Oncogenic RAS Signaling Promotes Tumor Immunoresistance by Stabilizing PD-L1 mRNA

Drugging the Undruggable and beyond: Emerging precision oncology approaches to target acquired resistance to KRAS G12C and KRAS G12D inhibitors

Development of mutant specific KRAS inhibitors validated KRAS as a 'druggable' target. However, excellent initial efficacy was eventually overshadowed by failure to exhibit sustained clinical response, primarily due to acquired resistance. Some targeted therapies like SOS1, SHP2, and MEK inhibitors, in combination with mutant KRAS G12C inhibitors (G12Ci), are currently under clinical investigation with evidences of improving efficacy. However, a deep understanding of the underlying molecular pathways behind the acquired resistance is still at a nascent stage. Recent preclinical studies have uncovered a role of novel proteins and pathways responsible for resistance and their inhibition demonstrated a robust anticancer efficacy in combination. Plethora of combination therapy approaches are now being proposed with emergence of AXL, ULK1, Tissue factor, farnesyltransferase, etc. as targets to counter G12Ci resistance. This review summarizes in a comprehensive manner, some of the novel combination modalities to overcome G12Ci resistance, based on current understanding and with great potential to hit clinical success. Along with G12C, KRAS G12D (G12D) was also considered a formidable foe, until the discovery of selective inhibitors. However, eventual clinical resistance can eclipse the early success and requires an in-depth understanding of resistance mechanisms. Evidences of G12Ci resistance can be exploited as probable combination strategies to tackle ensuing resistance to G12D inhibitors (G12Di), and can translate in superior clinical efficacy. Early preclinical studies of G12Di in combination with ERBB, SOS1, AKT and immune-checkpoints inhibitors indicate encouraging response. This review further describes some of the early affirmations on combination strategies with G12Di. We postulate to go beyond 'Drugging the Undruggable' with advanced combination approaches mitigating G12C and G12D inhibitor resistance.

Pan-HDAC inhibitor LAQ824 inhibits the progression of pancreatic ductal adenocarcinoma and suppresses immune escape by promoting antigen presentation

Pancreatic cancer is the seventh leading cause of cancer-related deaths worldwide, with a dismal 5-year survival rate. New drugs targeting pancreatic ductal adenocarcinoma (PDAC), the primary pathological subtype, are urgently needed. LAQ824, a novel pan-histone deacetylase inhibitor (HDACi), has shown anti-tumor activity in various cancers, but its effects on PDAC remain unexplored. This study investigates the therapeutic potential of LAQ824 in PDAC and its role in modulating immune escape mechanisms. Using a subcutaneous tumor model in C57BL/6 J mice, LAQ824's anti-tumor effects were evaluated. In vitro and in vivo experiments-including IHC, flow cytometry, RNA sequencing, and single-cell RNA sequencing-demonstrated that LAQ824 inhibits tumor proliferation, suppresses the epithelial-mesenchymal transition (EMT), and induces apoptosis. LAQ824 also enhances immunogenicity by upregulating MHC-I-mediated antigen presentation, increasing immune cell infiltration, and promoting CD8+ T cell maturation and differentiation. Mechanistically, LAQ824 upregulated MHC-I expression by enhancing chromatin accessibility of related genes, with HDAC1 identified as a key repressor of MHC-I in PDAC cells. In conclusion, we found that LAQ824 has a significant anti-tumor effect in PDAC. LAQ824 not only directly affects general biological behaviors such as proliferation, apoptosis, and EMT, but also increases the immunogenicity of tumor cells by upregulating the expression of MHC-I in PDAC, which promotes the antigen presentation process and enhances anti-tumor immunity. By showcasing LAQ824's potential as a therapeutic target against PDAC, the present study provides novel insights into the link between epigenetic regulation and immunogenicity in PDAC.

ZFP36-family RNA-binding proteins in regulatory T cells reinforce immune homeostasis

RNA binding proteins (RBP) of the ZFP36 family limit the differentiation and effector functions of CD4 and CD8 T cells, but little is known of their expression or function in regulatory T (Treg) cells. By using Treg cell-restricted deletion of Zfp36 family members we identify the role of Zfp36l1 and Zfp36l2 in Treg cells to maintain immune homeostasis. Mice with Treg cells deficient in these RBP display an inflammatory phenotype with an expansion in the numbers of type-2 conventional dendritic cells, T effector cells, T follicular helper and germinal center B cells and elevated serum cytokines and immunoglobulins. In the absence of Zfp36l1 and Zfp36l2, the pool of cycling CTLA-4 in naïve Treg cells is reduced, Treg cells are less sensitive to IL-2 and IL-7 but are more sensitive to IFNγ. In mice lacking both RBP in Treg cells, the deletion of a single allele of Ifng is sufficient to ameliorate the pathology. Our results indicate that ZFP36L1 and ZFP36L2 regulate the availability of IFNγ and are required for the maintenance of Treg cell stability. Thus, ZFP36L1 and ZFP36L2 regulate multiple pathways that enable Treg cells to enforce immune homeostasis.

H3K27me3-mediated regulation of PD-L1 expression in triple-negative breast cancer (TNBC)

PURPOSE

Enhancer of zeste homolog 2 (EZH2) is highly expressed in triple-negative breast cancer (TNBC) and induces massive histone modification via trimethylation at lysine 27 of histone H3 (H3K27me3). The expression level of programmed death ligand 1 (PD-L1) is crucial for determining the indications for immune checkpoint inhibitors in patients with TNBC. This study aimed to clarify the regulatory roles of EZH2 and H3K27me3 in the PD-L1 expression in TNBC cells.

METHODS

The change in the expression of PD-L1 at mRNA and protein levels was investigated by establishing an EZH2-knockdown MDA-MB-231 cell line using siRNA followed by RT-qPCR and western blotting analyses. Localization of the PD-L1 protein was assessed using immunofluorescence. Chromatin immunoprecipitation (ChIP) assays were performed to investigate the histone methylation status of PD-L1 promoter regions. The correlation among PD-L1, EZH2, and H3K27me3 protein expressions was explored in 57 patients with TNBC through immunohistochemistry.

RESULTS

Knockdown of EZH2 restored the PD-L1 expression and localization of PD-L1 protein in the cellular membrane. ChIP assay revealed that the knockdown of EZH2 diminished H3K27 trimethylation and enhanced H3K4 trimethylation in the promoter region of PD-L1. Immunohistochemical analysis of TNBC specimens reflected an inverse correlation between PD-L1 expression and H3K27me3 nuclear positivity; however, no correlation between H3K27me3 status and EZH2 expression was observed.

CONCLUSIONS

The downregulation of EZH2 can potentially enhance the efficacy of immune checkpoint inhibitors in patients with TNBC and may provide a new therapeutic strategy.

Thyroid dysfunction as a predictor of PD- 1/PD-L1 inhibitor efficacy in advanced lung cancer

PURPOSE

To investigate the correlation between thyroid dysfunction (TD) and the efficacy of programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) inhibitors in the treatment of advanced lung cancer, and the possible influencing factors for TD occurrence, providing insights that could guide individualized therapeutic approaches.

METHODS

The data of 120 advanced lung cancer patients from January 2019 to August 2024 were retrospectively collected. Then, the patients were divided into TD and non-TD subgroups according to whether TD occurred or not, to analyse the possible factors influencing the occurrence of TD and the correlation between TD and PD-1/PD-L1 inhibitor efficacy.

RESULTS

For all cases, the baseline TSH level was significantly higher in the TD subgroup than in the non-TD subgroup (median: 2.33 mIU/L vs. 1.58 mIU/L, p = 0.001). The progression-free survival (PFS) was significantly longer in the TD subgroup than in the non-TD subgroup (mPFS: 7.90 months vs. 4.87 months, p = 0.003), and the patients in the TD subgroup had a lower HR for progression (0.499, 95% CI (0.317-0.766)). For the PD-1/PD-L1 inhibitor group, the baseline TSH level was also significantly higher in the TD subgroup than in the non-TD subgroup (median: 2.16 mIU/L vs. 1.52 mIU/L, p = 0.009). The PFS was also significantly longer in the TD subgroup than in the non-TD subgroup (mPFS: 8.83 months vs. 6.50 months, p = 0.041).

CONCLUSIONS

The baseline TSH level was the predictive factor for the occurrence of TD. The occurrence of TD was positively associated with a favorable prognosis for patients with advanced lung cancer.

Recent Progress and Potential of G4 Ligands in Cancer Immunotherapy

G-quadruplex (G4) structures are non-canonical nucleic acid conformations that play crucial roles in gene regulation, DNA replication, and telomere maintenance. Recent studies have highlighted G4 ligands as promising anticancer agents due to their ability to modulate oncogene expression and induce DNA damage. By stabilizing G4 structures, these ligands affect tumor progression. Additionally, they have been implicated in tumor immunity modulation, particularly through the activation and immunogenic cell death induction of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway. Moreover, their disruption of telomere maintenance and regulation of key oncogenes, such as c-MYC and KRAS, position them as candidates for immune-based therapeutic interventions. Despite their therapeutic potential, challenges remain in optimizing their clinical applications, particularly in patient stratification and elucidating their immunomodulatory effects. This review provides a comprehensive overview of the mechanisms through which G4 ligands influence tumor progression and immune regulation, highlighting their potential role in future cancer immunotherapy strategies.

