Enzyme-mediated depletion of methylthioadenosine restores T cell function in MTAP-deficient tumors and reverses immunotherapy resistance

PRMT5 inhibitors: Therapeutic potential in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is predominantly driven by mutations in the Kirsten rat sarcoma virus (KRAS) oncogene. Due to the pivotal role of KRAS in PDAC pathogenesis, KRAS inhibitors (KRASi) have recently demonstrated initial signs of clinical efficacy. However, considering currently documented response rates and the resistance development to KRASi, additional targeted therapies are needed. In this context, we provide a summary of recent preclinical and clinical findings on protein arginine methyltransferase 5 (PRMT5) inhibitors (PRMT5i) and their implications for PDAC. PRMT5 has been linked to key oncogenic processes, including epithelial-mesenchymal transition (EMT), MYC and Hippo signaling pathways, glycolysis, and therapy resistance. With further advancements and optimization of PRMT5i-based therapies, these inhibitors hold significant potential as therapeutic agents for PDAC treatment. Therefore, we synthesize the current understanding of PRMT5i and highlight promising directions for future developments in PDAC.

Resilience and vulnerabilities of tumor cells under purine shortage stress

Purine metabolism is a promising therapeutic target in cancer; however how cancer cells respond to purine shortage,particularly their adaptation and vulnerabilities, remains unclear. Using the recently developed purine shortage-inducing prodrug DRP-104 and genetic approaches, we investigated these responses in prostate, lung and glioma cancer models. We demonstrate that when de novo purine biosynthesis is compromised, cancer cells employ microtubules to assemble purinosomes, multi-protein complexes of de novo purine biosynthesis enzymes that enhance purine biosynthesis efficiency. While this process enables tumor cells to adapt to purine shortage stress, it also renders them more susceptible to the microtubule-stabilizing chemotherapeutic drug Docetaxel. Furthermore, we show that although cancer cells primarily rely on de novo purine biosynthesis, they also exploit Methylthioadenosine Phosphorylase (MTAP)-mediated purine salvage as a crucial alternative source of purine supply, especially under purine shortage stress. In support of this finding, combining DRP-104 with an MTAP inhibitor significantly enhances tumor suppression in prostate cancer (PCa) models in vivo. Finally, despite the resilience of the purine supply machinery, purine shortage-stressed tumor cells exhibit increased DNA damage and activation of the cGAS-STING pathway, which may contribute to impaired immunoevasion and provide a molecular basis of the previously observed DRP-104-induced anti-tumor immunity. Together, these findings reveal purinosome assembly and purine salvage as key mechanisms of cancer cell adaptation and resilience to purine shortage while identifying microtubules, MTAP, and immunoevasion deficits as therapeutic vulnerabilities.

Unlocking the mechanisms underlying the activity of pembrolizumab plus enfortumab vedotin in patients with urothelial carcinoma

INTRODUCTION

Urothelial carcinoma (UC) is frequently associated with a poor prognosis in patients with advanced disease. A strong biological rationale supports the investigation of combining antibody-drug conjugates (ADCs) with immunotherapy to overcome the occurrence of resistance and improve patient outcomes.

AREAS COVERED

In this review, we illustrate the mechanisms of action of pembrolizumab and enfortumab vedotin (EV) and the immune and biological rationales underlying their synergy in mUC patients.

EXPERT OPINION

The results of the combination of EV and pembrolizumab represent a ray of light in the therapeutic scenario of mUC patients. A deeper understanding of the mechanisms underlying the synergistic effects of these agents will be crucial to reduce drug-resistance and further improve the outcome of mUC patients.

Tumor‑associated neutrophils: Critical regulators in cancer progression and therapeutic resistance (Review)

Cancer is the second leading cause of death among humans worldwide. Despite remarkable improvements in cancer therapies, drug resistance remains a significant challenge. The tumor microenvironment (TME) is intimately associated with therapeutic resistance. Tumor‑associated neutrophils (TANs) are a crucial component of the TME, which, along with other immune cells, play a role in tumorigenesis, development and metastasis. In the current review, the roles of TANs in the TME, as well as the mechanisms of neutrophil‑mediated resistance to cancer therapy, including immunotherapy, chemotherapy, radiotherapy and targeted therapy, were summarized. Furthermore, strategies for neutrophil therapy were discussed and TANs were explored as potential targets for cancer treatment. In conclusion, the need to explore the precise roles, recruitment pathways and mechanisms of action of TANs was highlighted for the purpose of developing therapies that precisely target TANs and reverse drug resistance.

