Immunotherapy resistance in non–small cell lung cancer (NSCLC) may be mediated by an immunosuppressive microenvironment, which can be shaped by the mutational landscape of the tumor. Here, we observed genetic alterations in the PTEN/PI3K/AKT/mTOR pathway and/or loss of PTEN expression in >25% of patients with NSCLC, with higher frequency in lung squamous carcinomas (LUSC). Patients with PTEN-low tumors had higher levels of PD-L1 and PD-L2 and showed worse progression-free survival when treated with immunotherapy. Development of a Pten-null LUSC mouse model revealed that tumors with PTEN loss were refractory to antiprogrammed cell death protein 1 (anti–PD-1), highly metastatic and fibrotic, and secreted TGFβ/CXCL10 to promote conversion of CD4+ lymphocytes into regulatory T cells (Treg). Human and mouse PTEN-low tumors were enriched in Tregs and expressed higher levels of immunosuppressive genes. Importantly, treatment of mice bearing Pten-null tumors with TLR agonists and anti-TGFβ antibody aimed to alter this immunosuppressive microenvironment and led to tumor rejection and immunologic memory in 100% of mice. These results demonstrate that lack of PTEN causes immunotherapy resistance in LUSCs by establishing an immunosuppressive tumor microenvironment that can be reversed therapeutically. Significance: PTEN loss leads to the development of an immunosuppressive microenvironment in lung cancer that confers resistance to anti–PD-1 therapy, which can be overcome by targeting PTEN loss–mediated immunosuppression.

Despite the great clinical success of immunotherapy in lung cancer patients, only a small percentage of them (<40%) will benefit from this therapy alone or combined with other strategies. Cancer cell-intrinsic and cell-extrinsic mechanisms have been associated with a lack of response to immunotherapy. The present study is focused on cancer cell-intrinsic genetic, epigenetic, transcriptomic and metabolic alterations that reshape the tumor microenvironment (TME) and determine response or refractoriness to immune checkpoint inhibitors (ICIs). Mutations in KRAS, SKT11(LKB1), KEAP1 and TP53 and co-mutations of these genes are the main determinants of ICI response in non-small-cell lung cancer (NSCLC) patients. Recent insights into metabolic changes in cancer cells that impose restrictions on cytotoxic T cells and the efficacy of ICIs indicate that targeting such metabolic restrictions may favor therapeutic responses. Other emerging pathways for therapeutic interventions include epigenetic modulators and DNA damage repair (DDR) pathways, especially in small-cell lung cancer (SCLC). Therefore, the many potential pathways for enhancing the effect of ICIs suggest that, in a few years, we will have much more personalized medicine for lung cancer patients treated with immunotherapy. Such strategies could include vaccines and chimeric antigen receptor (CAR) cells.

Effective strategies to reinvigorate the immune system are needed to improve outcomes in small cell lung cancer (SCLC). Targeting Src family kinases with dasatinib (Dasa) can elicit immunomodulatory effects in some cancer types. Here, we explored the potential of combining Dasa with immune checkpoint blockade in SCLC. While the SCLC models were refractory to anti-PD-1 or anti-CTLA4 monotherapy, anti-PD-1 and anti-CTLA4 combination immunotherapy (ITc) induced a significant antitumor response. Further, the Dasa+ITc combination was superior to ITc or Dasa alone. Dasa+ITc activity was mediated by CD4+ T cells, MHC-II+ antigen presenting cells (APCs), and natural killer (NK) cells, as depletion of these populations impeded the combination treatment antitumor efficacy. Increased tumor infiltration of CD4+ and CD8+ T cells, NK cells, M1-like macrophages, and CD11c+ APCs and a reduction of regulatory T cells (Tregs) and M2-like macrophages were found in Dasa+ITc-treated mice. Dasa increased CCL5 in NK cells and reduced Treg cell conversion from CD4+ lymphocytes. Dasa+ITc therapy elicited robust antitumor efficacy in 3D co-cultures of immune and SCLC cells. In vivo experiments showed that CCL5 was necessary for the Dasa+ITc response. In SCLC immunotherapy-treated patients, a gene signature including CD4, CIITA, and tumor mutational burden predicted good prognosis. On-treatment CCL5 plasma levels were increased only in patients with long progression-free survival, and pre-treatment secretomics identified cytokines related to myeloid cells significantly associated with poor prognosis. In summary, combining Dasa with immunotherapy represents a strategy to treat SCLC, with CCL5 as a cytokine that could serve to monitor response.

Supplementary Figure 4 from PTEN loss confers resistance to anti-PD-1 therapy in non-small cell lung cancer by increasing tumor infiltration of regulatory T cells