Abstract 3315: Activating innate immune response as strategy for endometrial cancer treatment
Authors: Morelli Maria Pia , Fanitni Massimo , Diggs Alexandra , Tsang Kwong Yok , Arlen Philip , Annunziata Christina 
Published: September 2020

Abstract
Background: Uterine cancer is the 6th most common cause of death for women in the USA, and about 10,000 women will die from this disease every year. A better understanding of the disease biology has opened the door for more individualized treatment approaches. In the present study we focused on new strategies to potentiate the innate immune response against endometrial cancer. To direct NK cell activity, we used the monoclonal antibody NEO-201, which targets a tumor specific variant of CEACAM-5 and -6, in combination with human recombinant IL-15. NEO-201 is a humanized monoclonal antibody developed through vaccine, and is currently being evaluated in a first-in-human Phase I study currently ongoing at the NCI (NCT03476681). This antibody exerts anti-tumor activity via NK-mediated ADCC. We hypothesized that the expression of tumor associated antigen for NEO-201 correlates with specific tumor biological characteristics, with a goal of designing new rational combinations to potentiate the anti-tumor immune response.
Method: To establish the biological relevance of this antigen, we screened a Tissue Microarray (TMA) of endometrial cancer patient tissues by IHC. To identify relevant cell line models, we screened 11 endometrial cancer cell lines for the expression of the antigen recognized by NEO-201 by IHC, WB and FACS and studied the biological characteristics of the same cell lines by whole exome and RNA sequencing. Next, we evaluated NEO-201 anti-tumor activity in combination with IL-15 using ADCC assay in vitro.
Result: The expression of the antigen recognized by NEO-201 was confirmed in the patient TMA, where the antigen was detected predominantly on cells membrane and apical surface in 10% of samples. ACI-158 cell line was strongly positive for NEO-201 antigen by WB, FACS and IHC. To evaluate ADCC, NK were isolated from healthy donor PBMCs and incubated with IL15 for 48hours, before performing a chromium release assay. The stimulation with IL-15 increased NK mediated ADCC by 2.5 fold, regardless of the donor genotype. Addition of NEO-201 to facilitate NK mediated ADCC further increased activation by 1.5 to 6 fold. Preliminary sequencing data showed that 5 cell lines express MMR gene mutations, 3 NRAS/KRAS/ERK1-2 mutations, 1 AKT and 1 CTNNB1 mutation, and 2 cell lines carry HER2+ amplification.
Conclusion: NEO-201 in combination with IL15 showed promising results in activating NK cells against endometrial cancer cells in vitro. Additional in vitro and in vivo studies are ongoing to optimize the combination and to correlate its activity with cells' biological characteristics.
Citation Format: Maria Pia Morelli, Massimo Fanitni, Alexandra Diggs, Kwong Yok Tsang, Philip Arlen, Christina Annunziata. Activating innate immune response as strategy for endometrial cancer treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3315.