Methionine intervention induces PD-L1 expression to enhance the immune checkpoint therapy response in MTAP-deleted osteosarcoma

Osteosarcoma (OS), a malignant bone tumor with limited treatment options, exhibits low sensitivity to immune checkpoint therapy (ICT). Through genomics and transcriptomics analyses, we identify a subgroup of OS with methylthioadenosine phosphorylase (MTAP) deletion, which contributes to ICT resistance, leading to a "cold" tumor microenvironment. MTAP-deleted OS relies on methionine metabolism and is sensitive to methionine intervention, achieved through either dietary restriction or inhibition of methionine adenosyltransferase 2a (MAT2A), a key enzyme in methionine metabolism. We further demonstrate that methionine intervention triggers programmed death-ligand 1 (PD-L1) transcription factor IKAROS family zinc finger 1 (IKZF1) and enhances PD-L1 expression in MTAP-deleted OS cells. Methionine intervention also activates the immune-related signaling pathways in MTAP-deleted OS cells and attracts CD8+ T cells, thereby enhancing the efficacy of ICT. Combining methionine intervention with ICT provides a significant survival benefit in MTAP-deleted OS murine models, suggesting a rationale for combination regimens in OS ICT.

Deep Learning Model for Predicting Immunotherapy Response in Advanced Non-Small Cell Lung Cancer

Importance

Only a small fraction of patients with advanced non-small cell lung cancer (NSCLC) respond to immune checkpoint inhibitor (ICI) treatment. For optimal personalized NSCLC care, it is imperative to identify patients who are most likely to benefit from immunotherapy.

Objective

To develop a supervised deep learning-based ICI response prediction method; evaluate its performance alongside other known predictive biomarkers; and assess its association with clinical outcomes in patients with advanced NSCLC.

Design, Setting, and Participants

This multicenter cohort study developed and independently validated a deep learning-based response stratification model for predicting ICI treatment outcome in patients with advanced NSCLC from whole slide hematoxylin and eosin-stained images. Images for model development and validation were obtained from 1 participating center in the US and 3 in the European Union (EU) from August 2014 to December 2022. Data analyses were performed from September 2022 to May 2024.

Exposure

Monotherapy with ICIs.

Main Outcomes and Measures

Model performance measured by clinical end points and objective response rate (ORR) differentiation power vs other predictive biomarkers, ie, programmed death-ligand 1 (PD-L1), tumor mutational burden (TMB), and tumor-infiltrating lymphocytes (TILs).

Results

A total of 295 581 image tiles from 958 patients (mean [SD] age, 66.0 [10.6] years; 456 [48%] females and 502 [52%] males) treated with ICI for NSCLC were included in the analysis. The US-based development cohort consisted of 614 patients with median (IQR) follow-up time of 54.5 (38.2-68.1) months, and the EU-based validation cohort, 344 patients with 43.3 (27.4-53.9) months of follow-up. The ORR to ICI was 26% in the developmental cohort and 28% in the validation cohort. The deep learning model's area under the receiver operating characteristic curve (AUC) for ORR was 0.75 (95% CI, 0.64-0.85) in the internal test set and 0.66 (95% CI, 0.60-0.72) in the validation cohort. In a multivariable analysis, the deep learning model's score was an independent predictor of ICI response in the validation cohort for both progression-free (hazard ratio, 0.56; 95% CI, 0.42-0.76; P < .001) and overall survival (hazard ratio, 0.53; 95% CI, 0.39-0.73; P < .001). The tuned deep learning model achieved a higher AUC than TMB, TILs, and PD-L1 in the internal set; in the validation cohort, it was superior to TILs and comparable with PD-L1 (AUC, 0.67; 95% CI, 0.60-0.74), with a 10-percentage point improvement in specificity. In the validation cohort, combining the deep learning model with PD-L1 scores achieved an AUC of 0.70 (95% CI, 0.63-0.76), outperforming either marker alone, with a response rate of 51% compared to 41% for PD-L1 (≥50%) alone.