Current status of KRAS G12C inhibitors in NSCLC and the potential for combination with anti-PD-(L)1 therapy: a systematic review

In recent years, precision medicine for non-small cell lung cancer (NSCLC) has made significant strides, particularly with advancements in diagnostic and therapeutic technologies. Targeted 7therapies and Anti-PD-(L)1 Therapies have emerged as vital treatment options, yet KRAS mutations, especially KRAS G12C, have been historically difficult to address. Due to the unique activation mechanism of KRAS G12C has led to the development of specific inhibitors, such as AMG 510 and MRTX849, which show promising therapeutic potential. However, results from the CodeBreaK 200 Phase III trial indicated that AMG 510 did not significantly improve overall survival compared to docetaxel. Resistance after prolonged use of KRAS G12C inhibitors continues to pose a challenge, prompting interest in new drugs and combination strategies. KRAS mutations can impair tumor-infiltrating T cell function and create an immunosuppressive tumor microenvironment, making the combination of KRAS G12C inhibitors with anti-PD-(L)1 therapies particularly appealing. Preliminary data suggest these combinations may enhance both survival and quality of life, though safety concerns remain a barrier. Ongoing research is crucial to refine treatment regimens and identify suitable patient populations. This review focuses on the development of KRAS G12C inhibitors in monotherapy and combination therapies for NSCLC, discussing major clinical trials and future research directions.

Senescence-induced p21high macrophages contributed to CD8+ T cells-related immune hyporesponsiveness in kidney transplantation via Zfp36/IL-27 axis

Recipients' age has emerged as a key factor that impacts on acute renal allograft rejection and graft survival. Age-related functional and structural changes in the immune system have been observed, yet the precise influence of aged immunity on kidney transplant remains unclear. In an initial retrospective analysis of clinical data gathered from two major centers in China and Germany, we found a correlation between aging and mitigated rejection outcomes in kidney recipients. To study the mechanism, we performed kidney transplantation on mice and observed attenuated allograft rejection in senescent recipients. Single-cell transcriptome analysis of allograft kidneys indicated a protective role of p21high macrophages in aged mice. Supernatant collected from p21high macrophage primary culture inhibited the cytotoxic function and proliferation of CD8+ T cells. Zfp36 is highly expressed in senescent p21high macrophages. To determine its role in renal allograft rejection, we studied mice with Zfp36 conditionally deleted in macrophages (Zfp36-cKO). These mice developed exacerbated allograft rejection with enhanced IL-27 production and CD8+ T cell hyperactivation. Inhibition of IL-27 with neutralizing antibody or deletion of IL-27 receptor on CD8+ T cells reversed acute renal allograft rejection in Zfp36-cKO mice. Moreover, in vitro silencing Zfp36 with siRNA led to impaired degradation of IL-27 p28 mRNA and a subsequent increase of IL-27 in p21high macrophages. In conclusion, senescent macrophages protect renal allograft rejection by suppressing CD8+ T cells via a Zfp36/IL-27-dependent mechanism. These findings may provide innovative therapeutic strategies for addressing kidney allograft rejection.

Immune-Based Strategies for Pancreatic Cancer in the Adjuvant Setting

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related mortality in the United States, with poor overall survival across all stages. Less than 20% of patients are eligible for curative surgical resection at diagnosis, and despite adjuvant chemotherapy, most will experience disease recurrence within two years. The incorporation of immune-based strategies in the adjuvant setting remains an area of intense investigation with unrealized promise. It offers the potential of providing durable disease control for micro-metastatic disease following curative intent surgery and enabling personalized treatments based on mutational neoantigen profiles derived from resected specimens. However, most of these attempts have failed to demonstrate significant clinical success, likely due to the immunosuppressive tumor microenvironment (TME) and individual genetic heterogeneity. Despite these challenges, immune-based strategies, such as therapeutic vaccines targeted towards neoantigens, have demonstrated promise via immune activation and induction of T-cell tumor infiltration. In this review, we will highlight the foundational lessons learned from previous clinical trials of adjuvant immunotherapy, discussing the knowledge gained from analyses of trials with disappointing results. In addition, we will discuss how these data have been incorporated to design new agents and study concepts that are proving to be exciting in more recent trials, such as shared antigen vaccines and combination therapy with immune-checkpoint inhibitors and chemotherapy. This review will evaluate novel approaches in ongoing and future clinical studies and provide insight into how these immune-based strategies might evolve to address the unique challenges for treatment of PDAC in the adjuvant setting.

Genomics guiding personalized first-line immunotherapy response in lung and bladder tumors

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment, particularly in advanced non-small cell lung cancer (NSCLC) and muscle-invasive bladder cancer (MIBC). However, identifying reliable predictive biomarkers for ICI response remains a significant challenge. In this study, we analyzed real-world cohorts of advanced NSCLC and MIBC patients treated with ICI as first-line therapy.

METHODS

Tumor samples underwent Whole Genome Sequencing (WGS) to identify specific somatic variants and assess tumor mutational burden (TMB). Additionally, mutational signature extraction and pathway enrichment analyses were performed to uncover the underlying mechanisms of ICI response. We also characterized HLA-I haplotypes and investigated LINE-1 retrotransposition.

RESULTS

Distinct mutation patterns were identified in patients who responded to treatment, suggesting potential biomarkers for predicting ICI effectiveness. In NSCLC, tumor mutational burden (TMB) did not differ significantly between responders and non-responders, while in MIBC, higher TMB was linked to better responses. Specific mutational signatures and HLA haplotypes were associated with ICI response in both cancers. Pathway analysis showed that NSCLC responders had active inflammatory and immune pathways, while pathways enriched in non-responders related to FGFR3 and neural crest differentiation, associated to resistance mechanisms. In MIBC, responders had alterations in DNA repair, leading to more neoantigens and a stronger ICI response. Importantly, for the first time, we found that LINE-1 activation was positively linked to ICI response, especially in MIBC.

CONCLUSION

These findings reveal promising biomarkers and mechanistic insights, offering a new perspective on predicting ICI response and opening up exciting possibilities for more personalized immunotherapy strategies in NSCLC and MIBC.

IMPDH inhibitors upregulate PD-L1 in cancer cells without impairing immune checkpoint inhibitor efficacy

Tumor cells are characterized by rapid proliferation. In order to provide purines for DNA and RNA synthesis, inosine 5'-monophosphate dehydrogenase (IMPDH), a key enzyme in the de novo guanosine biosynthesis, is highly expressed in tumor cells. In this study we investigated whether IMPDH was involved in cancer immunoregulation. We revealed that the IMPDH inhibitors AVN944, MPA or ribavirin concentration-dependently upregulated PD-L1 expression in non-small cell lung cancer cell line NCI-H292. This effect was reproduced in other non-small cell lung cancer cell lines H460, H1299 and HCC827, colon cancer cell lines HT29, RKO and HCT116, as well as kidney cancer cell line Huh7. In NCI-H292 cells, we clarified that IMPDH inhibitors increased CD274 mRNA levels by enhancing CD274 mRNA stability. IMPDH inhibitors improved the affinity of the ARE-binding protein HuR for CD274 mRNA, thereby stabilizing CD274 mRNA. Guanosine supplementation abolished the IMPDH inhibitor-induced increase in PD-L1 expression. In CT26 and EMT6 tumor models used for ICIs based studies, we showed that despite its immunosuppressive properties, the IMPDH inhibitor mycophenolate mofetil did not reduce the clinical response of checkpoint inhibitors, representing an important clinical observation given that this class of drugs is approved for use in multiple diseases. We conclude that PD-L1 induction contributes to the immunosuppressive effect of IMPDH inhibitors. Furthermore, the IMPDH inhibitor mycophenolate mofetil does not antagonize immune checkpoint blockade.

The NF1 tumor suppressor regulates PD-L1 and immune evasion in melanoma

Hotspot BRAF, hotspot NRAS, and NF1 loss-of-function mutations are found in approximately 50%, 25%, and 15% of cutaneous melanomas, respectively. Compared to mutant BRAF and NRAS, the role of NF1 loss in melanoma remains understudied. NF1 has a RAS GTPase-activating protein (GAP) function; however, studies also support NF1 RAS-independent tumor-suppressor functions. Recent reports indicate that patients with NF1 mutant melanoma have high response rates to anti-PD-1 immune checkpoint inhibitors (ICIs) for reasons that are not entirely clear. Here, we present data demonstrating that NF1 interacts with PD-L1. Furthermore, NF1 loss in melanoma lines increases PD-L1 cell surface expression through a RAS-GAP-independent mechanism. Co-culture experiments demonstrate that NF1 depletion in melanoma increases resistance to T cell killing, which can be abrogated with anti-PD-1/PD-L1 ICIs. These results support a model whereby NF1 loss leads to immune evasion through the PD-L1/PD-1 axis, providing support for the examination of anti-PD-1 therapies in other NF1 mutant cancers.

