Loss of Lkb1 and Pten leads to lung squamous cell carcinoma with elevated PD-L1 expression

The Tumor Suppressor PTEN as Molecular Switch Node Regulating Cell Metabolism and Autophagy: Implications in Immune System and Tumor Microenvironment

Recent studies conducted over the past 10 years evidence the intriguing role of the tumor suppressor gene Phosphatase and Tensin Homolog deleted on Chromosome 10 PTEN in the regulation of cellular energy expenditure, together with its capability to modulate proliferation and survival, thus expanding our knowledge of its physiological functions. Transgenic PTEN mice models are resistant to oncogenic transformation, present decreased adiposity and reduced cellular glucose and glutamine uptake, together with increased mitochondrial oxidative phosphorylation. These acquisitions led to a novel understanding regarding the role of PTEN to counteract cancer cell metabolic reprogramming. Particularly, PTEN drives an “anti-Warburg state” in which less glucose is taken up, but it is more efficiently directed to the mitochondrial Krebs cycle. The maintenance of cellular homeostasis together with reduction of metabolic stress are controlled by specific pathways among which autophagy, a catabolic process strictly governed by mTOR and PTEN. Besides, a role of PTEN in metabolic reprogramming and tumor/stroma interactions in cancer models, has recently been established. The genetic inactivation of PTEN in stromal fibroblasts of mouse mammary glands, accelerates breast cancer initiation and progression. This review will discuss our novel understanding in the molecular connection between cell metabolism and autophagy by PTEN, highlighting novel implications regarding tumor/stroma/immune system interplay. The newly discovered action of PTEN opens innovative avenues for investigations relevant to counteract cancer development and progression.

Combining protein arginine methyltransferase inhibitor and anti-programmed death-ligand-1 inhibits pancreatic cancer progression

BACKGROUND

Immunotherapy targeting programmed death-1 (PD-1) or programmed death-ligand-1 (PD-L1) has been shown to be effective in a variety of malignancies but has poor efficacy in pancreatic ductal adenocarcinoma (PDAC). Studies have shown that PD-L1 expression in tumors is an important indicator of the efficacy of immunotherapy. Tumor cells usually evade chemotherapy and host immune surveillance by epigenetic changes. Protein arginine methylation is a common posttranslational modification. Protein arginine methyltransferase (PRMT) 1 is deregulated in a wide variety of cancer types, whose biological role in tumor immunity is undefined.

AIM

To investigate the combined effects and underlying mechanisms of anti-PD-L1 and type I PRMT inhibitor in pancreatic cancer in vivo.

METHODS

PT1001B is a novel type I PRMT inhibitor with strong activity and good selectivity. A mouse model of subcutaneous Panc02-derived tumors was used to evaluate drug efficacy, toxic and side effects, and tumor growth in vivo. By flow cytometry, we determined the expression of key immune checkpoint proteins, detected the apoptosis in tumor tissues, and analyzed the immune cells. Immunohistochemistry staining for cellular proliferation-associated nuclear protein Ki67, TUNEL assay, and PRMT1/PD-L1 immunofluorescence were used to elucidate the underlying molecular mechanism of the antitumor effect.

RESULTS

Cultured Panc02 cells did not express PD-L1 in vitro, but tumor cells derived from Panc02 transplanted tumors expressed PD-L1. The therapeutic efficacy of anti-PD-L1 mAb was significantly enhanced by the addition of PT1001B as measured by tumor volume (1054.00 ± 61.37 mm³vs 555.80 ± 74.42 mm³, P < 0.01) and tumor weight (0.83 ± 0.06 g vs 0.38 ± 0.02 g, P < 0.05). PT1001B improved antitumor immunity by inhibiting PD-L1 expression on tumor cells (32.74% ± 5.89% vs 17.95% ± 1.92%, P < 0.05). The combination therapy upregulated tumor-infiltrating CD8+ T lymphocytes (23.75% ± 3.20% vs 73.34% ± 4.35%, P < 0.01) and decreased PD-1+ leukocytes (35.77% ± 3.30% vs 6.48% ± 1.08%, P < 0.001) in tumor tissue compared to the control. In addition, PT1001B amplified the inhibitory effect of anti-PD-L1 on tumor cell proliferation and enhanced the induction of tumor cell apoptosis. PRMT1 downregulation was correlated with PD-L1 downregulation.

CONCLUSION

PT1001B enhances antitumor immunity and combining it with anti-PD-L1 checkpoint inhibitors provides a potential strategy to overcome anti-PD-L1 resistance in PDAC.

LKB1 inhibits intrahepatic cholangiocarcinoma by repressing the transcriptional activity of the immune checkpoint PD-L1

AIMS

Intrahepatic cholangiocarcinoma (ICC) is a highly malignant tumour with increasing incidence and high mortality. Liver kinase B1 (LKB1) regulates cellular energy metabolism and cell division and affects immune microenvironment. This study aimed to uncover the underlying function and mechanism of LKB1 in ICC.

MAIN METHODS

To determine the correlation between LKB1 levels and clinicopathological features, the expression profile of LKB1 in ICC tissue specimens was examined by qRT-PCR and western blotting. In vitro experiments were conducted to examine the anticancer effect of LKB1 in ICC. Changes in the expression of epithelial-mesenchymal transition (EMT)-associated markers and immune checkpoints were analysed by qRT-PCR, western blotting, immunofluorescence and flow cytometry. The influence of LKB1 on the transcriptional activity of PD-L1 was determined by dual-luciferase reporter assays and IFNγ induction.

KEY FINDINGS

LKB1 was expressed at low levels in ICC and tightly associated with poor prognosis. LKB1 knockdown promoted the proliferation, migration, matrix adhesion and EMT of ICC cells. Notably, LKB1 silencing upregulated the surface expression of PD-L1 in ICC cells. Suppressed and mutated LKB1 enhanced the transcriptional activity of PD-L1 in ICC cells, leading to high expression of the immune checkpoint PD-L1. Furthermore, inhibiting LKB1 suppressed ICC cell apoptosis induced by IFNγ.

SIGNIFICANCE

By suppressing malignant transformation and the immune checkpoint PD-L1 of cancer cells, LKB1 plays an important role in inhibiting ICC and is a potential target for clinical diagnosis and treatment. This study may provide new strategies for improving the efficiency of cancer immunotherapy.

Tumor Cell-Intrinsic Immunometabolism and Precision Nutrition in Cancer Immunotherapy

One of the greatest challenges in the cancer immunotherapy field is the need to biologically rationalize and broaden the clinical utility of immune checkpoint inhibitors (ICIs). The balance between metabolism and immune response has critical implications for overcoming the major weaknesses of ICIs, including their lack of universality and durability. The last decade has seen tremendous advances in understanding how the immune system's ability to kill tumor cells requires the conspicuous metabolic specialization of T-cells. We have learned that cancer cell-associated metabolic activities trigger shifts in the abundance of some metabolites with immunosuppressory roles in the tumor microenvironment. Yet very little is known about the tumor cell-intrinsic metabolic traits that control the immune checkpoint contexture in cancer cells. Likewise, we lack a comprehensive understanding of how systemic metabolic perturbations in response to dietary interventions can reprogram the immune checkpoint landscape of tumor cells. We here review state-of-the-art molecular- and functional-level interrogation approaches to uncover how cell-autonomous metabolic traits and diet-mediated changes in nutrient availability and utilization might delineate new cancer cell-intrinsic metabolic dependencies of tumor immunogenicity. We propose that clinical monitoring and in-depth molecular evaluation of the cancer cell-intrinsic metabolic traits involved in primary, adaptive, and acquired resistance to cancer immunotherapy can provide the basis for improvements in therapeutic responses to ICIs. Overall, these approaches might guide the use of metabolic therapeutics and dietary approaches as novel strategies to broaden the spectrum of cancer patients and indications that can be effectively treated with ICI-based cancer immunotherapy.

Generation of Genetically Engineered Mouse Lung Organoid Models for Squamous Cell Lung Cancers Allows for the Study of Combinatorial Immunotherapy

PURPOSE

Lung squamous cell carcinoma (LSCC) is a deadly disease for which only a subset of patients responds to immune checkpoint blockade (ICB) therapy. Therefore, preclinical mouse models that recapitulate the complex genetic profile found in patients are urgently needed.