Conclusions and Relevance

The findings of this cohort study demonstrate a strong and independent deep learning-based feature associated with ICI response in patients with NSCLC across various cohorts. Clinical use of this deep learning model could refine treatment precision and better identify patients who are likely to benefit from ICI for treatment of advanced NSCLC.

MAT2A inhibitor AG-270/S095033 in patients with advanced malignancies: a phase I trial

Homozygous MTAP deletion occurs in ~15% of cancers, making them vulnerable to decreases in the concentration of S-adenosylmethionine (SAM). AG-270/S095033 is an oral, potent, reversible inhibitor of methionine adenosyltransferase 2 A (MAT2A), the enzyme primarily responsible for the synthesis of SAM. We report results from the first-in-human, phase 1 trial of AG-270/S095033 as monotherapy in patients with advanced malignancies (ClinicalTrials.gov Identifier: NCT03435250). Eligible patients had tumors with homozygous deletion of CDKN2A/MTAP and/or loss of MTAP protein by immunohistochemistry. Patients received AG-270/S095033 once daily (QD) or twice daily (BID) in 28-day cycles. The primary objective was to assess the maximum tolerated dose (MTD) of AG-270/S095033. Secondary objectives included safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and efficacy. Forty patients were treated with AG-270/S095033. Plasma concentrations of AG-270/S095033 increased with dose. Maximal reductions in plasma SAM concentrations ranged from 54% to 70%. Analysis of paired tumor biopsies showed decreases in levels of symmetrically di-methylated arginine (SDMA) residues. Reversible increases in liver function tests, thrombocytopenia, anemia and fatigue were common treatment-related toxicities. Two partial responses were observed; five additional patients achieved radiographically confirmed stable disease for ≥16 weeks. AG-270/S095033 has a manageable safety profile. Our data provide preliminary evidence of clinical activity and proof-of-mechanism for MAT2A inhibition.

Loss of MTAP expression is strongly linked to homozygous 9p21 deletion, unfavorable tumor phenotype, and noninflamed microenvironment in urothelial bladder cancer

Homozygous 9p21 deletions usually result in a complete loss of S-methyl-5'-thioadenosine phosphorylase (MTAP) expression visualizable by immunohistochemistry (IHC). MTAP deficiency has been proposed as a marker for predicting targeted treatment response. A tissue microarray including 2,710 urothelial bladder carcinomas were analyzed for 9p21 deletion by fluorescence in situ hybridization and MTAP expression by IHC. Data were compared with data on tumor phenotype, patient survival, intratumoral lymphocyte subsets, and PD-L1 expression. The 9p21 deletion rate increased from pTaG2 low (9.2% homozygous, 25.8% heterozygous) to pTaG2 high (32.6%, 20.9%; p < 0.0001) but was slightly lower in pTaG3 (16.7%, 16.7%) tumors. In pT2-4 carcinomas, 23.3% homozygous and 17.9% heterozygous deletions were found, and deletions were tied to advanced pT (p = 0.0014) and poor overall survival (p = 0.0461). Complete MTAP loss was seen in 98.4% of homozygous deleted while only 1.6% of MTAP negative tumors had retained 9p21 copies (p < 0.0001). MTAP loss was linked to advanced stage and poor overall survival in pT2-4 carcinomas (p < 0.05 each). The relationship between 9p21 deletions/MTAP loss and poor patient prognosis was independent of pT and pN (p < 0.05 each). The 9p21 deletions were associated with a noninflamed microenvironment (p < 0.05). Complete MTAP loss is strongly tied to homozygous 9p21 deletion, aggressive disease, and noninflamed microenvironment. Drugs targeting MTAP-deficiency may be useful in urothelial bladder carcinoma. MTAP IHC is a near perfect surrogate for MTAP deficiency in this tumor type.

