Targeting replication stress to engage DNA sensing STING pathway derived anti-tumor immunity to improve the therapeutic outcomes in uterine cancer

Project Summary Microsatellite stable (MSS)/mismatch repair proficient (MMRP) uterine cancers (UCs) represent approximately two thirds (66%) of all UCs in The Cancer Genome Atlas (TCGA). The combination of pembrolizumab with lenvatinib is currently the only FDA approved treatment for recurrent MSS/MMRP UCs, but adverse effects are a major challenge in the clinic and a large population of patients do not respond to this regimen. There are currently no FDA approved and no effective salvage therapies for patients with recurrent MSS/MMRP UC who do not tolerate, do not respond or progress through pembrolizumab/lenvatinib. Notably, MSS/MMRP UCs are characterized by genomic alterations associated with high degree of replication stress (RS); therefore, use of DNA damage checkpoint kinase inhibitors such as WEE1 or ATR inhibitor can be therapeutically exploited to induce tumor-selective synthetic lethality and modulate anti-tumor immunity, representing an appealing strategy against these tumors. Furthermore, in our preliminary work, we have demonstrated that targeting the RS with ATR or WEE1 in UCs leads to activation of the STING/TBK1/IRF3 pathway. Thus, we hypothesize that DNA damage checkpoint kinase inhibitors will increase RS-associated DNA damage to engage DNA sensing STING pathway activation to prime the immunologically “cold” MSS/MMRP UCs into “hot” tumors; combined DNA damage targeting agents with immune checkpoint inhibitors (ICIs) can overcome tumor-associated immunosuppression and lead to effective antitumor activity against MSS/MMRP UCs. We propose to test an entirely novel strategy to extend the benefit of immunotherapy in MSS/MMRP UC by using DNA damage checkpoint kinase inhibitors in combination with ICIs in both human and murine models of UC. In Aim 1, we propose to characterize the immune effects of ATR and WEE1 inhibitors on human UC cell lines, patient-derived organoid models and tumor specimens from the clinical trials of adavosertib and BAY1895344/copanlisib from Projects 1 and 2 respectively. In Aim 2, we will assess the contribution of RS-targeting potentiated DNA sensing STING pathway activation to the immune effect and therapeutic efficacy of WEE1 or ATR inhibition in vivo in syngeneic models of UC, and in Aim 3, we will evaluate the anti-tumor immunity and therapeutic efficacy of WEE1i or ATRi in combination with ICI in vivo in syngeneic models of UC. The overarching goal of this project is to provide the mechanistic insights and important information to support initiation of clinical trials of effective combinations DNA damage checkpoint inhibitors with ICI in patients with MSS/MMRP UC.