EXPERIMENTAL DESIGN

We used CRISPR genome editing to delete multiple tumor suppressors in lung organoids derived from Cre-dependent SOX2 knock-in mice. We investigated both the therapeutic efficacy and immunologic effects accompanying combination PD-1 blockade and WEE1 inhibition in both mouse models and LSCC patient-derived cell lines.

RESULTS

We show that multiplex gene editing of mouse lung organoids using the CRISPR-Cas9 system allows for efficient and rapid means to generate LSCCs that closely mimic the human disease at the genomic and phenotypic level. Using this genetically defined mouse model and three-dimensional tumoroid culture system, we show that WEE1 inhibition induces DNA damage that primes the endogenous type I IFN and antigen presentation system in primary LSCC tumor cells. These events promote cytotoxic T-cell-mediated clearance of tumor cells and reduce the accumulation of tumor-infiltrating neutrophils. Beneficial immunologic features of WEE1 inhibition are further enhanced by the addition of anti-PD-1 therapy.

CONCLUSIONS

We developed a mouse model system to investigate a novel combinatory approach that illuminates a clinical path hypothesis for combining ICB with DNA damage-inducing therapies in the treatment of LSCC.

Regulating tumor suppressor genes: post-translational modifications

Tumor suppressor genes cooperate with each other in tumors. Three important tumor suppressor proteins, retinoblastoma (Rb), p53, phosphatase, and tensin homolog deleted on chromosome ten (PTEN) are functionally associated and they regulated by post-translational modification (PTMs) as well. PTMs include phosphorylation, SUMOylation, acetylation, and other novel modifications becoming growing appreciated. Because most of PTMs are reversible, normal cells use them as a switch to control the state of cells being the resting or proliferating, and PTMs also involve in cell survival and cell cycle, which may lead to abnormal proliferation and tumorigenesis. Although a lot of studies focus on the importance of each kind of PTM, further discoveries shows that tumor suppressor genes (TSGs) form a complex "network" by the interaction of modification. Recently, there are several promising strategies for TSGs for they change more frequently than carcinogenic genes in cancers. We here review the necessity, characteristics, and mechanisms of each kind of post-translational modification on Rb, p53, PTEN, and its influence on the precise and selective function. We also discuss the current antitumoral therapies of Rb, p53 and PTEN as predictive, prognostic, and therapeutic target in cancer.

Emerging role of PTEN loss in evasion of the immune response to tumours

Mutations in PTEN activate the phosphoinositide 3-kinase (PI3K) signalling network, leading to many of the characteristic phenotypic changes of cancer. However, the primary effects of this gene on oncogenesis through control of the PI3K-AKT-mammalian target of rapamycin (mTOR) pathway might not be the only avenue by which PTEN affects tumour progression. PTEN has been shown to regulate the antiviral interferon network and thus alter how cancer cells communicate with and are targeted by immune cells. An active, T cell-infiltrated microenvironment is critical for immunotherapy success, which is also influenced by mutations in DNA damage repair pathways and the overall mutational burden of the tumour. As PTEN has a role in the maintenance of genomic integrity, it is likely that a loss of PTEN affects the immune response at two different levels and might therefore be instrumental in mediating failed responses to immunotherapy. In this review, we summarise findings that demonstrate how the loss of PTEN function elicits specific changes in the immune response in several types of cancer. We also discuss ongoing clinical trials that illustrate the potential utility of PTEN as a predictive biomarker for immune checkpoint blockade therapies.

PPARG Could Work as a Valid Therapeutic Strategy for the Treatment of Lung Squamous Cell Carcinoma

Previous studies showed that PPAR-gamma (PPARG) ligands might serve as potential therapeutic agents for nonsmall cell lung cancer (NSCLC). However, a few studies reported the specific relationship between PPARG and lung squamous cell carcinoma (LSCC). Here, we made an effort to explore the relationship between PPARG and LSCC. First, we used mega-analysis and partial mega-analysis to analyze the effects of PPARG on LSCC by using 12 independent LSCC expression datasets (285 healthy controls and 375 LSCC cases). Then, literature-based molecular pathways between PPARG and LSCC were established. After that, a gene set enrichment analysis (GSEA) was conducted to study the functionalities of PPARG and PPARG-driven triggers within the molecular pathways. Finally, another mega-analysis was constructed to test the expression changes of PPARG and its driven targets. The partial mega-analysis showed a significant downregulated expression of PPARG in LSCC (LFC = -1.08, p value = 0.00073). Twelve diagnostic markers and four prognostic markers were identified within multiple PPARG-LSCC regulatory pathways. Our results suggested that the activation of PPARG expression may inhibit the development and progression of LSCC through the regulation of LSCC upstream regulators and downstream marker genes, which were involved in tumor cell proliferation and protein polyubiquitination/ubiquitination.

Association of Programmed Death-Ligand 1 Expression with Fusion Variants and Clinical Outcomes in Patients with Anaplastic Lymphoma Kinase-Positive Lung Adenocarcinoma Receiving Crizotinib

BACKGROUND

Programmed death-ligand 1 (PD-L1) expression is associated with clinical outcomes of epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma (ADC) treated with tyrosine kinase inhibitors (TKIs). However, whether PD-L1 expression plays a role in anaplastic lymphoma kinase (ALK)-positive lung ADC is unknown. We aimed to evaluate the impact of PD-L1 in patients with ALK-positive lung ADC receiving crizotinib.

MATERIALS AND METHODS

PD-L1 expression was identified by immunohistochemistry (IHC). Reverse transcriptase-polymerase chain reaction was used for ALK variant detection, and immunofluorescence-based multiplex staining was applied for exploring immune cells in tumor microenvironments.

RESULTS

A total of 78 patients with ALK-positive advanced ADC were enrolled in our study, of whom 52 received crizotinib. Compared with EGFR/ALK wild-type tumors, PD-L1 expression was lower in ALK-positive ADC. ALK fusion variants were identified in 32 patients, and those with variant 3 and 5 (short variants) had higher PD-L1 expression than those with other variants. The crizotinib objective response rate (ORR) and progression-free survival (PFS) was better in tumors with negative PD-L1 expression (ORR/PFS in PD-L1 0% vs. 1%-49% vs. 50%-100%: 60.7%/11.8 months vs. 38.5%/6.5 months vs. 36.4%/4.0 months, p = .007/.022). The multivariate Cox proportional hazards model revealed that PD-L1 0% (vs. ≥1%) was an independent factor for longer PFS (adjusted hazard ratio 0.322, 95% confidence interval 0.160-0.650, p = .002). Multiplex IHC in three cases showed a varied extent of immune cell infiltrations in tumors with different PD-L1 expression.

CONCLUSION

Positive PD-L1 expression was associated with unfavorable clinical outcomes in patients with ALK-positive lung ADC receiving crizotinib.

IMPLICATIONS FOR PRACTICE

Not all lung adenocarcinoma with sensitizing driver mutations experienced durable responses to small-molecule tyrosine kinase inhibitors (TKIs). Similar to the negative impact of programmed death-ligand 1 (PD-L1) in epidermal growth factor receptor mutant tumors treated with TKIs, this study demonstrated that positive PD-L1 expression was also associated with worse response rate and shorter progression-free survival of anaplastic lymphoma kinase (ALK)-positive adenocarcinoma treated with crizotinib. Among different ALK fusion partners, tumors with short variants (V3 and V5) had higher PD-L1 compared with long variants (V1, V2, and V6). Testing PD-L1 before initiating crizotinib for ALK-positive lung cancer could be a simple method to provide important prognostic information.

Clinicopathological and genomic correlates of programmed cell death ligand 1 (PD-L1) expression in nonsquamous non-small-cell lung cancer

BACKGROUND

Programmed cell death ligand 1 (PD-L1) tumor proportion score (TPS) is the primary clinically-available biomarker of response to immunotherapy in non-small-cell lung cancer (NSCLC), but factors associated with PD-L1 expression are not well understood.