Context-dependent effects of CDKN2A and other 9p21 gene losses during the evolution of esophageal cancer

CDKN2A is a tumor suppressor located in chromosome 9p21 and frequently lost in Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). How CDKN2A and other 9p21 gene co-deletions affect EAC evolution remains understudied. We explored the effects of 9p21 loss in EACs and cancer progressor and non-progressor BEs with matched genomic, transcriptomic and clinical data. Despite its cancer driver role, CDKN2A loss in BE prevents EAC initiation by counterselecting subsequent TP53 alterations. 9p21 gene co-deletions predict poor patient survival in EAC but not BE through context-dependent effects on cell cycle, oxidative phosphorylation and interferon response. Immune quantifications using bulk transcriptome, RNAscope and high-dimensional tissue imaging showed that IFNE loss reduces immune infiltration in BE, but not EAC. Mechanistically, CDKN2A loss suppresses the maintenance of squamous epithelium, contributing to a more aggressive phenotype. Our study demonstrates context-dependent roles of cancer genes during disease evolution, with consequences for cancer detection and patient management.

The Tumor Metabolite 5'-Deoxy-5'Methylthioadenosine (MTA) Inhibits Maturation and T Cell-Stimulating Capacity of Dendritic Cells

Metabolite accumulation in the tumor microenvironment fosters immune evasion and limits the efficiency of immunotherapeutic approaches. Methylthioadenosine phosphorylase (MTAP), which catalyzes the degradation of 5'-deoxy-5'methylthioadenosine (MTA), is downregulated in many cancer entities. Consequently, MTA accumulates in the microenvironment of MTAP-deficient tumors, where it is known to inhibit tumor-infiltrating T cells and NK cells. However, the impact of MTA on other intra-tumoral immune cells has not yet been fully elucidated. To study the effects of MTA on dendritic cells (DCs), human monocytes were maturated into DCs with (MTA-DC) or without MTA (co-DC) and analyzed for activation, differentiation, and T cell-stimulating capacity. MTA altered the cytokine secretion profile of monocytes and impaired their maturation into dendritic cells. MTA-DCs produced less IL-12 and showed a more immature-like phenotype characterized by decreased expression of the co-stimulatory molecules CD80, CD83, and CD86 and increased expression of the monocyte markers CD14 and CD16. Consequently, MTA reduced the capability of DCs to stimulate T cells. Mechanistically, the MTA-induced effects on monocytes and DCs were mediated by a mechanism beyond adenosine receptor signaling. These results provide new insights into how altered polyamine metabolism impairs the maturation of monocyte-derived DCs and impacts the crosstalk between T and dendritic cells.

MTAP as an emerging biomarker in thoracic malignancies

S-methyl-5'-thioadenosine phosphorylase (MTAP) deficiency is an emerging biomarker in non-small cell lung cancer (NSCLC) and beyond. The MTAP gene is located in the chromosomal region 9p21.3, which shows one of the most common homozygous deletions across all human cancers (9p21 loss). Loss of 9p21 is found in the majority of pleural mesotheliomas, where it serves as an established diagnostic marker. Until recently, fluorescence in situ hybridization (FISH) was the gold standard for the detection of 9p21 losses, but loss of MTAP expression by immunohistochemistry (IHC) gains increasing importance as an easy to apply and cost-effective diagnostic surrogate marker. Besides, MTAP loss, which has been reported in 13% of NSCLC, is becoming an emerging predictive biomarker in two different scenarios in NSCLC and other cancer types: 1) MTAP loss seems to negatively predict the response to immune checkpoint inhibitor (ICI) treatment via silencing of the tumor microenvironment, and 2) MTAP loss serves as a predictive biomarker for novel targeted treatment strategies. MTAP deficiency leads to an impaired function of the protein arginine methyltransferase 5 (PRMT5) due to its partial inhibition by MTAP's accumulating substrate methylthioadenosine (MTA). This process leaves MTAP deficient tumor cells heavily dependent on the remaining function of PRMT5, making it a perfect target for synthetic lethality. Indeed, MTA-cooperative PRMT5-inhibitors are now tested in several clinical trials with promising early results in solid malignancies. With its emergence as a predictive biomarker, the implementation of MTAP IHC into diagnostic routine for NSCLC and other tumors is likely to take place soon. In this review article, we summarize the current literature on the role of MTAP in thoracic tumors and evaluate different testing methods, including IHC, FISH and next generation sequencing.