Pancreatic cancer: failures and hopes-a review of new promising treatment approaches

Pancreatic cancer is a challenging disease with limited treatment options and a high mortality rate. Just few therapy advances have been made in recent years. Tumor microenvironment, immunosuppressive features and mutational status represent important obstacles in the improvement of survival outcomes. Up to now, first-line therapy did achieve a median overall survival of less than 12 months and this discouraging data lead clinicians all over the world to focus their efforts on various fields of investigation: 1) sequential cycling of different systemic therapy in order to overcome mechanisms of resistance; 2) discovery of new predictive bio-markers, in order to target specific patient population; 3) combination treatment, in order to modulate the tumor microenvironment of pancreatic cancer; 4) new modalities of the delivery of drugs in order to pass the physical barrier of desmoplasia and tumor stroma. This review shows future directions of treatment strategies in advanced pancreatic cancer through a deep analysis of these recent macro areas of research.

SOS1 inhibitor BI-3406 shows in vivo antitumor activity akin to genetic ablation and synergizes with a KRASG12D inhibitor in KRAS LUAD

We evaluated the in vivo therapeutic efficacy and tolerability of BI-3406-mediated pharmacological inhibition of SOS1 in comparison to genetic ablation of this universal Ras-GEF in various KRAS-dependent experimental tumor settings. Contrary to the rapid lethality caused by SOS1 genetic ablation in SOS2KO mice, SOS1 pharmacological inhibition by its specific inhibitor BI-3406 did not significantly affect animal weight/viability nor cause noteworthy systemic toxicity. Allograft assays using different KRASmut cell lines showed that treatment with BI-3406 impaired RAS activation and RAS downstream signaling and decreased tumor burden and disease progression as a result of both tumor-intrinsic and -extrinsic therapeutic effects of the drug. Consistent with prior genetic evidence and the KRASmut allografts assays in immunocompromised mice, our analyses using an in vivo model of KRASG12D-driven lung adenocarcinoma (LUAD) in immunocompetent mice showed that single, systemic BI-3406 treatment impaired tumor growth and downmodulated protumorigenic components of the tumor microenvironment comparably to SOS1 genetic ablation or to treatment with the specific KRASG12D inhibitor MRTX1133. Furthermore, markedly stronger, synergistic antitumor effects were observed upon concomitant treatment with BI-3406 and MRTX1133 in the same in vivo LUAD mouse model. Our data confirm SOS1 as an actionable therapy target in RAS-dependent cancers and suggest that BI-3406 treatment may yield clinical benefit both as monotherapy or as a potential combination partner for multiple RAS-targeting strategies.

Itaconate targets the ERK2 signal to suppress estrogen receptor-positive breast cancer cell growth

Over 70% of breast cancers are estrogen receptor (ER)-positive, with Tamoxifen (Tam) being a standard treatment. However, around 40% of these cancers develop resistance to Tam, which poses a significant clinical challenge. The ACOD1/itaconate (ITA) axis, a metabolic pathway that produces itaconate, has shown promise in inhibiting the growth of ER-positive breast cancer cells. Nonetheless, it remains unclear how effective ITA is against Tam-resistant breast cancer cells and the underlying mechanisms involved. The current report found that Tam-resistant cells exhibit increased sensitivity to ITA compared to their parental cells and show a synergetic effect in combination treatment with Tam. An unbiased proteomic analysis revealed that upregulating the ERK2 signaling pathway contributes to the sensitivity of ER-positive breast cancer cells to ITA. ITA treatment increases ERK2 phosphorylation at T185/Y187 sites by directly alkylating cysteine 254, leading to ERK2 activation and subsequent cell growth inhibition. These effects were abolished in ITA allylation-resistant cells when a cysteine residue was replaced with serine. Additionally, itaconate-induced ERK2 phosphorylation and activation inhibits the growth of Tam-resistant breast cancer cells, which effect is advanced in phosphorylation-mimic ERK2_T185E-expressing cells but blocked in those expressing non-phosphorylation-mimic ERK2_T185A. Furthermore, activated ERK2 interacts physically with API5 to disrupt API5's localization to the nucleus speckle, where API5 may interact with other molecules critical in regulating cell growth-related genes. Our findings clarify the mechanism through which ITA exerts its effects on tamoxifen-sensitive and resistant breast cancer cells and highlight the potential of itaconate as an alternative treatment strategy against breast cancer.

Immunotherapy in advanced, KRAS G12C-mutant non-small-cell lung cancer: current strategies and future directions

Kirsten rat sarcoma (KRAS) mutations are present in up to 25% of non-small-cell lung cancer (NSCLC). KRAS G12C is the most common type of mutation, representing approximately half of the cases in KRAS-mutant NSCLC. Mutations in KRAS activate the RAF-MEK-ERK pathway, leading to increased cell proliferation and survival. Recent advances in drug development have led to the approval of KRAS G12C inhibitors sotorasib and adagrasib. This review explores the emerging therapeutic strategies in KRAS G12C-mutant NSCLC, including dual checkpoint blockade and combinations with checkpoint inhibitors, with a focus on the setting of advanced disease.

A Pan-RAS Inhibitor with a Unique Mechanism of Action Blocks Tumor Growth and Induces Antitumor Immunity in Gastrointestinal Cancer

Activated RAS is a common driver of cancer that was considered undruggable for decades. Recent advances have enabled the development of RAS inhibitors, but the efficacy of these inhibitors remains limited by resistance. In this study, we developed a pan-RAS inhibitor, ADT-007, (Z)-2-(5-fluoro-1-(4-hydroxy-3,5-dimethoxybenzylidene)-2-methyl-1H-inden-3-yl)-N-(furan-2-ylmethyl)acetamide, that binds nucleotide-free RAS to block GTP activation of effector interactions and MAPK/AKT signaling, resulting in mitotic arrest and apoptosis. ADT-007 potently inhibited the growth of RAS-mutant cancer cells irrespective of the RAS mutation or isozyme. Wild-type RAS (RASWT) cancer cells with GTP-activated RAS from upstream mutations were equally sensitive. Conversely, RASWT cancer cells harboring downstream BRAF mutations and normal cells were essentially insensitive to ADT-007. Sensitivity of cancer cells to ADT-007 required activated RAS and dependence on RAS for proliferation, whereas insensitivity was attributed to metabolic deactivation by UDP-glucuronosyltransferases that were expressed in RASWT and normal cells but repressed in RAS-mutant cancer cells. ADT-007 displayed unique advantages over KRAS mutant-specific, pan-KRAS, and pan-RAS inhibitors that could impact in vivo antitumor efficacy by escaping compensatory mechanisms that lead to resistance. Local administration of ADT-007 showed robust antitumor activity in syngeneic immunocompetent and xenogeneic immune-deficient mouse models of colorectal and pancreatic cancers. The antitumor activity of ADT-007 was associated with the suppression of MAPK signaling and activation of innate and adaptive immunity in the tumor immune microenvironment. Oral administration of ADT-007 prodrug also inhibited tumor growth. Thus, ADT-007 has the potential to address the complex RAS mutational landscape of many human cancers and to improve treatment of RAS-driven tumors. Significance: ADT-007, a first-in-class pan-RAS inhibitor, has unique selectivity for cancer cells with mutant RAS or activated RAS protein and the capability to circumvent resistance to suppress tumor growth, supporting further development of ADT-007 analogs.

Efficacy of first-line chemotherapy combined with immunotherapy or anti-angiogenic therapy in advanced KRAS-mutant non-small cell lung cancer

BACKGROUND

Approximately 30 % non-small cell lung cancer (NSCLC) patients carry KRAS mutations in western countries. First-line chemotherapy combined with immunotherapy has been the standard therapeutic regimen for KRAS-mutant NSCLC patients. This population could also benefit from chemotherapy combined with anti-angiogenic therapy. However, few studies has reported on head-to-head efficacy comparisons between these two treatment strategies.

METHODS

We selected stage IV KRAS-mutated NSCLC patients diagnosed from 2017 to 2022. Their clinical baseline characteristics, first-line treatment strategy, whether combined TP53 or STK11 mutation, PD-L1 expression level, etc. were evaluated. The correlation between these factors and progression-free survival (PFS) and overall survival (OS) were analyzed.

RESULTS

A total of 273 patients received first-line systematic therapy. The most common mutation was KRAS G12C (34.3 %). First-line chemotherapy combined with immunotherapy brought significant survival benefits (mPFS: 11.0 months vs. 4.0 months, P = 0.0003; mOS: 17.0 months vs. 9.0 months, P = 0.0002) compared with first-line chemotherapy combined with anti-angiogenic therapy. Among the 203 patients who received first-line chemotherapy combined with immunotherapy, PD-L1 positive NSCLC patients responded better than PD-L1 negative patients (mPFS: 11.0 months vs. 4.0 months, P = 0.0004; mOS: 21.0 months vs. 11.0 months, P = 0.0005). ECOG PS score of 0-1 (HR=0.201, P = 0.001) and first-line chemotherapy combined with immunotherapy (HR=0.333, P = 0.009) were independent predictors of OS.