MATERIALS AND METHODS

Consecutive nonsquamous NSCLCs with successful PD-L1 assessment and targeted next-generation sequencing were included in this retrospective study. Clinicopathological characteristics, gene mutations, and copy number changes in gene and chromosomal arms were compared among three PD-L1 expression groups: negative (TPS < 1%), low (TPS 1%-49%), and high (TPS ≥ 50%). A Q-value <0.25 was considered significant after multiple comparisons correction.

RESULTS

A total of 909 nonsquamous NSCLCs were included. High PD-L1 expression compared with low and negative PD-L1 expression was associated with increased tobacco exposure (median pack-years: 25 versus 20 versus 20, respectively; P = 0.01), advanced stage at diagnosis (76% versus 67% versus 61% with advanced stage of disease, respectively; P < 0.001), and higher tumor mutational burden (TMB) (median 12.2 versus 10.6 versus 10.6 mutations/megabase, respectively; P < 0.001). Negative PD-L1 expression when compared with high PD-L1 expression was associated with: mutations in STK11 (19% versus 5%; Q < 0.001), EGFR (22% versus 11%; Q < 0.001), CTNNB1 (4.3% versus 0.4%; Q = 0.04), APC (5% versus 1%; Q = 0.17), and SMARCA4 (9% versus 4%; Q = 0.20); copy number loss of CD274 (PD-L1, 28% versus 6%; Q < 0.001), PDCD1LG2 (PD-L2, 28% versus 6%; Q < 0.001), and JAK2 genes (27% versus 7%; Q < 0.001), loss of chromosomal arm 9p (23% versus 10%; Q = 0.04), and gain of 1q (46% versus 21%; Q < 0.001). High PD-L1 expression compared with negative PD-L1 expression was associated with copy number gain of CD274 (11% versus 3%; Q = 0.01) and PDCD1LG2 (11% versus 3%; Q = 0.01). NSCLCs with CD274 loss, compared with those without loss, had a lower response rate (23% versus 9%; P = 0.006) and shorter progression-free survival (3.3 versus 2.0 months; P = 0.002) on immunotherapy.

CONCLUSIONS

PD-L1 expression is associated with specific genomic alterations and clinicopathologic characteristics in nonsquamous NSCLC.

Squamous trans-differentiation of pancreatic cancer cells promotes stromal inflammation

A highly aggressive subset of pancreatic ductal adenocarcinomas undergo trans-differentiation into the squamous lineage during disease progression. Here, we investigated whether squamous trans-differentiation of human and mouse pancreatic cancer cells can influence the phenotype of non-neoplastic cells in the tumor microenvironment. Conditioned media experiments revealed that squamous pancreatic cancer cells secrete factors that recruit neutrophils and convert pancreatic stellate cells into cancer-associated fibroblasts (CAFs) that express inflammatory cytokines at high levels. We use gain- and loss-of-function approaches to show that squamous-subtype pancreatic tumor models become enriched with neutrophils and inflammatory CAFs in a p63-dependent manner. These effects occur, at least in part, through p63-mediated activation of enhancers at pro-inflammatory cytokine loci, which includes IL1A and CXCL1 as key targets. Taken together, our findings reveal enhanced tissue inflammation as a consequence of squamous trans-differentiation in pancreatic cancer, thus highlighting an instructive role of tumor cell lineage in reprogramming the stromal microenvironment.

Maintaining protein stability of ∆Np63 via USP28 is required by squamous cancer cells

The transcription factor ∆Np63 is a master regulator of epithelial cell identity and essential for the survival of squamous cell carcinoma (SCC) of lung, head and neck, oesophagus, cervix and skin. Here, we report that the deubiquitylase USP28 stabilizes ∆Np63 and maintains elevated ∆NP63 levels in SCC by counteracting its proteasome-mediated degradation. Impaired USP28 activity, either genetically or pharmacologically, abrogates the transcriptional identity and suppresses growth and survival of human SCC cells. CRISPR/Cas9-engineered in vivo mouse models establish that endogenous USP28 is strictly required for both induction and maintenance of lung SCC. Our data strongly suggest that targeting ∆Np63 abundance via inhibition of USP28 is a promising strategy for the treatment of SCC tumours.

The Inhibitory Mechanisms of Tumor PD-L1 Expression by Natural Bioactive Gallic Acid in Non-Small-Cell Lung Cancer (NSCLC) Cells

Non-small-cell lung cancer (NSCLC) is the most common lung cancer subtype and accounts for more than 80% of all lung cancer cases. Epidermal growth factor receptor (EGFR) phosphorylation by binding growth factors such as EGF activates downstream prooncogenic signaling pathways including KRAS-ERK, JAK-STAT, and PI3K-AKT. These pathways promote the tumor progression of NSCLC by inducing uncontrolled cell cycle, proliferation, migration, and programmed death-ligand 1 (PD-L1) expression. New cytotoxic drugs have facilitated considerable progress in NSCLC treatment, but side effects are still a significant cause of mortality. Gallic acid (3,4,5-trihydroxybenzoic acid; GA) is a phenolic natural compound, isolated from plant derivatives, that has been reported to show anticancer effects. We demonstrated the tumor-suppressive effect of GA, which induced the decrease of PD-L1 expression through binding to EGFR in NSCLC. This binding inhibited the phosphorylation of EGFR, subsequently inducing the inhibition of PI3K and AKT phosphorylation, which triggered the activation of p53. The p53-dependent upregulation of miR-34a induced PD-L1 downregulation. Further, we revealed the combination effect of GA and anti-PD-1 monoclonal antibody in an NSCLC-cell and peripheral blood mononuclear-cell coculture system. We propose a novel therapeutic application of GA for immunotherapy and chemotherapy in NSCLC.

Integrative Analysis of Methylation and Gene Expression in Lung Adenocarcinoma and Squamous Cell Lung Carcinoma

Lung cancer is a highly prevalent type of cancer with a poor 5-year survival rate of about 4-17%. Eighty percent lung cancer belongs to non-small-cell lung cancer (NSCLC). For a long time, the treatment of NSCLC has been mostly guided by tumor stage, and there has been no significant difference between the therapy strategy of lung adenocarcinoma (LUAD) and squamous cell lung carcinoma (SCLC), the two major subtypes of NSCLC. In recent years, important molecular differences between LUAD and SCLC are increasingly identified, indicating that targeted therapy will be more and more histologically specific in the future. To investigate the LUAD and SCLC difference on multi-omics scale, we analyzed the methylation and gene expression data together. With the Boruta method to remove irrelevant features and the MCFS (Monte Carlo Feature Selection) method to identify the significantly important features, we identified 113 key methylation features and 23 key gene expression features. HNF1B and TP63 were found to be dysfunctional on both methylation and gene expression levels. The experimentally determined interaction network suggested that TP63 may play an important role in connecting methylation genes and expression genes. Many of the discovered signature genes have been supported by literature. Our results may provide directions of precision diagnosis and therapy of LUAD and SCLC.

FGD1 promotes tumor progression and regulates tumor immune response in osteosarcoma via inhibiting PTEN activity

Rationale: Mesenchymal cell-derived osteosarcoma is a rare malignant bone tumor affecting children and adolescents. PTEN down-regulation or function-loss mutation is associated with the aggressive of osteosarcoma. Explicating the regulatory mechanism of PTEN might highlight new targets for improving the survival rate of osteosarcoma patients.

Methods: The clinical relevance of FGD1 was examined by the TCGA data set, Western blotting and immunohistochemistry of osteosarcoma microarray slides. Functional assays, such as the MTS assay, colony formation assay and xenografts, were used to determine the biological role of FGD1 in osteosarcoma. The protein-protein interaction between FGD1 and PTEN was detected via co-immunoprecipitation. The relationship between FGD1 and PD-L1 was examined by Western blot analysis, RT-qPCR and immunohistochemistry.

Results: In this study, analysis of the TCGA data set of sarcomas revealed that FGD1 was over-expressed with the highest P values. Then, we demonstrated that FGD1 was also abnormally up-regulated in osteosarcoma with unfavorable prognosis. Aberrant expressed FGD1 promoted the osteosarcoma tumor cell proliferation and invasion. Moreover, we found that FGD1 was participated in activating PI3K/AKT signaling pathway by interacting with PTEN. Finally, we showed that FGD1 was capable of regulating the tumor immune response via the PTEN/PD-L1 axis in osteosarcoma.