Prevalence of S-methyl-5'-thioadenosine Phosphorylase (MTAP) Deficiency in Human Cancer: A Tissue Microarray Study on 13,067 Tumors From 149 Different Tumor Types

Loss of S-methyl-5'-thioadenosine phosphorylase (MTAP) expression is a common event in cancer leading to a critical vulnerability of cancer cells towards anti-cancer drugs. Homozygous MTAP deletions result in a complete expression loss that can be detected by immunohistochemistry (IHC). In this study, a tissue microarray containing 17,078 samples from 149 different tumor entities was analyzed by IHC, and complete MTAP loss was validated by fluorescence in situ hybridization. MTAP loss was observed in 83 of 149 tumor categories, including neuroendocrine neoplasms (up to 80%), Hodgkin lymphoma (50.0%), mesothelioma (32.0% to 36.8%), gastro-intestinal adenocarcinoma (4.0% to 40.5%), urothelial neoplasms (10.5% to 36.7%), squamous cell carcinomas (up to 38%), and various types of sarcomas (up to 20%) and non-Hodgkin lymphomas (up to 14%). Homozygous MTAP deletion was found in 90% to 100% of cases with MTAP expression loss in most tumor categories. However, neuroendocrine tumors, Hodgkin lymphomas, and other lymphomas lacked MTAP deletions. MTAP deficiency was significantly linked to unfavorable tumor phenotype in selected tumor entities and the presence of PD-L1 expression on tumor cells, absence of PD-L1 expression on immune cells, and a low density of CD8 + lymphocytes. In summary, MTAP deficiency can occur in various tumor entities and is linked to unfavorable tumor phenotype and noninflamed tumor microenvironment, but is not always related to deletions. MTAP IHC is of considerable diagnostic value for the detection of neoplastic transformation in multiple different applications.

MTA-cooperative PRMT5 inhibitors enhance T cell-mediated antitumor activity in MTAP-loss tumors

BACKGROUND

Hyperactivated protein arginine methyltransferases (PRMTs) are implicated in human cancers. Inhibiting tumor intrinsic PRMT5 was reported to potentiate antitumor immune responses, highlighting the possibility of combining PRMT5 inhibitors (PRMT5i) with cancer immunotherapy. However, global suppression of PRMT5 activity impairs the effector functions of immune cells. Here, we sought to identify strategies to specifically inhibit PRMT5 activity in tumor tissues and develop effective PRMT5i-based immuno-oncology (IO) combinations for cancer treatment, particularly for methylthioadenosine phosphorylase (MTAP)-loss cancer.

METHODS

Isogeneic tumor lines with and without MTAP loss were generated by CRISPR/Cas9 knockout. The effects of two PRMT5 inhibitors (GSK3326595 and MRTX1719) were evaluated in these isogenic tumor lines and T cells in vitro and in vivo. Transcriptomic and proteomic changes in tumors and T cells were characterized in response to PRMT5i treatment. Furthermore, the efficacy of MRTX1719 in combination with immune checkpoint blockade was assessed in two syngeneic murine models with MTAP-loss tumor.

RESULTS

GSK3326595 significantly suppresses PRMT5 activity in tumors and T cells regardless of the MTAP status. However, MRTX1719, a methylthioadenosine-cooperative PRMT5 inhibitor, exhibits tumor-specific PRMT5 inhibition in MTAP-loss tumors with limited immunosuppressive effects. Mechanistically, transcriptomic and proteomic profiling analysis reveals that MRTX1719 successfully reduces the activation of the PI3K pathway, a well-documented immune-resistant pathway. It highlights the potential of MRTX1719 to overcome immune resistance in MTAP-loss tumors. In addition, MRTX1719 sensitizes MTAP-loss tumor cells to the killing of tumor-reactive T cells. Combining MRTX1719 and anti-PD-1 leads to superior antitumor activity in mice bearing MTAP-loss tumors.

CONCLUSION

Collectively, our results provide a strong rationale and mechanistic insights for the clinical development of MRTX1719-based IO combinations in MTAP-loss tumors.