CONCLUSIONS

Compared with first-line chemotherapy combined with anti-angiogenic therapy, first-line chemotherapy combined with immunotherapy has brought significant survival benefit to advanced KRAS mutant NSCLC patients, especially for PD-L1 positive patients.

KRAS Mutations in Cancer: Understanding Signaling Pathways to Immune Regulation and the Potential of Immunotherapy

The Kirsten rat sarcoma viral oncogene homologue (KRAS) mutation is one of the most prevailing mutations in various tumors and is difficult to cure. Long-term proliferation in carcinogenesis is primarily initiated by oncogenic KRAS-downstream signaling. Recent research suggests that it also activates the autocrine effect and interplays the tumor microenvironment (TME). Here, we discuss the emerging research, including KRAS mutations to immune evasion in TME, which induce immunological modulation that promotes tumor development. This review gives an overview of the existing knowledge of the underlying connection between KRAS mutations and tumor immune modulation. It also addresses the mechanisms to reduce the effect of oncogenes on the immune system and recent advances in clinical trials for immunotherapy in KRAS-mutated cancers.

Genome-wide CRISPR screening identifies PHF8 as an effective therapeutic target for KRAS- or BRAF-mutant colorectal cancers

BACKGROUND

Mutations in KRAS and BRAF genes are prevalent in colorectal cancer (CRC), which strikingly promote tumorigenesis and lead to poor response to a variety of treatments including immunotherapy by activating the MAPK/ERK pathway. Thus, there is an urgent need to discover effective therapeutic targets and strategies.

METHODS

CRISPR-Cas9 lentiviral knockout library was used to screen the suppressors of anti-PD1 immunotherapy. Bioinformatic analysis was used to analyze the correlation between PHF8 expression and immune indicators in CRC. In vitro and in vivo experiments were utilized to determine the effects of PHF8 on the immune indexes and malignant phenotypes of CRC cells. qRT-PCR, western blotting, immunohistochemical (IHC) staining, and chromatin immunoprecipitation (ChIP)-qPCR assays were used to determine the regulatory effects of PHF8 on PD-L1, KRAS, BRAF, and c-Myc and the regulatory effect c-Myc/miR-22-3p signaling axis on PHF8 expression in CRC cells.

RESULTS

This study identified histone lysine demethylase PHF8 as a negative regulator for the efficacy of anti-PD1 therapy and found that it was highly expressed in CRCs and strongly associated with poor patient survival. Functional studies showed that PHF8 played an oncogenic role in KRAS- or BRAF-mutant CRC cells, but not in wild-type ones. Mechanistically, PHF8 up-regulated the expression of PD-L1, KRAS, BRAF, and c-Myc by increasing the levels of transcriptional activation marks H3K4me3 and H3K27ac and decreasing the levels of transcriptional repression mark H3K9me2 within their promoter regions, promoting immune escape and tumor progression. Besides, our data also demonstrated that PHF8 was up-regulated by the c-Myc/miR-22-3p signaling axis to form a positive feedback loop. Targeting PHF8 substantially improved the efficacy of anti-PD1 therapy and inhibited the malignant phenotypes of KRAS- or BRAF-mutant CRC cells.

CONCLUSION

Our data demonstrate that PHF8 may be an effective therapeutic target for KRAS- or BRAF-mutant CRCs.

Copper-enriched automotive brake wear particles perturb human alveolar cellular homeostasis

BACKGROUND

Airborne fine particulate matter with diameter < 2.5 μm (PM2.5), can reach the alveolar regions of the lungs, and is associated with over 4 million premature deaths per year worldwide. However, the source-specific consequences of PM2.5 exposure remain poorly understood. A major, but unregulated source is car brake wear, which exhaust emission reduction measures have not diminished.

METHODS

We used an interdisciplinary approach to investigate the consequences of brake-wear PM2.5 exposure upon lung alveolar cellular homeostasis using diesel exhaust PM as a comparator. This involved RNA-Seq to analyse global transcriptomic changes, metabolic analyses to investigate glycolytic reprogramming, mass spectrometry to determine PM composition, and reporter assays to provide mechanistic insight into differential effects.

RESULTS

We identified brake-wear PM from copper-enriched non-asbestos organic, and ceramic brake pads as inducing the greatest oxidative stress, inflammation, and pseudohypoxic HIF activation (a pathway implicated in diseases associated with air pollution exposure, including cancer, and pulmonary fibrosis), as well as perturbation of metabolism, and metal homeostasis compared with brake wear PM from low- or semi-metallic pads, and also, importantly, diesel exhaust PM. Compositional and metal chelator analyses identified that differential effects were driven by copper.

CONCLUSIONS

We demonstrate here that brake-wear PM may perturb cellular homeostasis more than diesel exhaust PM. Our findings demonstrate the potential differences in effects, not only for non-exhaust vs exhaust PM, but also amongst different sources of non-exhaust PM. This has implications for our understanding of the potential health effects of road vehicle-associated PM. More broadly, our findings illustrate the importance of PM composition on potential health effects, highlighting the need for targeted legislation to protect public health.

Immunomodulatory role of oncogenic alterations in non-small cell lung cancer: a review of implications for immunotherapy

Immune checkpoint inhibitors (ICIs) have improved clinical outcomes in patients with non-small cell lung cancer (NSCLC) lacking targetable oncogenic alterations. However, their efficacy in individuals with such genomic alterations remains heterogeneous and poorly understood. In detail, certain oncogenic alterations in TP53, EGFR (uncommon mutations), KRAS (G12C), BRAF (non-V600E), MET (amplifications), FGFR1 and FGFR4, actively modify MAPK, PI3K, and STING signaling, thus remodeling tumoral immune phenotype and are associated with high TMB counts, enriched T lymphocyte tumor infiltration, and high expression of antigen-presenting molecules, supporting their consideration as part of the eligibility criteria for ICIs treatment. Nonetheless, other oncogenic alterations are associated with an immunosuppressive TME, low TMB counts, and downregulation of targetable immune checkpoints, in which novel therapeutic approaches are currently being tested to overcome their intrinsic resistance. In this context, this review discusses the fundamental mechanisms by which frequent driver alterations affect ICIs efficacy in patients with NSCLC, and outlines their prognostic relevance in the era of immunotherapy.

Natural products targeting RAS by multiple mechanisms and its therapeutic potential in cancer: An update since 2020

RAS proteins, as pivotal signal transduction molecules, are frequently mutated and hyperactivated in various human cancers, closely associated with tumor cell proliferation, survival, and metastasis. Despite extensive research on RAS targeted therapies, developing effective RAS inhibitors remains a significant challenge. Natural products, endowed with unique chemical structures and diverse biological activities through long-term natural selection, have emerged as a vital resource for discovering novel RAS-targeted therapeutic drugs. This review focuses on the latest advancements in targeting RAS with natural products and categorizes these natural products based on their mechanisms of action. Additionally, we discuss the challenges faced by these natural products during clinical translation, including issues related to pharmacokinetics. Strategies such as combination therapy, structural optimization, and drug delivery systems are anticipated to enhance efficacy and overcome these challenges.

Current Strategies and Future Dimensions in the Development of KRAS Inhibitors for Targeted Anticancer Therapy

KRAS is a proto-oncogene that is found to be mutated in 15% of all metastatic cancers with high prevalence in pancreatic, lung, and colorectal cancers. Additionally, patients harboring KRAS mutations respond poorly to standard cancer therapy. As a result, KRAS is seen as an attractive target for targeted anticancer therapy. Over the last decade, this protein has evolved from being termed "undruggable" to producing two clinically approved drugs along with several more in clinical development, and many under preclinical investigations. This review details the development of various KRAS-targeted molecules with emphasis on the different drug design strategies employed by examining the following areas: (1) Direct inhibition of KRAS mutants using small molecule binders, (2) Inhibiting the activated state of KRAS mutants using a binary complex of small molecule binders and cyclophilin A, and (3) Targeted degradation of KRAS mutants using the PROTAC approach. We assess the pharmacological attributes and possible clinical benefits of the different molecules and look to the next frontiers in the application of KRAS inhibitors as anticancer agents.

KRAS inhibitors: resistance drivers and combinatorial strategies

In 1982, the RAS genes HRAS and KRAS were discovered as the first human cancer genes, with KRAS later identified as one of the most frequently mutated oncogenes. Yet, it took nearly 40 years to develop clinically effective inhibitors for RAS-mutant cancers. The discovery in 2013 by Shokat and colleagues of a druggable pocket in KRAS paved the way to FDA approval of the first covalently binding KRASG12C inhibitors, sotorasib and adagrasib, in 2021 and 2022, respectively. However, rather than marking the end of a successful assault on the Mount Everest of cancer research, this landmark only revealed new challenges in RAS drug discovery. In this review, we highlight the progress on defining resistance mechanisms and developing combination treatment strategies to improve patient responses to KRAS therapies.