Conclusions: Our data suggested that abnormally over-expressed FGD1 functions as an oncogenic protein to promote osteosarcoma progression through inhibiting PTEN activity and activating PI3K/AKT signaling. Notably, FGD1 increased PD-L1 expression in a PTEN dependent manner and modulated the sensitivity of immune checkpoint-based immunotherapy in osteosarcoma. Thus, FGD1 might be a potential target for improving the survival rate of osteosarcomas.

Is there a causal link between PTEN deficient tumors and immunosuppressive tumor microenvironment?

The PTEN tumor suppressor is the second most commonly inactivated gene across cancer types. While it's role in PI3K/AKT and DNA damage pathways are clear, increasing evidences suggest that PTEN may also promote anti-tumor immunity. PTEN-deficient tumors are characterized by (i) reduced levels of cytotoxic T cells, helper T cells and NK cells, (ii) elevated pro-oncogenic inflammatory cytokines like CCL2 and (iii) increased levels of immunosuppressive cells such as MDSCs and Tregs. An intriguing possibility is that link between PTEN and anti-tumor immunity is mediated by the interferon signaling pathway. In this review, we summarize the evidences for the mechanistic link between PTEN deficiency and immunosuppressive tumor microenvironment and the interferon signaling pathway. We further discuss how the link between these pathways can be exploited for development of personalized immunotherapy for patients with PTEN deficient tumors.

MicroRNA-200a induces immunosuppression by promoting PTEN-mediated PD-L1 upregulation in osteosarcoma

In this study, we identified microRNAs that regulate the expression of programmed death-ligand 1(PD-L1) in osteosarcoma and investigated their role in PD-L1-targeted immunotherapy. MicroRNA sequencing analysis showed that the expression of PD-L1 is regulated by microRNA-200a in U2OS, 143B, and K7 osteosarcoma cells. MicroRNA-200a overexpression induced the upregulation of PD-L1 in the osteosarcoma cells. CD8⁺ T cells co-cultured with microRNA-200a-overexpressing osteosarcoma cells showed reduced survival, proliferation, and secretion of granzyme B and perforin. The same phenomenon was also observed in the K7-derived syngeneic mouse model, as microRNA-200a promoted tumor growth by increasing the percentage of Foxp3⁺ regulatory T lymphocytes while reducing the proportions of CD4⁺, CD8⁺, and IFN-γ⁺ cytotoxic T lymphocytes. But microRNA-200a overexpression group was also more responsive to PD-L1-targeted immunotherapy than the controls. In addition, the tumor tissues from 32 osteosarcoma patients showed that high expression of microRNA-200a and PD-L1 was associated with poor tumor necrosis rate after chemotherapy. Moreover, we confirmed that tensin homolog deleted on chromosome ten (PTEN) could act as the target gene for microRNA-200a during the upregulation of PD-L1. Thus, our findings provide important and novel insight into a regulatory axis involving microRNA-200a/PTEN/ PD-L1 axis, which determines osteosarcoma growth and the efficacy of PD-L1-targeted immunotherapy.

Roles of circRNAs in the tumour microenvironment

The tumour microenvironment (TME) constitutes the area surrounding the tumour during its development and has been demonstrated to play roles in cancer-related diseases through crosstalk with tumour cells. Circular RNAs (circRNAs) are a subpopulation of endogenous noncoding RNAs (ncRNAs) that are ubiquitously expressed in eukaryotes and have multiple biological functions in the regulation of cancer onset and progression. An increasing number of studies have shown that circRNAs participate in the multifaceted biological regulation of the TME. However, details on the mechanisms involved have remained elusive until now. In this review, we analyse the effects of circRNAs on the TME from various perspectives, including immune surveillance, angiogenesis, hypoxia, matrix remodelling, exo-circRNAs and chemoradiation resistance. Currently, the enormous potential for circRNA use in targeted therapy and as noninvasive biomarkers have drawn our attention. We emphasize the prospect of targeting circRNAs as an essential strategy to regulate TME, overcome cancer resistance and improve therapeutic outcomes.

Chromosome 3q26 Gain Is an Early Event Driving Coordinated Overexpression of the PRKCI, SOX2, and ECT2 Oncogenes in Lung Squamous Cell Carcinoma

Lung squamous cell carcinoma (LSCC) is a prevalent form of lung cancer exhibiting distinctive histological and genetic characteristics. Chromosome 3q26 copy number gain (CNG) is a genetic hallmark of LSCC present in >90% of tumors. We report that 3q26 CNGs occur early in LSCC tumorigenesis, persist during tumor progression, and drive coordinate overexpression of PRKCI, SOX2, and ECT2. Overexpression of PRKCI, SOX2, and ECT2 in the context of Trp53 loss is sufficient to transform mouse lung basal stem cells into tumors with histological and genomic features of LSCC. Functionally, PRKCI and SOX2 collaborate to activate an extensive transcriptional program that enforces a lineage-restricted LSCC phenotype, whereas PRKCI and ECT2 collaborate to promote oncogenic growth. Gene signatures indicative of PKCι-SOX2 and PKCι-ECT2 signaling activity are enriched in the classical subtype of human LSCC and predict distinct therapeutic vulnerabilities. Thus, the PRKCI, SOX2, and ECT2 oncogenes represent a multigenic driver of LSCC.

Roles of PD-1/PD-L1 Pathway: Signaling, Cancer, and Beyond

Immunotherapies that target PD-1/PD-L1 axis have shown unprecedented success in a wide variety of human cancers. PD-1 is one of the key coinhibitory receptors expressed on T cells upon T cell activation. After engagement with its ligands, mainly PD-L1, PD-1 is activated and recruits the phosphatase SHP-2 in proximity to T cell receptor (TCR) and CD28 signaling. This event results in dephosphorylation and attenuation of key molecules in TCR and CD28 pathway, leading to inhibition of T cell proliferation, activation, cytokine production, altered metabolism and cytotoxic T lymphocytes (CTLs) killer functions, and eventual death of activated T cells. Bodies evolve coinhibitory pathways controlling T cell response magnitude and duration to limit tissue damage and maintain self-tolerance. However, tumor cells hijack these inhibitory pathways to escape host immune surveillance by overexpression of PD-L1. This provides the scientific rationale for clinical application of immune checkpoint inhibitors in oncology. The aberrantly high expression of PD-L1 in tumor microenvironment (TME) can be attributable to the "primary" activation of multiple oncogenic signaling and the "secondary" induction by inflammatory factors such as IFN-γ. Clinically, antibodies targeting PD-1/PD-L1 reinvigorate the "exhausted" T cells in TME and show remarkable objective response and durable remission with acceptable toxicity profile in large numbers of tumors such as melanoma, lymphoma, and mismatch-repair deficient tumors. Nevertheless, most patients are still refractory to anti-PD-1/PD-L1 therapy. Identifying the predictive biomarkers and design rational PD-1-based combination therapy become the priorities in cancer immunotherapy. PD-L1 expression, cytotoxic T lymphocytes infiltration, and tumor mutation burden (TMB) are generally considered as the most important factors affecting the effectiveness of PD-1/PD-L1 blockade. The revolution in cancer immunotherapy achieved by PD-1/PD-L1 blockade offers the paradigm for scientific translation from bench to bedside. The next decades will without doubt witness the renaissance of immunotherapy.