A gut microbiota rheostat forecasts responsiveness to PD-L1 and VEGF blockade in mesothelioma

Malignant mesothelioma is a rare tumour caused by asbestos exposure that originates mainly from the pleural lining or the peritoneum. Treatment options are limited, and the prognosis is dismal. Although immune checkpoint blockade (ICB) can improve survival outcomes, the determinants of responsiveness remain elusive. Here, we report the outcomes of a multi-centre phase II clinical trial (MiST4, NCT03654833) evaluating atezolizumab and bevacizumab (AtzBev) in patients with relapsed mesothelioma. We also use tumour tissue and gut microbiome sequencing, as well as tumour spatial immunophenotyping to identify factors associated with treatment response. MIST4 met its primary endpoint with 50% 12-week disease control, and the treatment was tolerable. Aneuploidy, notably uniparental disomy (UPD), homologous recombination deficiency (HRD), epithelial-mesenchymal transition and inflammation with CD68+ monocytes were identified as tumour-intrinsic resistance factors. The log-ratio of gut-resident microbial genera positively correlated with radiological response to AtzBev and CD8+ T cell infiltration, but was inversely correlated with UPD, HRD and tumour infiltration by CD68+ monocytes. In summary, a model is proposed in which both intrinsic and extrinsic determinants in mesothelioma cooperate to modify the tumour microenvironment and confer clinical sensitivity to AtzBev. Gut microbiota represent a potentially modifiable factor with potential to improve immunotherapy outcomes for individuals with this cancer of unmet need.

Genetically predicted metabolites mediate the association between immune cells and metabolic dysfunction-associated steatotic liver disease: a mendelian randomization study

BACKGROUND

Existing studies have presented limited and disparate findings on the nexus between immune cells, plasma metabolites, and metabolic dysfunction-associated steatotic liver disease (MASLD). The aim of this study was to investigate the causal relationship between immune cells and MASLD. Additionally, we aimed to identify and quantify the potential mediating role of metabolites.

METHODS

A Mendelian randomization (MR) analysis was conducted using two samples of pooled data from genome-wide association studies on MASLD that included 2568 patients and 409,613 control individuals. Additionally, a mediated MR study was employed to quantify the metabolite-mediated immune cell effects on MASLD.

RESULTS

In this study, eight immunophenotypes were linked to the risk of MASLD, and thirty-five metabolites/metabolite ratios were linked to the occurrence of MASLD. Furthermore, a total of six combinations of immunophenotypic and metabolic factors demonstrated effects on the occurrence of MASLD, although the mediating effects of metabolites were not significant.

CONCLUSION

Our study demonstrated that certain immunophenotypes and metabolite/metabolite ratios have independent causal relationships with MASLD. Furthermore, we identified specific metabolites/metabolite ratios that are associated with an increased risk of MASLD. However, their mediating role in the causal association between immunophenotypes and MASLD was not significant. It is important to consider immune and metabolic disorders among patients with MASLD in clinical practice.

Further knowledge and developments in resistance mechanisms to immune checkpoint inhibitors

The past decade has witnessed a revolution in cancer treatment, shifting from conventional drugs (chemotherapies) towards targeted molecular therapies and immune-based therapies, in particular immune-checkpoint inhibitors (ICIs). These immunotherapies release the host's immune system against the tumor and have shown unprecedented durable remission for patients with cancers that were thought incurable, such as metastatic melanoma, metastatic renal cell carcinoma (RCC), microsatellite instability (MSI) high colorectal cancer and late stages of non-small cell lung cancer (NSCLC). However, about 80% of the patients fail to respond to these immunotherapies and are therefore left with other less effective and potentially toxic treatments. Identifying and understanding the mechanisms that enable cancerous cells to adapt to and eventually overcome therapy can help circumvent resistance and improve treatment. In this review, we describe the recent discoveries on the onco-immunological processes which govern the tumor microenvironment and their impact on the resistance to PD-1/PD-L1 checkpoint blockade.