Immune regulatory genes impact the hot/cold tumor microenvironment, affecting cancer treatment and patient outcomes

Background and aims

Immunologically hot tumors, characterized by an inflamed tumor microenvironment (TME), contrast significantly with immunologically cold tumors. The identification of these tumor immune subtypes holds clinical significance, as hot tumors may exhibit improved prognoses and heightened responsiveness to checkpoint blockade therapy. Nevertheless, as yet there is no consensus regarding the clinically relevant definition of hot/cold tumors, and the influence of immune genes on the formation of hot/cold tumors remains poorly understood.

Methods

Data for 33 different types of cancer were obtained from The Cancer Genome Atlas database, and their immune composition was assessed using the CIBERSORT algorithm. Tumors were categorized as either hot or cold based on their distinct immune composition, ongoing immune response, and overall survival. A customized immunogram was created to identify important immunological characteristics. Kyoto Encyclopedia of Genes and Genomes and Hallmark pathway enrichment were evaluated through gene set variation analysis. Additionally, hub genes that regulate the tumor microenvironment were identified, and their expression patterns were analyzed using single-cell RNA sequencing. Furthermore, drug sensitivity and molecular docking analyses were performed to identify potential drug candidates capable of transforming cold tumors into hot tumors. For validation, a clinical cohort of patients diagnosed with pancreatic adenocarcinoma was examined using multiplex immunohistochemistry.

Results

We were able to differentiate between hot and cold tumors in various types of cancer (bladder urothelial carcinoma, pancreatic adenocarcinoma, and cervical squamous cell carcinoma) by analyzing the presence of CD8+ T cells, activated natural killer cells, and M2-type macrophages, as well as the cytolytic activity and T cell proliferation. Hub genes that regulate the TME, including PDCD1, CD276, and NT5E, were discovered. The increased expression of NT5E and its prognostic significance were confirmed through multiplex immunohistochemistry in pancreatic adenocarcinoma. Finally, dasatinib and tozasertib were identified as drug candidates capable of converting cold pancreatic adenocarcinoma tumors into hot tumors.

Conclusion

In this study, we developed a framework for discerning clinically significant immune subtypes across various cancer types, further identifying several potential targets for converting cold tumors into hot tumors to enhance anticancer treatment efficacy.

Cyclic nucleotide phosphodiesterases as drug targets

Cyclic nucleotides are synthesized by adenylyl and/or guanylyl cyclase, and downstream of this synthesis, the cyclic nucleotide phosphodiesterase families (PDEs) specifically hydrolyze cyclic nucleotides. PDEs control cyclic adenosine-3',5'monophosphate (cAMP) and cyclic guanosine-3',5'-monophosphate (cGMP) intracellular levels by mediating their quick return to the basal steady state levels. This often takes place in subcellular nanodomains. Thus, PDEs govern short-term protein phosphorylation, long-term protein expression, and even epigenetic mechanisms by modulating cyclic nucleotide levels. Consequently, their involvement in both health and disease is extensively investigated. PDE inhibition has emerged as a promising clinical intervention method, with ongoing developments aiming to enhance its efficacy and applicability. In this comprehensive review, we extensively look into the intricate landscape of PDEs biochemistry, exploring their diverse roles in various tissues. Furthermore, we outline the underlying mechanisms of PDEs in different pathophysiological conditions. Additionally, we review the application of PDE inhibition in related diseases, shedding light on current advancements and future prospects for clinical intervention. SIGNIFICANCE STATEMENT: Regulating PDEs is a critical checkpoint for numerous (patho)physiological conditions. However, despite the development of several PDE inhibitors aimed at controlling overactivated PDEs, their applicability in clinical settings poses challenges. In this context, our focus is on pharmacodynamics and the structure activity of PDEs, aiming to illustrate how selectivity and efficacy can be optimized. Additionally, this review points to current preclinical and clinical evidence that depicts various optimization efforts and indications.

Dynamic Multilevel Regulation of EGFR, KRAS, and MYC Oncogenes: Driving Cancer Cell Proliferation Through (Epi)Genetic and Post-Transcriptional/Translational Pathways

The epidermal growth factor receptor (EGFR) regulates gene expression through two primary mechanisms: as a growth factor in the nucleus, where it translocates upon binding its ligand, or via its intrinsic tyrosine kinase activity in the cytosol, where it modulates key signaling pathways such as RAS/MYC, PI3K, PLCγ, and STAT3. During tumorigenesis, these pathways become deregulated, leading to uncontrolled proliferation, enhanced migratory and metastatic capabilities, evasion of programmed cell death, and resistance to chemotherapy or radiotherapy. The RAS and MYC oncogenes are pivotal in tumorigenesis, driving processes such as resistance to apoptosis, replicative immortality, cellular invasion and metastasis, and metabolic reprogramming. These oncogenes are subject to regulation by a range of epigenetic and post-transcriptional modifications. This review focuses on the deregulation of EGFR, RAS, and MYC expression caused by (epi)genetic alterations and post-translational modifications. It also explores the therapeutic potential of targeting these regulatory proteins, emphasizing the importance of phenotyping neoplastic tissues to inform the treatment of cancer.

Immunotherapy in Oncogene-Addicted NSCLC: Evidence and Therapeutic Approaches

Non-small cell lung cancer (NSCLC) remains a leading cause of cancer-related mortality worldwide. The discovery of specific driver mutations has revolutionized the treatment landscape of oncogene-addicted NSCLC through targeted therapies, significantly improving patient outcomes. However, immune checkpoint inhibitors (ICIs) have demonstrated limited effectiveness in this context. Emerging evidence, though, reveals significant heterogeneity among different driver mutation subgroups, suggesting that certain patient subsets may benefit from ICIs, particularly when combined with other therapeutic modalities. In this review, we comprehensively examine the current evidence on the efficacy of immunotherapy in oncogene-addicted NSCLC. By analyzing recent clinical trials and preclinical studies, along with an overview of mechanisms that may reduce immunotherapy efficacy, we explored potential strategies to address these challenges, to provide insights that could optimize immunotherapy approaches and integrate them effectively into the treatment algorithm for oncogene-addicted NSCLC.

Progress of Immune Checkpoint Inhibitors Therapy for pMMR/MSS Metastatic Colorectal Cancer

Immunotherapy is one of the research hotspots in colorectal cancer field in recent years. The colorectal cancer patients with mismatch repair-deficient (dMMR) or high microsatellite instability (MSI-H) are the primary beneficiaries of immunotherapy. However, the vast majority of colorectal cancers are mismatch repair proficient (pMMR) or microsatellite stability (MSS), and their immune microenvironment is characterized by "cold tumors" that are generally insensitive to single immunotherapy based on immune checkpoint inhibitors (ICIs). Studies have shown that some pMMR/MSS colorectal cancer patients regulate the immune microenvironment by combining other treatments, such as multi-target tyrosine kinase inhibitors, anti-vascular endothelial growth factor (VEGF) monoclonal antibodies, chemotherapy, radiotherapy, anti-epithelial growth factor receptor (EGFR) monoclonal antibodies, and mitogen-activated protein kinase (MAPK) signaling pathway inhibitors and oncolytic viruses, etc. to transform "cold tumor" into "hot tumor", thereby improving the response to immunotherapy. In addition, screening for potential prognostic biomarkers can also enrich the population benefiting from immunotherapy for microsatellite stable colorectal cancer. Therefore, in pMMR or MSS metastatic colorectal cancer (mCRC), the optimization of immunotherapy regimens and the search for effective efficacy prediction biomarkers are currently important research directions. In this paper, we review the progress of efficacy of immunotherapy (mainly ICIs) in pMMR /MSS mCRC, challenges and potential markers, in order to provide research ideas for the development of immunotherapy for mCRC.

Role of PD-1/PD-L1 signaling axis in oncogenesis and its targeting by bioactive natural compounds for cancer immunotherapy

Cancer is a global health problem and one of the leading causes of mortality. Immune checkpoint inhibitors have revolutionized the field of oncology, emerging as a powerful treatment strategy. A key pathway that has garnered considerable attention is programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1). The interaction between PD-L1 expressed on tumor cells and PD-1 reduces the innate immune response and thus compromises the capability of the body's immune system. Furthermore, it controls the phenotype and functionality of innate and adaptive immune components. A range of monoclonal antibodies, including avelumab, atezolizumab, camrelizumab, dostarlimab, durvalumab, sinitilimab, toripalimab, and zimberelimab, have been developed for targeting the interaction between PD-1 and PD-L1. These agents can induce a broad spectrum of autoimmune-like complications that may affect any organ system. Recent studies have focused on the effect of various natural compounds that inhibit immune checkpoints. This could contribute to the existing arsenal of anticancer drugs. Several bioactive natural agents have been shown to affect the PD-1/PD-L1 signaling axis, promoting tumor cell apoptosis, influencing cell proliferation, and eventually leading to tumor cell death and inhibiting cancer progression. However, there is a substantial knowledge gap regarding the role of different natural compounds targeting PD-1 in the context of cancer. Hence, this review aims to provide a common connection between PD-1/PD-L1 blockade and the anticancer effects of distinct natural molecules. Moreover, the primary focus will be on the underlying mechanism of action as well as the clinical efficacy of bioactive molecules. Current challenges along with the scope of future research directions targeting PD-1/PD-L1 interactions through natural substances are also discussed.