Hepatitis B virus-triggered PTEN/β-catenin/c-Myc signaling enhances PD-L1 expression to promote immune evasion

Hepatitis B virus (HBV) exploits multiple strategies to evade host immune surveillance. Programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) signaling plays a critical role in regulating T cell homeostasis. However, it remains largely unknown as to how HBV infection elevates PD-L1 expression in hepatocytes. A mouse model of HBV infection was established by hydrodynamic injection with a vector containing 1.3-fold overlength HBV genome (pHBV1.3) via the tail vein. Coculture experiments with HBV-expressing hepatoma cells and Jurkat T cells were established in vitro. We observed significant decrease in the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and increase in β-catenin/PD-L1 expression in liver tissues from patients with chronic hepatitis B and mice subjected to pHBV1.3 hydrodynamic injection. Mechanistically, decrease in PTEN enhanced β-catenin/c-Myc signaling and PD-L1 expression in HBV-expressing hepatoma cells, which in turn augmented PD-1 expression, lowered IL-2 secretion, and induced T cell apoptosis. However, β-catenin disruption inhibited PTEN-mediated PD-L1 expression, which was accompanied by decreased PD-1 expression, and increased IL-2 production in T cells. Luciferase reporter assays revealed that c-Myc stimulated transcriptional activity of PD-L1. In addition, HBV X protein (HBx) and HBV polymerase (HBp) contributed to PTEN downregulation and β-catenin/PD-L1 upregulation. Strikingly, PTEN overexpression in hepatocytes inhibited β-catenin/PD-L1 signaling and promoted HBV clearance in vivo. Our findings suggest that HBV-triggered PTEN/β-catenin/c-Myc signaling via HBx and HBp enhances PD-L1 expression, leading to inhibition of T cell response, and promotes HBV immune evasion.NEW & NOTEWORTHY This study demonstrates that during HBV infection, HBV can increase PD-L1 expression via PTEN/β-catenin/c-Myc signaling pathway, which in turn inhibits T cell response and ultimately promotes HBV immune evasion. Targeting this signaling pathway is a potential strategy for immunotherapy of chronic hepatitis B.

Functions of Immune Checkpoint Molecules Beyond Immune Evasion

Immune checkpoint molecules, including inhibitory and stimulatory immune checkpoint molecules, are defined as ligand-receptor pairs that exert inhibitory or stimulatory effects on immune responses. Most of the immune checkpoint molecules that have been described so far are expressed on cells of the adaptive immune system, particularly on T cells, and of the innate immune system. They are crucial for maintaining the self-tolerance and modulating the length and magnitude of immune responses of effectors in different tissues to minimize the tissue damage. More and more evidences have shown that inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor types. Although the main function of tumor cell-associated immune checkpoint molecules is considered to mediate the immune evasion, it has been reported that the immune checkpoint molecules expressed on tumor cells also play important roles in the maintenance of many malignant behaviors, including self-renewal, epithelial-mesenchymal transition, metastasis, drug resistance, anti-apoptosis, angiogenesis, or enhanced energy metabolisms. In this section, we mainly focus on delineating the roles of the tumor cell-associated immune checkpoint molecules beyond immune evasion, such as PD-L1, PD-1, B7-H3, B7-H4, LILRB1, LILRB2, TIM3, CD47, CD137, and CD70.

[Advances in the Influence of EGFR Mutation on the PD-L1 Expression in Non-small Cell Lung Cancer]

近年来，有关程序性死亡受体1（programmed death-1, PD-1）及其配体（programmed death-1 ligand, PD-L1）抑制剂的研究取得突破性进展，迅速改变着非小细胞肺癌（non-small cell lung cancer, NSCLC）的治疗模式。但表皮生长因子受体（epidermal growth factor receptor, EGFR）突变患者应用PD-1/PD-L1抑制剂的治疗效果并不理想。既往研究显示，肿瘤细胞PD-L1表达率与免疫抑制剂治疗效果存在相关性。但目前EGFR突变对PD-L1表达的影响并不能达成一致。我们将对相关研究进行总结，以期对基础研究或临床治疗有所帮助。

Neutrophil content predicts lymphocyte depletion and anti-PD1 treatment failure in NSCLC

Immune checkpoint inhibitor (ICI) treatment has recently become a first-line therapy for many non-small cell lung cancer (NSCLC) patients. Unfortunately, most NSCLC patients are refractory to ICI monotherapy, and initial attempts to address this issue with secondary therapeutics have proven unsuccessful. To identify entities precluding CD8+ T cell accumulation in this process, we performed unbiased analyses on flow cytometry, gene expression, and multiplexed immunohistochemical data from a NSCLC patient cohort. The results revealed the presence of a myeloid-rich subgroup, which was devoid of CD4+ and CD8+ T cells. Of all myeloid cell types assessed, neutrophils were the most highly associated with the myeloid phenotype. Additionally, the ratio of CD8+ T cells to neutrophils (CD8/PMN) within the tumor mass optimally distinguished between active and myeloid cases. This ratio was also capable of showing the separation of patients responsive to ICI therapy from those with stable or progressive disease in 2 independent cohorts. Tumor-bearing mice treated with a combination of anti-PD1 and SX-682 (CXCR1/2 inhibitor) displayed relocation of lymphocytes from the tumor periphery into a malignant tumor, which was associated with induction of IFN-γ-responsive genes. These results suggest that neutrophil antagonism may represent a viable secondary therapeutic strategy to enhance ICI treatment outcomes.

TBKBP1 and TBK1 form a growth factor signalling axis mediating immunosuppression and tumourigenesis

The kinase TBK1 responds to microbial stimuli and mediates type I interferon (IFN-I) induction. We show that TBK1 is also a central mediator of growth factor signaling; this function relies on a specific adaptor, TBK-binding protein 1 (TBKBP1). TBKBP1 recruits TBK1 to PKCθ via a scaffold protein, Card10, which allows PKCθ to phosphorylate TBK1 at serine-716, a crucial step for TBK1 activation by growth factors but not by innate immune stimuli. While the TBK1/TBKBP1 signaling axis is dispensable for IFN-I induction, it mediates mTORC1 activation and oncogenesis. Lung epithelial cell-conditional deletion of either TBK1 or TBKBP1 inhibits tumorigenesis in a mouse model of lung cancer. In addition to promoting tumor growth, the TBK1/TBKBP1 axis facilitates tumor-mediated immunosuppression by a mechanism involving induction of the checkpoint molecule PD-L1 and stimulation of glycolysis. These findings suggest a PKCθ-TBKBP1-TBK1 growth factor signaling axis mediating both tumor growth and immunosuppression.

Tumor-intrinsic signaling pathways: key roles in the regulation of the immunosuppressive tumor microenvironment

Immunotherapy is a currently popular treatment strategy for cancer patients. Although recent developments in cancer immunotherapy have had significant clinical impact, only a subset of patients exhibits clinical response. Therefore, understanding the molecular mechanisms of immunotherapy resistance is necessary. The mechanisms of immune escape appear to consist of two distinct tumor characteristics: a decrease in effective immunocyte infiltration and function and the accumulation of immunosuppressive cells in the tumor microenvironment. Several host-derived factors may also contribute to immune escape. Moreover, inter-patient heterogeneity predominantly results from differences in somatic mutations between cancers, which has led to the hypothesis that differential activation of specific tumor-intrinsic pathways may explain the phenomenon of immune exclusion in a subset of cancers. Increasing evidence has also shown that tumor-intrinsic signaling plays a key role in regulating the immunosuppressive tumor microenvironment and tumor immune escape. Therefore, understanding the mechanisms underlying immune avoidance mediated by tumor-intrinsic signaling may help identify new therapeutic targets for expanding the efficacy of cancer immunotherapies.

Regulation of PD-1/PD-L1 Pathway in Cancer by Noncoding RNAs

Immune checkpoint blockade has demonstrated significant anti-tumor immunity in an array of cancer types, yet the underlying regulatory mechanism of it is still obscure, and many problems remain to be solved. As an inhibitory costimulatory signal of T-cells, the programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway can paralyze T-cells at the tumor site, enabling the immune escape of tumor cells. Although many antibodies targeting PD-1/PD-L1 have been developed to block their interaction for the treatment of cancer, the reduced response rate and resistance to the therapies call for further comprehension of this pathway in the tumor microenvironment. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are two main types of noncoding RNAs that play critical parts in the regulation of immune response in tumorigenesis, including the PD-1/PD-L1 pathway. Here we summarize the most recent studies on the control of this pathway by noncoding RNAs in cancer and hopefully will offer new insights into immune checkpoint blockade therapies.

Epithelial cell plasticity defines heterogeneity in lung cancer

Lung cancer is the leading cause of cancer death for both men and women and accounts for almost 18.4% of all deaths due to cancer worldwide, with the global incidence increasing by approximately 0.5% per year. Lung cancer is regarded as a devastating type of cancer owing to its high prevalence, reduction in the health-related quality of life, frequently delayed diagnosis, low response rate, high toxicity, and resistance to available therapeutic options. The highly heterogeneous nature of this cancer with a proximal-to-distal distribution throughout the respiratory tract dramatically affects its diagnostic and therapeutic management. The diverse composition and plasticity of lung epithelial cells across the respiratory tract are regarded as significant factors underlying lung cancer heterogeneity. Therefore, definitions of the cells of origin for different types of lung cancer are urgently needed to understand lung cancer biology and to achieve early diagnosis and develop cell-targeted therapies. In the present review, we will discuss the current understanding of the cellular and molecular alterations in distinct lung epithelial cells that result in each type of lung cancer.

