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.

Early alterations in cancer include the deregulation of epigenetic events such as changes in DNA methylation and abnormal levels of non-coding (nc)RNAs. Although these changes can be identified in tumors, alternative sources of samples may offer advantages over tissue biopsies. Because tumors shed DNA, RNA, and proteins, biological fluids containing these molecules can accurately reflect alterations found in cancer cells, not only coming from the primary tumor, but also from metastasis and from the tumor microenvironment (TME). Depending on the type of cancer, biological fluids encompass blood, urine, cerebrospinal fluid, and saliva, among others. Such samples are named with the general term “liquid biopsy” (LB). With the advent of ultrasensitive technologies during the last decade, the identification of actionable genetic alterations (i.e., mutations) in LB is a common practice to decide whether or not targeted therapy should be applied. Likewise, the analysis of global or specific epigenetic alterations may also be important as biomarkers for diagnosis, prognosis, and even for cancer drug response. Several commercial kits that assess the DNA promoter methylation of single genes or gene sets are available, with some of them being tested as biomarkers for diagnosis in clinical trials. From the tumors with highest incidence, we can stress the relevance of DNA methylation changes in the following genes found in LB: SHOX2 (for lung cancer); RASSF1A, RARB2, and GSTP1 (for lung, breast, genitourinary and colon cancers); and SEPT9 (for colon cancer). Moreover, multi-cancer high-throughput methylation-based tests are now commercially available. Increased levels of the microRNA miR21 and several miRNA- and long ncRNA-signatures can also be indicative biomarkers in LB. Therefore, epigenetic biomarkers are attractive and may have a clinical value in cancer. Nonetheless, validation, standardization, and demonstration of an added value over the common clinical practice are issues needed to be addressed in the transfer of this knowledge from “bench to bedside”.

YES1 is a nonreceptor tyrosine kinase that belongs to the SRC family of kinases (SFK) and controls multiple cancer signaling pathways. YES1 is amplified and overexpressed in many tumor types, where it promotes cell proliferation, survival, and invasiveness. Therefore, YES1 has been proposed as an emerging target in solid tumors. In addition, studies have shown that YES1 is a prognostic biomarker and a predictor of dasatinib activity. Several SFKs-targeting drugs have been developed, and some of them have reached clinical trials. However, these drugs have encountered challenges to their utilization in the clinical practice in unselected patients due to toxicity and lack of efficacy. In the case of YES1, novel specific inhibitors have been developed and tested in preclinical models, with impressive antitumor effects. In this review, we summarize the structure and activation of YES1 and describe its role in cancer as a target and prognostic and companion biomarker. We also address the efficacy of SFKs inhibitors that are currently in clinical trials, highlighting the main hindrances for their clinical use. Current available information strongly suggests that inhibiting YES1 in tumors with high expression of this protein is a promising strategy against cancer.

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.

Toll-like receptors (TLRs) are natural initial triggers of innate and adaptive immune responses. With the advent of cancer immunotherapy, nucleic acids engineered as ligands of endosomal TLRs have been investigated for the treatment of solid tumors. Despite promising results, their systemic administration, similarly to other immunotherapies, raises safety issues. To overcome these problems, recent studies have applied the direct injection of endosomal TLR agonists in the tumor and/or draining lymph nodes, achieving high local drug exposure and strong antitumor response. Importantly, intratumoral delivery of TLR agonists showed powerful effects not only against the injected tumors but also often against uninjected lesions (abscopal effects), resulting in some cases in cure and antitumoral immunological memory. Herein, we describe the structure and function of TLRs and their role in the tumor microenvironment. Then, we provide our vision on the potential of intratumor versus systemic delivery or vaccination approaches using TLR agonists, also considering the use of nanoparticles to improve their targeting properties. Finally, we collect the preclinical and clinical studies applying intratumoral injection of TLR agonists as monotherapies or in combination with: (a) other TLR or STING agonists; (b) other immunotherapies; (c) radiotherapy or chemotherapy; (d) targeted therapies.