MAZ promotes tumor proliferation and immune evasion in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most dominant histological subtype of lung cancer and one of the most lethal malignancies. The identification of novel therapeutic targets is required for the treatment of LUAD. Here, we showed that MYC-associated zinc-finger protein (MAZ) is upregulated in LUAD tissues. MAZ expression levels are inversely correlated with patient survival. Silencing of MAZ decreased tumor proliferation and the expression of pro-tumorigenic chemokines and Galectin-9 (Gal-9), an immune checkpoint molecule. The pro-tumorigenic chemokines and Gal-9 induce immune suppression by recruitment of myeloid cells and inhibition of T cell activation, respectively. Mechanistically, MAZ transcriptionally regulates KRAS expression and activates its downstream AKT-NF-κB signaling pathway, which is crucial for tumor progression and immune evasion. Additionally, in vivo animal models and bioinformatic analyses indicated that MAZ suppression could enhance the efficacy of immune checkpoint blockade (ICB) therapy for LUAD. Overall, our results suggest that MAZ plays an important role in regulating cell proliferation and immune evasion via KRAS/AKT/NF-κB signaling in LUAD. Our findings offer a candidate molecular target for LUAD therapy, with implications for improving the efficacy of ICB therapy.

KRAS mutations in endometrial cancers: Possible prognostic and treatment implications

BACKGROUND/OBJECTIVES

Patients with recurrent or metastatic endometrial cancer (EC) have poor prognoses with limited therapeutic options following immunotherapy or immunochemotherapy treatments. Inhibitors of KRAS mutations (KRAS-mut) have shown efficacy in early solid tumor studies, but data in EC are lacking. This study describes the frequency of KRAS-mut relative to other oncogenic alterations in EC to identify genomic characteristics of KRAS-mut tumors that could lead to novel therapeutic options.

METHODS

A molecular database of 7870 ECs was queried for presence of oncogenic mutations and immunotherapy biomarkers. Comparisons were performed using Fisher-Exact/ChiSquare (p-values) and adjusted for multiple tests by Benjamini-Hochberg (q) and pairwise nonparametric analysis using Wilcoxon Method.

RESULTS

KRAS-mut is a relatively frequent genotype in EC, detected in 16% of cases. Codon 12 was most frequently mutated, with G12D (31%) and G12V (27%) the most common subtypes. Biomarkers of immunotherapy response co-occur with KRAS-mut. Microsatellite instability-high and tumor mutational burden-high status were observed in 34.1% and 36.5% in KRAS-mut compared to 19.8% and 16.9% in KRAS-WT, respectively (p < 0.05). PD-L1 >1% was detected in 8.4% vs 6.4% of KRAS-mut vs KRAS-WT (p < 0.05). BRCA1/2 mutations were detected with similar low frequency (5.9% vs 4.9%) among KRAS-mut and KRAS-WT ECs (p > 0.05). KRAS-mut was inversely associated with Her-2 overexpression (1.8% KRAS-mut vs 13% KRAS-WT. (p < 0.001).

CONCLUSIONS

KRAS-mut represents a genotypically distinct group of ECs. Overlap exists with genomic predictors (TMB-high, MSI-high) of immunotherapy response, suggesting a possible biomarker-driven combination option with immunotherapy. Clinical trials to evaluate these strategies should be developed.

Cellular mechanisms of combining innate immunity activation with PD-1/PD-L1 blockade in treatment of colorectal cancer

PD-1/PD-L1 blockade therapies have displayed extraordinary clinical efficacy for melanoma, renal, bladder and lung cancer; however, only a minority of colorectal cancer (CRC) patients benefit from these treatments. The efficacy of PD-1/PD-L1 blockade in CRC is limited by the complexities of tumor microenvironment. PD-1/PD-L1 blockade immunotherapy is based on T cell-centered view of tumor immunity. However, the onset and maintenance of T cell responses and the development of long-lasting memory T cells depend on innate immune responses. Acknowledging the pivotal role of innate immunity in anti-tumor immune response, this review encapsulates the employment of combinational therapies those involve PD-1/PD-L1 blockade alongside the activation of innate immunity and explores the underlying cellular mechanisms, aiming to harnessing innate immune responses to induce long-lasting tumor control for CRC patients who received PD-1/PD-L1 blockade therapy.

Depicting the cellular complexity of pancreatic adenocarcinoma by Imaging Mass Cytometry: focus on cancer-associated fibroblasts

Introduction

Pancreatic ductal adenocarcinoma (PDAC) represents the complexity of interaction between cancer and cells of the tumor microenvironment (TME). Immune cells affect tumor cell behavior, thus driving cancer progression. Cancer-associated fibroblasts (CAFs) are responsible of the desmoplastic and fibrotic reaction by regulating deposition and remodeling of extracellular matrix (ECM). As tumor-promoting cells abundant in PDAC ECM, CAFs represent promising targets for novel anticancer interventions. However, relevant clinical trials are hampered by the lack of specific markers and elusive differences among CAF subtypes. Indeed, while single-cell transcriptomic analyses have provided important information on the cellular constituents of PDACs and related molecular pathways, studies based on the identification of protein markers in tissues aimed at identifying CAF subtypes and new molecular targets result incomplete.

Methods

Herein, we applied multiplexed Imaging Mass Cytometry (IMC) at single-cell resolution on 8 human PDAC tissues to depict the PDAC composing cells, and profiling immune cells, endothelial cells (ECs), as well as endocrine cells and tumor cells.

Results

We focused on CAFs by characterizing up to 19 clusters distinguished by phenotype, spatiality, and interaction with immune and tumor cells. We report evidence that specific subtypes of CAFs (CAFs 10 and 11) predominantly are enriched at the tumor-stroma interface and closely associated with tumor cells. CAFs expressing different combinations of FAP, podoplanin and cadherin-11, were associated with a higher level of CA19-9. Moreover, we identified specific subsets of FAP+ and podoplanin+/cadherin-11+ CAFs enriched in patients with negative prognosis.

Discussion

The present study provides new general insights into the complexity of the PDAC microenvironment by defining phenotypic heterogeneities and spatial distributions of CAFs, thus suggesting different functions of their subtypes in the PDAC microenvironment.

Base editing screens define the genetic landscape of cancer drug resistance mechanisms

Drug resistance is a principal limitation to the long-term efficacy of cancer therapies. Cancer genome sequencing can retrospectively delineate the genetic basis of drug resistance, but this requires large numbers of post-treatment samples to nominate causal variants. Here we prospectively identify genetic mechanisms of resistance to ten oncology drugs from CRISPR base editing mutagenesis screens in four cancer cell lines using a guide RNA library predicted to install 32,476 variants in 11 cancer genes. We identify four functional classes of protein variants modulating drug sensitivity and use single-cell transcriptomics to reveal how these variants operate through distinct mechanisms, including eliciting a drug-addicted cell state. We identify variants that can be targeted with alternative inhibitors to overcome resistance and functionally validate an epidermal growth factor receptor (EGFR) variant that sensitizes lung cancer cells to EGFR inhibitors. Our variant-to-function map has implications for patient stratification, therapy combinations and drug scheduling in cancer treatment.

Cholesterol synthesis is essential for the growth of liver metastasis-prone colorectal cancer cells

Metastasis to the liver is a leading cause of death in patients with colorectal cancer. To investigate the characteristics of cancer cells prone to metastasis, we utilized an isogenic model of BALB/c and colon tumor 26 (C26) cells carrying an active KRAS mutation. Liver metastatic (LM) 1 cells were isolated from mice following intrasplenic transplantation of C26 cells. Subsequent injections of LM1 cells generated LM2 cells, and after four cycles, LM4 cells were obtained. In vitro, using a perfusable capillary network system, we found comparable extravasation frequencies between C26 and LM4 cells. Both cell lines showed similar growth rates in vitro. However, C26 cells showed higher glucose consumption, whereas LM4 cells incorporated more fluorescent fatty acids (FAs). Biochemical analysis revealed that LM4 cells had higher cholesterol levels than C26 cells. A correlation was observed between fluorescent FAs and cholesterol levels detected using filipin III. LM4 cells utilized FAs as a source for cholesterol synthesis through acetyl-CoA metabolism. In cellular analysis, cholesterol accumulated in punctate regions, and upregulation of NLRP3 and STING proteins, but not mTOR, was observed in LM4 cells. Treatment with a cholesterol synthesis inhibitor (statin) induced LM4 cell death in vitro and suppressed LM4 cell growth in the livers of nude mice. These findings indicate that colorectal cancer cells prone to liver metastasis show cholesterol-dependent growth and that statin therapy could help treat liver metastasis in immunocompromised patients.