Mechanisms Controlling PD-L1 Expression in Cancer

The engagement of programmed cell death protein 1 (PD-1; encoded by the PDCD1 gene) receptor expressed on activated T cells and its ligand, programmed death-ligand 1 (PD-L1; encoded by the CD274 gene), is a major co-inhibitory checkpoint signaling that controls T cell activities. Various types of cancers express high levels of PD-L1 and exploit PD-L1/PD-1 signaling to evade T cell immunity. Blocking the PD-L1/PD-1 pathway has consistently shown remarkable anti-tumor effects in patients with advanced cancers and is recognized as the gold standard for developing new immune checkpoint blockade (ICB) and combination therapies. However, the response rates of anti-PD-L1 have been limited in several solid tumors. Therefore, furthering our understanding of the regulatory mechanisms of PD-L1 can bring substantial benefits to patients with cancer by improving the efficacy of current PD-L1/PD-1 blockade or other ICBs. In this review, we provide current knowledge of PD-L1 regulatory mechanisms at the transcriptional, posttranscriptional, post-translational, and extracellular levels, and discuss the implications of these findings in cancer diagnosis and immunotherapy.

Current concepts of non-coding RNA regulation of immune checkpoints in cancer

The discovery of immune checkpoint molecules as important regulators of immune responses in healthy individuals as well as immune escape of malignant tumours has led to profound changes in understanding, research and treatment of human cancer. Especially the introduction of immune checkpoint inhibitors in cancer therapy has set anti-cancer therapy on a novel level. With increasing experience of approved CTLA-4 and PD1/PD-L1 inhibitors and the evolution of novel immune checkpoint molecules from pre-clinical models to clinical trials, mechanisms of the regulation of these immune system guiding factors, are of paramount importance to overcome mechanisms of resistance. Non-protein coding RNAs (i.e. non-coding RNAs) such as short microRNAs and long non-coding RNAs are involved in regulating of various cellular processes and have attracted attention of cancer researchers and immunologists over the last years. In the present review, interactions between non coding RNAs and immune checkpoint molecules, within the framework of human cancer, will be discussed and current and developing concepts between the immunological and non-coding RNA world, will be elucidated.

Targeting the "undruggable" RAS - new strategies - new hope?

K-RAS is the most frequently mutated oncogene in solid tumors, such as pancreatic, colon or lung cancer. The GTPase K-RAS can either be in an active (GTP-loaded) or inactive (GDP-loaded) form. In its active form K-RAS forwards signals from growth factors, cytokines or hormones to the nucleus, regulating essential pathways, such as cell proliferation and differentiation. In turn, activating somatic mutations of this proto-oncogene deregulate the complex interplay between GAP (GTPase-activating) - and GEF (Guanine nucleotide exchange factor) - proteins, driving neoplastic transformation. Due to a rather shallow surface, K-RAS lacks proper binding pockets for small molecules, hindering drug development over the past thirty years. This review summarizes recent progress in the development of low molecular antagonists and further shows insights of a newly described interaction between mutant K-RAS signaling and PD-L1 induced immunosuppression, giving new hope for future treatments of K-RAS mutated cancer.

Impaired Tumor-Infiltrating T Cells in Patients with Chronic Obstructive Pulmonary Disease Impact Lung Cancer Response to PD-1 Blockade

RATIONALE

Patients with chronic obstructive pulmonary disease (COPD) have a higher prevalence of lung cancer. The chronic inflammation associated with COPD probably promotes the earliest stages of carcinogenesis. However, once tumors have progressed to malignancy, the impact of COPD on the tumor immune microenvironment remains poorly defined, and its effects on immune-checkpoint blockers' efficacy are still unknown.

OBJECTIVES

To study the impact of COPD on the immune contexture of non-small cell lung cancer.

METHODS

We performed in-depth immune profiling of lung tumors by immunohistochemistry and we determined its impact on patient survival (n = 435). Tumor-infiltrating T lymphocyte (TIL) exhaustion by flow cytometry (n = 50) was also investigated. The effectiveness of an anti-PD-1 (programmed cell death-1) treatment (nivolumab) was evaluated in 39 patients with advanced-stage non-small cell lung cancer. All data were analyzed according to patient COPD status.

MEASUREMENTS AND MAIN RESULTS

Remarkably, COPD severity is positively correlated with the coexpression of PD-1/TIM-3 (T-cell immunoglobulin and mucin domain-containing molecule-3) by CD8 T cells. In agreement, we observed a loss of CD8 T cell-associated favorable clinical outcome in COPD⁺ patients. Interestingly, a negative prognostic value of PD-L1 (programmed cell death ligand 1) expression by tumor cells was observed only in highly CD8 T cell-infiltrated tumors of COPD⁺ patients. Finally, data obtained on 39 patients with advanced-stage non-small cell lung cancer treated by an anti-PD-1 antibody showed longer progression-free survival in COPD⁺ patients, and also that the association between the severity of smoking and the response to nivolumab was preferentially observed in COPD⁺ patients.

CONCLUSIONS

COPD is associated with an increased sensitivity of CD8 tumor-infiltrating T lymphocytes to immune escape mechanisms developed by tumors, thus suggesting a higher sensitivity to PD-1 blockade in patients with COPD.

PTEN Alterations as a Potential Mechanism for Tumor Cell Escape from PD-1/PD-L1 Inhibition

The recent approval of immune checkpoint inhibitors drastically changed the standard treatments in many advanced cancer patients, but molecular changes within the tumor can prevent the activity of immunotherapy drugs. Thus, the introduction of the inhibitors of the immune checkpoint programmed death-1/programmed death ligand-1 (PD-1/PD-L1), should prompt deeper studies on resistance mechanisms, which can be caused by oncogenic mutations detected in cancer cells. PTEN, a tumor suppressor gene, dephosphorylates the lipid signaling intermediate PIP₃ with inhibition of AKT activity, one of the main effectors of the PI3K signaling axis. As a consequence of genetic or epigenetic aberrations, PTEN expression is often altered, with increased activation of PI3K axis. Interestingly, some data confirmed that loss of PTEN expression modified the pattern of cytokine secretion creating an immune-suppressive microenvironment with increase of immune cell populations that can promote tumor progression. Moreover, PTEN loss may be ascribed to reduction of tumor infiltrating lymphocytes (TILs), which can explain the absence of activity of immune checkpoint inhibitors. This review describes the role of PTEN loss as a mechanism responsible for resistance to anti PD-1/PD-L1 treatment. Moreover, combinatorial strategies between PD-1/PD-L1 inhibitors and PI3K/AKT targeting drugs are proposed as a new strategy to overcome resistance to immune checkpoint inhibition.

The AMPK-Related Kinases SIK1 and SIK3 Mediate Key Tumor-Suppressive Effects of LKB1 in NSCLC

Mutations in the LKB1 (also known as STK11) tumor suppressor are the third most frequent genetic alteration in non-small cell lung cancer (NSCLC). LKB1 encodes a serine/threonine kinase that directly phosphorylates and activates 14 AMPK family kinases ("AMPKRs"). The function of many of the AMPKRs remains obscure, and which are most critical to the tumor-suppressive function of LKB1 remains unknown. Here, we combine CRISPR and genetic analysis of the AMPKR family in NSCLC cell lines and mouse models, revealing a surprising critical role for the SIK subfamily. Conditional genetic loss of Sik1 revealed increased tumor growth in mouse models of Kras-dependent lung cancer, which was further enhanced by loss of the related kinase Sik3. As most known substrates of the SIKs control transcription, gene-expression analysis was performed, revealing upregulation of AP1 and IL6 signaling in common between LKB1- and SIK1/3-deficient tumors. The SIK substrate CRTC2 was required for this effect, as well as for proliferation benefits from SIK loss. SIGNIFICANCE: The tumor suppressor LKB1/STK11 encodes a serine/threonine kinase frequently inactivated in NSCLC. LKB1 activates 14 downstream kinases in the AMPK family controlling growth and metabolism, although which kinases are critical for LKB1 tumor-suppressor function has remained an enigma. Here we unexpectedly found that two understudied kinases, SIK1 and SIK3, are critical targets in lung cancer.This article is highlighted in the In This Issue feature, p. 1469.

