's cancer health disparity and equity. A combination of socioeconomic factors and state and federal-level cancer epidemic data sources underline Alabama's black belt region (predominantly African American) prostate cancer prevalence is higher than the non-black belt. The GIS analysis demonstrated that effective cancer prevention programs are needed to eliminate health disparities and enhance health equity among underserved populations of Alabama. Citation Format: Ram Alagan, Seela Aladuwaka, Rajesh Singh, Upender Manne, Manoj K. Mishra. Implementing geospatial technology to understand the prostate cancer health burdens and socioeconomic status in Alabama [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3687.

3625 Background: In colorectal cancer (CRC) and endometrial cancer (EC) patients (pts), preliminary data suggest a differential response to immune checkpoint inhibitors (ICIs) according to different MMR alterations. The drivers of this difference remain unknown and no reliable predictive biomarker has been found. We explored the genomic alterations, tumor mutation burden (TMB), immune-related gene expressions and signatures, tumor microenvironment (TME), neoantigen load and median overall survival (mOS) inCRC and EC pts treated with ICIs with different MMR alterations. Methods: 13,701 CRC and 3,315 EC specimens were tested at Caris Life Sciences (Phoenix, AZ) with Next Gen Sequencing (NGS) of DNA (592-gene or whole exome) and RNA (whole transcriptome). MMR/MSI status was determined by IHC of MMR protein and/or NGS. Immune cell abundance was quantified using quanTIseq. Gene expression profiles were analyzed for T cell-inflamed signature (TIS) and IFN-gamma scores. Immune epitope prediction was performed using the NetMHCpan v4.0 method in the Immune Epitope Database. Real-world mOS was obtained from insurance claims data and calculated from tissue collection or ICIs start to last contact. Statistical significance was determined using chi-square/Fisher-Exact and adjusted for multiple comparisons (adjusted p < 0.05). Results: In CRC, 84 (0.6%) pts had intact expression of MLH1 and PMS2 and co-loss of MSH2 and MSH6 (MutS) and 648 (4.7%) had co-loss of MLH1 and PMS2 and intact MSH2 and MSH6 (MutL). 117 (0.9%) had other MMR IHC loss. APC, KRAS, ERBB2, ERBB3 and MSH2 mutations rates were higher in MutS while BRAF mutation rate was higher in MutL. B cell, NK cell content and neoantigen load (high affinity epitopes: p < 0.05, intermediate: p < 0.01, low: p < 0.001) were higher in MutS. The mOS in MutS (N = 149) vs. MutL (N = 980) was 56 months (m) vs. 36 m (p = 0.003). In ICI-treated pts, the mOS in MutS (N = 28) vs. MutL (N = 149) was not reached (NR) vs. 32 m (p = 0.005). BRAF mutation didn’t impact survival in MutL. In EC, 48 (1.4%) pts had MutS and 915 (27.6%) had MutL. 81 (2.4%) had other MMR IHC loss. IHC-PD-L1, TMB, neoantigen load (high affinity epitopes: p < 0.01, intermediate: p < 0.0001, low: p < 0.0001), TIS, IFN-gamma scores, immune related gene expressions, TME (Macrophage M1, CD8+) were higher in MutS. The mOS in MutS (N = 94) vs. MutL (N = 1804) was NR vs. 47 m (p < 0.001). In ICI-treated pts, the mOS in MutS (N = 11) vs. MutL (N = 273) was NR vs. NR (p = 0.559). Conclusions: This is the largest study to explore differential response to ICIs in CRC and EC pts with different MMR alterations. In pts with CRC and EC, the mOS was longer in MutS compared to MutL. In ICI-treated pts, the mOS was longer in MutS compared to MutL in CRC but not in EC. Among the explored biomarkers, neoantigen load was higher in MutS compared to MutL in both CRC and EC and maybe the driving factor for differential response to ICIs.

Regulatory T (Treg) cells act as terminators of T cell immune response during prostate cancer progression and development. However, their role and immunosuppressive mechanism(s) in context to programmed death 1 (PD-1) is not completely understood. The present investigation is aimed to determine the role of PD-1 on Treg cells and their impact on CD8+ T cell function in prostatic tumor microenvironment using transgenic adenocarcinoma of the mouse prostate (TRAMP) cells (TRAMP C1, C2 and C3) as a model system. To execute the above aim, tumor induction studies were performed. Briefly, the C57BL/6 mice were administered with serial log concentrations of TRAMP (C1-3) cells. Interestingly, the TRAMP-C3 cells do not form tumor, however, TRAMP-C1 and TRAMP-C2 cells do form tumor. After tumor development, mice were sacrificed by cervical dislocation; tumor, lung, spleen, and draining lymph nodes were harvested when the tumor size reached approximately 20mm. Single cell suspensions were prepared from different organs, cells were then stained with specific antibodies, and flow analyzed for the expression of different immune markers. Our preliminary findings demonstrated that PD-1 expression on Foxp3+ Treg cells displayed greater suppressive capacity against CD8+ T cell function in tumor, lung, spleen, and draining lymph node when compared to the control. More importantly, Foxp3+ Treg(high) PD-1(high) interaction with PDL-1 induced immunosuppression by blocking CD8+ T cells function in prostatic tumor microenvironment. In conclusion, Foxp3+ Treg(high), PD-1(high), and CD8+(low) T cells may enhance tumor progression; thus, targeting the PD-1 on Treg cells may be a possible therapy to treat prostate cancer.