MEK inhibition prevents CAR-T cell exhaustion and differentiation via downregulation of c-Fos and JunB

Clinical evidence supports the notion that T cell exhaustion and terminal differentiation pose challenges to the persistence and effectiveness of chimeric antigen receptor-T (CAR-T) cells. MEK1/2 inhibitors (MEKIs), widely used in cancer treatment due to their ability to inhibit aberrant MAPK signaling, have shown potential synergistic effects when combined with immunotherapy. However, the impact and mechanisms of MEKIs on CAR-T cells remain uncertain and controversial. To address this, we conducted a comprehensive investigation to determine whether MEKIs enhance or impair the efficacy of CAR-T cells. Our findings revealed that MEKIs attenuated CAR-T cell exhaustion and terminal differentiation induced by tonic signaling and antigen stimulation, thereby improving CAR-T cell efficacy against hematological and solid tumors. Remarkably, these effects were independent of the specific scFvs and costimulatory domains utilized in CARs. Mechanistically, analysis of bulk and single-cell transcriptional profiles demonstrates that the effect of MEK inhibition was related to diminish anabolic metabolism and downregulation of c-Fos and JunB. Additionally, the overexpression of c-Fos or JunB in CAR-T cells counteracted the effects of MEK inhibition. Furthermore, our Cut-and-Tag assay revealed that MEK inhibition downregulated the JunB-driven gene profiles associated with exhaustion, differentiation, anergy, glycolysis, and apoptosis. In summary, our research unveil the critical role of the MAPK-c-Fos-JunB axis in driving CAR-T cell exhaustion and terminal differentiation. These mechanistic insights significantly broaden the potential application of MEKIs to enhance the effectiveness of CAR-T therapy.

A Novel Pan-RAS Inhibitor with a Unique Mechanism of Action Blocks Tumor Growth in Mouse Models of GI Cancer

Here, we describe a novel pan-RAS inhibitor, ADT-007, that potently inhibited the growth of RAS mutant cancer cells irrespective of the RAS mutation or isozyme. RAS WT cancer cells with GTP-activated RAS from upstream mutations were equally sensitive. Conversely, RAS WT cancer cells harboring downstream BRAF mutations and normal cells were essentially insensitive to ADT-007. Sensitivity of cancer cells to ADT-007 required activated RAS and dependence on RAS for proliferation, while insensitivity was attributed to metabolic deactivation by UDP-glucuronosyltransferases expressed in RAS WT and normal cells but repressed in RAS mutant cancer cells. ADT-007 binds nucleotide-free RAS to block GTP activation of effector interactions and MAPK/AKT signaling, resulting in mitotic arrest and apoptosis. ADT-007 displayed unique advantages over mutant-specific KRAS and pan-KRAS inhibitors, as well as other pan-RAS inhibitors that could impact in vivo antitumor efficacy by escaping compensatory mechanisms leading to resistance. Local administration of ADT-007 showed robust antitumor activity in syngeneic immune-competent and xenogeneic immune-deficient mouse models of colorectal and pancreatic cancer. The antitumor activity of ADT-007 was associated with the suppression of MAPK signaling and activation of innate and adaptive immunity in the tumor immune microenvironment. Oral administration of ADT-007 prodrug also inhibited tumor growth, supporting further development of this novel class of pan-RAS inhibitors for RAS-driven cancers.

SIGNIFICANCE

ADT-007 has unique pharmacological properties with distinct advantages over other RAS inhibitors by circumventing resistance and activating antitumor immunity. ADT-007 prodrugs and analogs with oral bioavailability warrant further development for RAS-driven cancers.

Oncogenic KRAS drives immunosuppression of colorectal cancer by impairing DDX60-mediated dsRNA accumulation and viral mimicry

The interferon (IFN) response is vital for the effectiveness of immune checkpoint inhibition (ICI) therapy. Our previous research showed that KRAS (Kirsten rat sarcoma viral) mutation impairs the IFN response in colorectal cancer (CRC), with an unclear mechanism. Here, we demonstrate that KRAS accelerates double-stranded RNA (dsRNA) degradation, impairing dsRNA sensing and IFN response by down-regulating DExD/H-box helicase 6 (DDX60). DDX60 was identified as a KRAS target here and could bind to dsRNAs to protect against RNA-induced silencing complex (RISC)-mediated degradation. Overexpressing DDX60 induced dsRNA accumulation, reactivated IFN signaling, and increased CRC sensitivity to ICI therapy. Mechanistically, KRAS engaged the AKT (also known as protein kinase B)-GSK3β (glycogen synthase kinase-3 beta) pathway to suppress STAT3 phosphorylation, thereby inhibiting STAT3-driven DDX60 transcription. Our findings reveal a role for KRAS in dsRNA homeostasis, suggesting potential strategies to convert "cold" tumors to "hot" and to overcome ICI resistance in CRC with KRAS mutations.

Intermittent MEK Inhibition with GITR Costimulation Rescues T-cell Function for Increased Efficacy with CTLA-4 Blockade in Solid Tumor Models

MEK inhibitors (MEKi) have shown limited success as a treatment for MAPK/ERK pathway-dependent cancers due to various resistance mechanisms tumor cells can employ. CH5126766 (CKI27) is an inhibitor that binds to MEK and prevents release of RAF, reducing the relief of negative feedback commonly observed with other MEKis. We observed that CKI27 increased MHC expression in tumor cells and improved T cell-mediated killing. Yet, CKI27 also decreased T-cell proliferation, activation, and cytolytic activity by inhibiting the MAPK/ERK pathway that is activated downstream of T-cell receptor signaling. Therefore, we aimed to balance the positive and negative immunomodulatory effects of MEKis for optimal combination with immunotherapy. Intermittent administration of CKI27 allowed T cells to partially recover and costimulation via GITR and OX-40 agonist antibodies completely alleviated inhibition of function. In Kras mutant lung and colon tumor mouse models, intermittent CKI27 and anti-GITR significantly decreased tumor growth and prolonged survival when further combined with CTLA-4 immune checkpoint blockade. Moreover, this triple combination increased CD8+ and CD4+ T-cell proliferation, activation, and effector/memory subsets in the tumor-draining lymph nodes and tumors and led to intratumoral regulatory T-cell destabilization. These data, collectively, will allow for more informed decisions when optimizing combination regimens by overcoming resistance, reducing toxicity, and generating long-term immune responses.

Parthenolide Inhibits Synthesis and Promotes Degradation of Programmed Cell Death Ligand 1 and Enhances T Cell Tumor-Killing Activity

Parthenolide is a germacrane sesquiterpene lactone separated from the traditional medicinal plant feverfew. Previous studies have shown that parthenolide possesses many pharmacological activities, involving anti-inflammatory and anticancer activities. However, the antitumor mechanism of parthenolide has not been fully elucidated. Thus, we investigate the potential antitumor mechanisms of parthenolactone. We predicted through network pharmacology that parthenolide may target HIF-1α to interfere with the occurrence and development of cancer. We found that parthenolide inhibited PD-L1 protein synthesis through mTOR/p70S6K/4EBP1/eIF4E and RAS/RAF/MEK/MAPK signaling pathways and promoted PD-L1 protein degradation through the lysosomal pathway, thereby inhibiting PD-L1 expression. Immunoprecipitation and Western blotting results demonstrated that parthenolide inhibited PD-L1 expression by suppressing HIF-1α and RAS cooperatively. We further proved that parthenolide inhibited cell proliferation, migration, invasion, and tube formation via down-regulating PD-L1. Moreover, parthenolide increased the effect of T cells to kill tumor cells. In vivo xenograft assays further demonstrated that parthenolide suppressed the growth of tumor xenografts. Collectively, we report for the first time that parthenolide enhanced T cell tumor-killing activity and suppressed cell proliferation, migration, invasion, and tube formation by PD-L1. The current study provides new insight for the development of parthenolide as a novel anticancer drug targeting PD-L1.

Barriers and opportunities in pancreatic cancer immunotherapy

Pancreatic ductal adenocarcinoma (PDAC) presents a fatal clinical challenge characterized by a dismal 5-year overall survival rate, primarily due to the lack of early diagnosis and limited therapeutic efficacy. Immunotherapy, a proven success in multiple cancers, has yet to demonstrate significant benefits in PDAC. Recent studies have revealed the immunosuppressive characteristics of the PDAC tumor microenvironment (TME), including immune cells with suppressive properties, desmoplastic stroma, microbiome influences, and PDAC-specific signaling pathways. In this article, we review recent advances in understanding the immunosuppressive TME of PDAC, TME differences among various mouse models of pancreatic cancer, and the mechanisms underlying resistance to immunotherapeutic interventions. Furthermore, we discuss the potential of targeting cancer cell-intrinsic pathways and TME components to sensitize PDAC to immune therapies, providing insights into strategies and future perspectives to break through the barriers in improving pancreatic cancer treatment.

CDYL loss promotes cervical cancer aggression by increasing PD-L1 expression via the suppression of IRF2BP2 transcription

BACKGROUND

Recurrent or metastatic cervical cancer have an extremely low 5-year survival rates about 17% due to limited therapeutic options. CDYL plays a critical role in multiple cancer development, as an oncogene or tumor suppressor in a context-dependent manner. However, the role of CDYL in cervical carcinogenesis has not yet been explored.