Metformin as an archetype immuno-metabolic adjuvant for cancer immunotherapy

The development of a single immuno-metabolic adjuvant capable of modulating, in the appropriate direction and intensity, the complex antagonistic and symbiotic interplays between tumor cells, immune cells, and the gut microbiota may appear pharmacologically implausible. Metformin might help solve this conundrum and beneficially impact the state of cancer-immune system interactions.

Dysregulated Tgfbr2/ERK-Smad4/SOX2 Signaling Promotes Lung Squamous Cell Carcinoma Formation

Lung squamous cell carcinoma (SCC) is a common type of lung cancer. There is limited information on the genes and pathways that initiate lung SCC. Here, we report that loss of TGFβ type II receptor (Tgfbr2), frequently deleted in human lung cancer, led to predominant lung SCC development in Kras^G12D mice with a short latency, high penetrance, and extensive metastases. Tgfbr2-loss-driven lung SCCs resembled the salient features of human lung SCC, including histopathology, inflammatory microenvironment, and biomarker expression. Surprisingly, loss of Smad4, a key mediator of Tgfbr2, failed to drive lung SCC; instead, low levels of phosphorylated ERK1/2, a Smad-independent downstream effector of Tgfbr2, were tightly associated with lung SCC in both mouse and human. Mechanistically, inhibition of phosphorylated ERK1/2 significantly upregulated the expression of SOX2, an oncogenic driver of lung SCC, and cooperated with SMAD4 repression to elevate SOX2. Inhibition of ERK1/2 in Smad4^fl/fl ;Kras^G12D mice led to extensive lung SCC formation that resembled the SCC phenotype of Tgfbr2-deficient mice. Overall, we reveal a key role of ERK1/2 in suppressing SCC formation and demonstrate that dysregulated Tgfbr2/ERK-Smad4/SOX2 signaling drives lung SCC formation. We also present a mouse model of metastatic lung SCC that may be valuable for screening therapeutic targets. SIGNIFICANCE: This study sheds new light on the mechanisms underlying lung SCC formation driven by mutated Kras.

Recent Findings in the Regulation of Programmed Death Ligand 1 Expression

With the recent approvals for the application of monoclonal antibodies that target the well-characterized immune checkpoints, immune therapy shows great potential against both solid and hematologic tumors. The use of these therapeutic monoclonal antibodies elicits inspiring clinical results with durable objective responses and improvements in overall survival. Agents targeting programmed cell death protein 1 (PD-1; also known as PDCD1) and its ligand (PD-L1) achieve a great success in immune checkpoints therapy. However, the majority of patients fail to respond to PD-1/PD-L1 axis inhibitors. Expression of PD-L1 on the membrane of tumor and immune cells has been shown to be associated with enhanced objective response rates to PD-1/PD-L1 inhibition. Thus, an improved understanding of how PD-L1 expression is regulated will enable us to better define its role as a predictive marker. In this review, we summarize recent findings in the regulation of PD-L1 expression.

Cancer Stem Cells: Concepts, Challenges, and Opportunities for Cancer Therapy

Cancer stem cells (CSCs) are a subpopulation of cancer cells with self-renewal capacity, that fuel tumor growth and contribute to the heterogeneous nature of tumors. First identified in hematological malignancies, CSC populations have to date been proposed in solid tumors in various organs. In vitro and in vivo assays, mouse genetic models, and more recently single-cell sequencing technologies and other '-omics' methodologies have not only facilitated the identification of novel CSC populations but also revealed and clarified novel properties of CSCs. Increasingly, both cell-autonomous and CSC niche factors are recognized as important contributors of CSC properties. The deepened understanding of CSC properties and characteristics would enable and facilitate the rational design of CSC-specific therapeutics that would, ideally, have high selectivity for cancer cells, eliminate tumor bulk, and prevent tumor recurrence. Addressing these issues would form some of the key challenges of the CSC research field in the coming years.

Genomic ERBB2/ERBB3 mutations promote PD-L1-mediated immune escape in gallbladder cancer: a whole-exome sequencing analysis

OBJECTIVES

Patients with gallbladder carcinoma (GBC) lack effective treatment methods largely due to the inadequacy of both molecular characterisation and potential therapeutic targets. We previously uncovered a spectrum of genomic alterations and identified recurrent mutations in the ErbB pathway in GBC. Here, we aimed to study recurrent mutations of genes and pathways in a larger cohort of patients with GBC and investigate the potential mechanisms and clinical significance of these mutations.

DESIGN

We performed whole-exome sequencing (WES) in 157 patients with GBC. Functional experiments were applied in GBC cell lines to explore the oncogenic roles of ERBB2/ERBB3 hotspot mutations, their correlation with PD-L1 expression and the underlying mechanisms. ERBB inhibitors and a PD-L1 blocker were used to evaluate the anticancer activities in co-culture systems in vitro and in vivo.

RESULTS

WES identified ERBB2 and ERBB3 mutations at a frequency of 7%-8% in the expanded cohort, and patients with ERBB2/ERBB3 mutations exhibited poorer prognoses. A set of in vitro and in vivo experiments revealed increased proliferation/migration on ERBB2/ERBB3 mutation. Ectopic expression of ERBB2/ERBB3 mutants upregulated PD-L1 expression in GBC cells, effectively suppressed normal T-cell-mediated cytotoxicity in vitro through activation of the PI3K/Akt signalling pathway and contributed to the growth and progression of GBC in vivo. Treatment with an ERBB2/ERBB3 inhibitor or a PD-L1 monoclonal antibody reversed these immunosuppressive effects, and combined therapy revealed promising therapeutic activities.

CONCLUSIONS

ERBB2/ERBB3 mutations may serve as useful biomarkers in identifying patients who are sensitive to ERBB2/ERBB3 inhibitors and PD-L1 monoclonal antibody treatment.

TRIAL REGISTRATION NUMBER

NCT02442414;Pre-results.

Targeting the Interplay between Epithelial-to-Mesenchymal-Transition and the Immune System for Effective Immunotherapy

Over the last decade, both early diagnosis and targeted therapy have improved the survival rates of many cancer patients. Most recently, immunotherapy has revolutionized the treatment options for cancers such as melanoma. Unfortunately, a significant portion of cancers (including lung and breast cancers) do not respond to immunotherapy, and many of them develop resistance to chemotherapy. Molecular characterization of non-responsive cancers suggest that an embryonic program known as epithelial-mesenchymal transition (EMT), which is mostly latent in adults, can be activated under selective pressures, rendering these cancers resistant to chemo- and immunotherapies. EMT can also drive tumor metastases, which in turn also suppress the cancer-fighting activity of cytotoxic T cells that traffic into the tumor, causing immunotherapy to fail. In this review, we compare and contrast immunotherapy treatment options of non-small cell lung cancer (NSCLC) and triple negative breast cancer (TNBC). We discuss why, despite breakthrough progress in immunotherapy, attaining predictable outcomes in the clinic is mostly an unsolved problem for these tumors. Although these two cancer types appear different based upon their tissues of origin and molecular classification, gene expression indicate that they possess many similarities. Patient tumors exhibit activation of EMT, and resulting stem cell properties in both these cancer types associate with metastasis and resistance to existing cancer therapies. In addition, the EMT transition in both these cancers plays a crucial role in immunosuppression, which exacerbates treatment resistance. To improve cancer-related survival we need to understand and circumvent, the mechanisms through which these tumors become therapy resistant. In this review, we discuss new information and complementary perspectives to inform combination treatment strategies to expand and improve the anti-tumor responses of currently available clinical immune checkpoint inhibitors.

Paired genomic analysis of squamous cell carcinoma transformed from EGFR-mutated lung adenocarcinoma

OBJECTIVES

Adenocarcinoma (ADC) to squamous cell carcinoma (SCC) transformation (AST) is reported in epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer after tyrosine kinase inhibitor (TKI) failure. However, little is known about the underlying genomic changes during the AST process.