Loss of MTAP Expression by Immunohistochemistry Is a Surrogate Marker for Homozygous 9p21.3 Deletion in Urothelial Carcinoma

Homozygous deletion of the chromosomal region 9p21.3 is common in urothelial carcinoma (UC) and leads to loss of several genes, including CDKN2A and MTAP, resulting in loss of MTAP protein expression. Here, we aimed to explore the diagnostic potential of MTAP immunohistochemistry (IHC) as a surrogate marker for homozygous 9p21.3 deletion (9p21 homozygous deletion [HD]) in UC. MTAP status was determined by IHC on 27 UC tissue specimens with known 9p21.3 status as defined by fluorescence in situ hybridization in matched cytological specimens, by IHC and fluorescence in situ hybridization on a tissue microarray (TMA) containing 359 UC at different stages, and by IHC on 729 consecutive UC from routine practice. Moreover, we analyzed a longitudinal series of matched specimens from 38 patients with MTAP-negative recurrent UC. MTAP loss by IHC was found in all 17 patients with 9p21 HD and in 2/8 cases without 9p21 HD. In the TMA, MTAP loss was more common in metastases (53%) than in muscle-invasive (33%) and non-muscle-invasive UC (29%) (P = .03). In the consecutive series, 164/729 (22%) cases showed loss of MTAP expression. In 41 of these 164 cases (25%), loss of MTAP expression was heterogenous. We also discovered loss of MTAP expression in flat urothelium adjacent to MTAP-negative low-grade UC, suggesting true flat low-grade neoplasia that could not be diagnosed by morphology alone. Longitudinal analysis of recurrences showed persistent negative MTAP status over time in 37/38 (97%) patients. MTAP IHC can serve as a surrogate marker for 9p21 HD in UC and as a diagnostic tool to differentiate reactive urothelium from urothelial neoplasia. It also provides a unique opportunity to study clinicopathological associations and the heterogeneity of 9p21 HD across the whole spectrum of UC manifestations.

Revisiting Treatment of Metastatic Urothelial Cancer: Where Do Cisplatin and Platinum Ineligibility Criteria Stand?

Cisplatin-based chemotherapy has been the standard of care in metastatic urothelial cancer (mUC) for more than two decades. However, many patients with comorbidities cannot receive cisplatin or its alternative, carboplatin. 'Cisplatin-ineligible' and 'platinum-ineligible' patients lacked effective therapy options. However, the recent combination of enfortumab vedotin (EV), an antibody-drug conjugate targeting Nectin-4, with pembrolizumab (P), an antibody targeting the programmed death-1 (PD-1) immune checkpoint, is changing the status quo of frontline mUC treatment, with potential synergy seen in the EV-103 and EV-302 clinical trials. First, we review the working definitions of 'cisplatin ineligibility' and 'platinum ineligibility' in mUC clinical trials and the standard of care in both categories. Then, we review select clinical trials for frontline treatment of cisplatin- and platinum-ineligible mUC patients on ClinicalTrials.gov. We classify the investigated drugs in these trials by their therapeutic strategies. Alongside chemotherapy combinations, the field is witnessing more immunotherapy combinations with fibroblast growth factor receptor (FGFR) inhibitors, bicycle toxin conjugates, bispecific antibodies, innovative targeted therapies, and many others. Most importantly, we rethink the value of classifying patients by cisplatin or platinum ineligibility in the frontline setting in the post-EVP era. Lastly, we discuss new priority goals to tailor predictive, monitoring, and prognostic biomarkers to these emergent therapies.

Tumor cell metabolic reprogramming and hypoxic immunosuppression: driving carcinogenesis to metastatic colonization

A significant factor in the antitumor immune response is the increased metabolic reprogramming of immunological and malignant cells. Increasing data points to the fact that cancer metabolism affects not just cancer signaling, which is essential for maintaining carcinogenesis and survival, but also the expression of immune cells and immune-related factors such as lactate, PGE2, arginine, IDO, which regulate the antitumor immune signaling mechanism. In reality, this energetic interaction between the immune system and the tumor results in metabolic competition in the tumor ecosystem, limiting the amount of nutrients available and causing microenvironmental acidosis, which impairs the ability of immune cells to operate. More intriguingly, different types of immune cells use metabolic reprogramming to keep the body and self in a state of homeostasis. The process of immune cell proliferation, differentiation, and performance of effector functions, which is crucial to the immune response, are currently being linked to metabolic reprogramming. Here, we cover the regulation of the antitumor immune response by metabolic reprogramming in cancer cells and immune cells as well as potential strategies for metabolic pathway targeting in the context of anticancer immunotherapy. We also discuss prospective immunotherapy-metabolic intervention combinations that might be utilized to maximize the effectiveness of current immunotherapy regimes.