METHODS

CDYL expression was examined in cervical cancer and cell lines. The effect of CDYL/IRF2BP2/PD-L1 axis on malignant phenotypes of cervical cancer cells were tested with gain-of-function experiments. A mouse model of cervical cancer was developed to validate the in vitro results.

RESULTS

Clinical data analysis revealed that CDYL was downregulated and associated with a poor prognosis in cervical cancer patients. CDYL overexpression suppressed cervical cancer cells proliferation and invasion in vitro and vivo assays and enhanced the immune response by decreasing PD-L1 expression and reversing the tumor immunosuppressing microenvironment. Mechanistically, CDYL inhibited the PD-L1 expression through transcriptionally suppressing IRF2BP2 in cervical cancer cells.

CONCLUSIONS

Taken together, our findings established the crucial role of CDYL in cervical carcinogenesis and sensitivity for immune checkpoint blockade therapy, and supported the hypothesis that CDYL could be a potential novel immunotherapy response predictive biomarker for cervical cancer patients.

Immune status and combined immunotherapy progression in Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutant tumors

Kirsten rat sarcoma viral oncogene homolog (KRAS) is the most frequently mutated oncogene, occurring in various tumor types. Despite extensive efforts over the past 40 years to develop inhibitors targeting KRAS mutations, resistance to these inhibitors has eventually emerged. A more precise understanding of KRAS mutations and the mechanism of resistance development is essential for creating novel inhibitors that target specifically KRAS mutations and can delay or overcome resistance. Immunotherapy has developed rapidly in recent years, and in-depth dissection of the tumor immune microenvironment has led researchers to shift their focus to patients with KRAS mutations, finding that immune factors play an essential role in KRAS-mutant (KRAS-Mut) tumor therapy and targeted drug resistance. Breakthroughs and transitions from targeted therapy to immunotherapy have provided new hope for treating refractory patients. Here, we reviewed KRAS mutation-targeted treatment strategies and resistance issues, focusing on our in-depth exploration of the specific immune status of patients with KRAS mutations and the impact of body immunity following KRAS inhibition. We aimed to guide innovative approaches combining RAS inhibition with immunotherapy, review advances in preclinical and clinical stages, and discuss challenges and future directions.

Immune modulatory microRNAs in tumors, their clinical relevance in diagnosis and therapy

The importance of the immune system in regulating tumor growth by inducing immune cell-mediated cytotoxicity associated with patients' outcomes has been highlighted in the past years by an increasing life expectancy in patients with cancer on treatment with different immunotherapeutics. However, tumors often escape immune surveillance, which is accomplished by different mechanisms. Recent studies demonstrated an essential role of small non-coding RNAs, such as microRNAs (miRNAs), in the post-transcriptional control of immune modulatory molecules. Multiple methods have been used to identify miRNAs targeting genes involved in escaping immune recognition including miRNAs targeting CTLA-4, PD-L1, HLA-G, components of the major histocompatibility class I antigen processing machinery (APM) as well as other immune response-relevant genes in tumors. Due to their function, these immune modulatory miRNAs can be used as (1) diagnostic and prognostic biomarkers allowing to discriminate between tumor stages and to predict the patients' outcome as well as response and resistance to (immuno) therapies and as (2) therapeutic targets for the treatment of tumor patients. This review summarizes the role of miRNAs in tumor-mediated immune escape, discuss their potential as diagnostic, prognostic and predictive tools as well as their use as therapeutics including alternative application methods, such as chimeric antigen receptor T cells.

CRISPR/Cas-Mediated Knockdown of PD-L1 and KRAS in Lung Cancer Cells

Cancer cells can escape death and surveillance by the host immune system in various ways. Programmed cell death ligand 1 (PD-L1) is a transmembrane protein that is expressed by most cell types, including cancer cells, and can provide an inhibitory signal to its receptor PD-1, which is expressed on the surface of activated T cells, impairing the immune response. PD-L1/PD-1-mediated immune evasion is observed in several KRAS-mutated cancers. In the current study, we used the CRISPR/Cas9 system to knock down PD-L1 and KRAS in adenocarcinoma lung cells (A549 and H1975). Knockdown of PD-L1 was validated by qPCR and coculture with lymphocytes. The cells were functionally analyzed for cell cycle, migration and apoptosis. In addition, the effects of PD-L1 and KRAS downregulation on chemotherapy sensitivity and expression of inflammatory markers were investigated. Suppression of PD-L1 and KRAS led to a slowdown of the cell cycle in the G0/G1 phase and reduced migration, increased sensitivity to chemotherapy and triggered apoptosis of cancer cells. In addition, the conditioned medium of the modulated cells significantly affected the native cancer cells and reduced their viability and drug resistance. Our study suggests that dual silencing of PD-L1 and KRAS by CRISPR/Cas9 may be a promising therapeutic approach for the treatment of lung cancer.

MYC and KRAS cooperation: from historical challenges to therapeutic opportunities in cancer

RAS and MYC rank amongst the most commonly altered oncogenes in cancer, with RAS being the most frequently mutated and MYC the most amplified. The cooperative interplay between RAS and MYC constitutes a complex and multifaceted phenomenon, profoundly influencing tumor development. Together and individually, these two oncogenes regulate most, if not all, hallmarks of cancer, including cell death escape, replicative immortality, tumor-associated angiogenesis, cell invasion and metastasis, metabolic adaptation, and immune evasion. Due to their frequent alteration and role in tumorigenesis, MYC and RAS emerge as highly appealing targets in cancer therapy. However, due to their complex nature, both oncogenes have been long considered "undruggable" and, until recently, no drugs directly targeting them had reached the clinic. This review aims to shed light on their complex partnership, with special attention to their active collaboration in fostering an immunosuppressive milieu and driving immunotherapeutic resistance in cancer. Within this review, we also present an update on the different inhibitors targeting RAS and MYC currently undergoing clinical trials, along with their clinical outcomes and the different combination strategies being explored to overcome drug resistance. This recent clinical development suggests a paradigm shift in the long-standing belief of RAS and MYC "undruggability", hinting at a new era in their therapeutic targeting.

Stress granules in cancer: Adaptive dynamics and therapeutic implications

Stress granules (SGs), membrane-less cellular organelles formed via liquid-liquid phase separation, are central to how cells adapt to various stress conditions, including endoplasmic reticulum stress, nutrient scarcity, and hypoxia. Recent studies have underscored a significant link between SGs and the process of tumorigenesis, highlighting that proteins, associated components, and signaling pathways that facilitate SG formation are often upregulated in cancer. SGs play a key role in enhancing tumor cell proliferation, invasion, and migration, while also inhibiting apoptosis, facilitating immune evasion, and driving metabolic reprogramming through multiple mechanisms. Furthermore, SGs have been identified as crucial elements in the development of resistance against chemotherapy, immunotherapy, and radiotherapy across a variety of cancer types. This review delves into the complex role of SGs in cancer development and resistance, bringing together the latest progress in the field and exploring new avenues for therapeutic intervention.

The Tumor Microbiome as a Predictor of Outcomes in Patients with Metastatic Melanoma Treated with Immune Checkpoint Inhibitors

Emerging evidence supports the important role of the tumor microbiome in oncogenesis, cancer immune phenotype, cancer progression, and treatment outcomes in many malignancies. In this study, we investigated the metastatic melanoma tumor microbiome and its potential roles in association with clinical outcomes, such as survival, in patients with metastatic disease treated with immune checkpoint inhibitors (ICI). Baseline tumor samples were collected from 71 patients with metastatic melanoma before treatment with ICIs. Bulk RNA sequencing (RNA-seq) was conducted on the formalin-fixed, paraffin-embedded and fresh frozen tumor samples. Durable clinical benefit (primary clinical endpoint) following ICIs was defined as overall survival >24 months and no change to the primary drug regimen (responders). We processed RNA-seq reads to carefully identify exogenous sequences using the {exotic} tool. The age of the 71 patients with metastatic melanoma ranged from 24 to 83 years, 59% were male, and 55% survived >24 months following the initiation of ICI treatment. Exogenous taxa were identified in the tumor RNA-seq, including bacteria, fungi, and viruses. We found differences in gene expression and microbe abundances in immunotherapy-responsive versus nonresponsive tumors. Responders showed significant enrichment of bacteriophages in the phylum Uroviricota, and nonresponders showed enrichment of several bacteria, including Campylobacter jejuni. These microbes correlated with immune-related gene expression signatures. Finally, we found that models for predicting prolonged survival with immunotherapy using both microbe abundances and gene expression outperformed models using either dataset alone. Our findings warrant further investigation and potentially support therapeutic strategies to modify the tumor microbiome in order to improve treatment outcomes with ICIs.

SIGNIFICANCE

We analyzed the tumor microbiome and interactions with genes and pathways in metastatic melanoma treated with immunotherapy and identified several microbes associated with immunotherapy response and immune-related gene expression signatures. Machine learning models that combined microbe abundances and gene expression outperformed models using either dataset alone in predicting immunotherapy responses.