MATERIALS AND METHODS

We retrospectively reviewed our tissue database collected after first- or second- generation EGFR TKI resistance (n = 263) and identified 3 cases of AST. The additional case was acquired from the osimertinib resistance sample. Deep target sequencing (381 genes) using paired samples from 4 patients with AST after EGFR TKI treatment was performed. The histology of each sample was confirmed by TTF-1 and p63 immunohistochemistry. The patients received first- or second-generation EGFR TKI as an initial treatment.

RESULTS

Overall incidence of AST was 1.1% (3/263). Transformed SCC acquired genomic alterations related to the PI3K/AKT/mTOR pathway, in addition to the initial EGFR mutation. In a representative case, two separate sub-clones, with a PTEN nonsense mutation and EGFR p.T790 M mutation, were observed without histologic transformation at the time of gefitinib resistance. After subsequent treatment with osimertinib, SCC transformation was observed with the disappearance of the EGFR p.T790 M mutation and acquired copy number loss in PTEN. Adopting the sub-clonal fraction model elucidates the sub-clonal evolution process of the PTEN mutant sub-clone toward AST under the background of EGFR mutation. The rest of the transformed samples also had acquired genomic alterations in PTEN, LKB1, PIK3CA, or RICTOR, which are related to the PI3K/AKT/mTOR pathway.

CONCLUSIONS

Paired genomic analysis from our sample provides early clinical evidence of the ADC to SCC lineage transition that might be provoked by an alteration in the PI3K/AKT/mTOR pathway during EGFR TKI treatment. This finding could potentially broaden the known spectrum of EGFR TKI resistance mechanisms.

JNK1/2 represses Lkb1-deficiency-induced lung squamous cell carcinoma progression

Mechanisms of lung squamous cell carcinoma (LSCC) development are poorly understood. Here, we report that JNK1/2 activities attenuate Lkb1-deficiency-driven LSCC initiation and progression through repressing ΔNp63 signaling. In vivo Lkb1 ablation alone is sufficient to induce LSCC development by reducing MKK7 levels and JNK1/2 activities, independent of the AMPKα and mTOR pathways. JNK1/2 activities is positively regulated by MKK7 during LSCC development. Pharmaceutically elevated JNK1/2 activities abates Lkb1 dependent LSCC formation while compound mutations of Jnk1/2 and Lkb1 further accelerate LSCC progression. JNK1/2 is inactivated in a substantial proportion of human LSCC and JNK1/2 activities positively correlates with survival rates of lung, cervical and head and neck squamous cell carcinoma patients. These findings not only determine a suppressive role of the stress response regulators JNK1/2 on LSCC development by acting downstream of the key LSCC suppresser Lkb1, but also demonstrate activating JNK1/2 activities as a therapeutic approach against LSCC.

LKB1 is frequently mutated in lung squamous cell carcinomas. Here, the authors show that sole LKB1 depletion is sufficient to drive the development of this cancer, where downstream defective MKK7-JNK1/2 signalling activates the ∆Np63/p63 pathway to induce subsequent epithelial cells transformation and tumour progression.

Exosomal PD-L1 Retains Immunosuppressive Activity and is Associated with Gastric Cancer Prognosis

BACKGROUND

A recent study showed that circulating exosomal PD-L1 is an effective predictor for anti-PD-1 therapy in melanomas. Exosomal PD-L1 induced immunosuppression microenvironments in cancer patients. However, its prognostic value and immunosuppressive effect in gastric cancer (GC) were poorly understood.

METHODS

We retrospectively evaluated the prognostic value of exosomal PD-L1 and soluble PD-L1 in preoperative plasma of 69 GC patients. The correlation between exosomal PD-L1 and the T cell counts or cytokine in the plasma was evaluated in 31 metastatic GC patients before chemotherapy.

RESULTS

Overall survival (OS) was significantly lower in the high exosomal PD-L1 group compared with the low exosomal PD-L1 group (P = 0.004). Exosomal PD-L1 was an independent prognostic factor in GC (n = 69, 95% confidence interval = 1.142-7.669, P = 0.026). However, soluble PD-L1 showed no correlation with OS (P = 0.139). Additionally, exosomal PD-L1 in the plasma samples of 31 metastatic GC patients was negatively associated with CD4+ T cell count (P = 0.001, R = - 0.549), CD8+ T-cell count (P = 0.054, R = - 0.349), and granzyme B (P = 0.002, R = - 0.537), indicating that exosomal PD-L1 was associated with immunosuppressive status of GC patients. GC cells also secreted exosomal PD-L1 and were positively associated with the amount of PD-L1 in corresponding GC cell lines. Besides, exosomal PD-L1 significantly decreased T-cell surface CD69 and PD-1 expressions compared with soluble PD-L1 due to its stable and MHC-I expression.

CONCLUSIONS

Overall, exosomal PD-L1 predicts the worse survival and reflects the immune status in GC patients, resulting from a stronger T-cell dysfunction due to its stable and MHC-I expression.

Low CD8⁺ T Cell Infiltration and High PD-L1 Expression Are Associated with Level of CD44⁺/CD133⁺ Cancer Stem Cells and Predict an Unfavorable Prognosis in Pancreatic Cancer

Cancer immunotherapy targeting immune checkpoints has exhibited promising clinical outcomes in many cancers, but it offers only limited benefits for pancreatic cancer (PC). Cancer stem cells (CSCs), a minor subpopulation of cancer cells, play important roles in tumor initiation, progression, and drug resistance. Accumulating evidence suggests that CSCs employ immunosuppressive effects to evade immune system recognition. However, the clinical implications of the associations among CD8⁺ T cells infiltration, programmed death receptor ligand-1 (PD-L1) expression, and CSCs existence are poorly understood in PC. Immunostaining and quantitative analysis were performed to assess CD8⁺ T cells infiltration, PD-L1 expression, and their relationship with CD44⁺/CD133⁺ CSCs and disease progression in PC. CD8⁺ T cells infiltration was associated with better survival while PD-L1 expression was correlated with PC recurrence. Both the low CD8⁺ T cells infiltration/high PD-L1 expression group and the high CD8⁺ T cells infiltration/high PD-L1 expression group show high levels of CD44⁺/CD133⁺ CSCs, but patients with low CD8⁺ T cells infiltration/high PD-L1 expression had worse survival and higher recurrence risk than those with high CD8⁺ T cells infiltration/high PD-L1 expression. Moreover, high infiltration of CD8⁺ T cells could reduce unfavorable prognostic effect of high co-expression of PD-L1 and CD44/CD133. Our study highlights an interaction among CD8⁺ T cells infiltration, PD-L1 expression, and CD44⁺/CD133⁺ CSCs existence, which contributes to PC progression and immune evasion.

Recent advances of therapeutic targets based on the molecular signature in breast cancer: genetic mutations and implications for current treatment paradigms

Breast cancer is the most common malignancy in women all over the world. Genetic background of women contributes to her risk of having breast cancer. Certain inherited DNA mutations can dramatically increase the risk of developing certain cancers and are responsible for many of the cancers that run in some families. Regarding the widespread multigene panels, whole exome sequencing is capable of providing the evaluation of genetic function mutations for development novel strategy in clinical trials. Targeting the mutant proteins involved in breast cancer can be an effective therapeutic approach for developing novel drugs. This systematic review discusses gene mutations linked to breast cancer, focusing on signaling pathways that are being targeted with investigational therapeutic strategies, where clinical trials could be potentially initiated in the future are being highlighted.

Immunologic Targeting of Cancer Stem Cells

Cancer stem cells (CSCs) are crucial for tumor recurrence and distant metastasis. Immunologically targeting CSCs represents a promising strategy to improve efficacy of multimodal cancer therapy. Modulating the innate immune response involving Toll-like receptors, macrophages, natural killer cells, and γδT cells has therapeutic effects on CSCs. Antigens expressed by CSCs provide specific targets for immunotherapy. CSC-primed dendritic cell-based vaccines have induced significant antitumor immunity as an adjuvant therapy in experimental models of established tumors. Targeting the tumor microenvironment CSC niche with cytokines or checkpoint blockade provides additional strategies to eliminate CSCs.