Abstract LB115: Strong antitumor effect elicited by inhibition of AKT or FOXP3 in combination with anti-PD-L1 in Pten mutant lung squamous cell carcinoma

Abstract PTEN is mutated in ~10% lung squamous cell carcinoma (LUSC) patients, which results in hyperactivation of PI3K-AKT-mTOR signaling pathways. Mutations in the PI3K-AKT-mTOR pathway influence the configuration the tumor microenvironment (TME). We have recently reported that PTEN mutations in LUSC are associated with increased tumor infiltration of T regulatory immunosuppressive cells (Tregs) and fibrogenesis (PMID: 37311042). Moreover, we have demonstrated that PTEN mutations in LUSC induces resistance to anti-PD-1 therapy. Based on these findings, we have investigated whether blockade of AKT signaling with capivasertib (AZD5363) and/or inhibition of Treg-associated FOXP3 transcription factor, using the FOXP3 targeting antisense oligonucleotide (ASO) AZD8701 (FOXP3i), would cause tumor growth inhibition in the PTEN mutant context. In in vitro assays we found that Pten-null LUSC UN680 murine cells were highly sensitive to capivasertib, with inhibition of the AKT-mediated signaling cascade, reduction in cyclin D1 levels, cytoplasmic translocation of FOXO1 and increase in apoptosis and autophagy. In in vivo studies using Pten-null UN680 cells subcutaneously injected in AJ immunocompetent mice, treatment with either capivasertib or the FOXP3i induced >90% tumor regression and increased survival. Moreover, on average 3/8 (~37%) animals were cured in each treatment group. In a re-challenge experiment performed in animals cured by the FOXP3i, tumors were not developed upon injection of Pten-null UN680 cells, demonstrating immunological memory. Combination of capivasertib+FOXP3i at the same doses did not cause further tumor growth inhibition, but combination of capivasertib+anti-PD-L1 or FOXP3i+anti-PD-L1 increased antitumor benefit compared to monotherapy treatment, and further increased survival. In summary, we demonstrate that immunotherapy resistant tumors with hyperactivation of AKT due to Pten mutation are highly sensitive to AKT or FOXP3 inhibition and that combinatorial strategies using these targets and anti-PD-L1 can be appropriate strategies to treat these tumors. Citation Format: Maeva Houry, Miriam Redrado, Larissa Carnevalli, Simon Barry, Nuria Galan, Nerea Otegui, Sergio Leon, Luis Montuenga, Francisco Exposito, Alfonso Calvo. Strong antitumor effect elicited by inhibition of AKT or FOXP3 in combination with anti-PD-L1 in Pten mutant lung squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB115.