Gut dysbiosis compromises cancer immunosurveillance by downregulating ileal mucosal addressin cell adhesion molecule 1 (MAdCAM-1), but the metabolic landscape associated with gut dysbiosis remains elusive. Here, we show that antibiotics (ABX) or ABX-associated Enterocloster species lead to the loss of secondary bile acids (BAs) including deoxycholic acid (DCA) and the accumulation of tauro-conjugated primary BAs (tauro-chenodeoxycholic acid [TCDCA] and tauro-β-muricholic acid [T-βMCA]) from the alternative pathway in the plasma of patients and mice. Fecal microbial transplantation (FMT), the ileum-specific farnesoid X receptor (FXR) agonist fexaramine, or glycodeoxycholic acid (GDCA) compensated dysbiosis-associated BA abnormalities and circumvent primary resistance to PD-1 blockade. GDCA curtailed ABX-induced MAdCAM-1 downregulation and T cell exhaustion in tumors. Subclinical cholestasis defined by elevation of γ-glutamyl transferase (γGT) correlated with increased TCDCA and decreased soluble MAdCAM-1 in plasma and predicted poor survival in multivariate analyses in six cohorts of patients who received immunotherapy. Hence, subclinical cholestasis accompanies gut dysbiosis, paving the way to immunoresistance.

Allogeneic CAR-engineered NK cells enable scalable off-the-shelf therapy, yet donor heterogeneity remains a major barrier to consistent potency. Building on our clinical experience with cord blood-derived CAR NK cells, we identified an immature CD16[-]CD161[-] double-negative (DN) NK subset associated with poor outcomes. Following CAR engineering, DN-derived NK cells remained hypofunctional yet exhibited exaggerated trogocytosis, accumulating high levels of cognate antigen and forming an intra-product trogocytic-antigen sink (TAS) that diverted CAR engagement from tumor targets and promoted on-target off-tumor interactions within the product. Consequently, CD16[+]CD161[+] double-positive (DP) effectors exposed to the TAS underwent sustained activation, metabolic stress, fratricide, reduced viability, programmed cell death, and progressive exhaustion, culminating in impaired persistence and tumor control. Pre-manufacturing DN depletion eliminated the TAS and restored DP antitumor activity across hematologic and solid tumor models. Together, these findings define a donor subset-driven mechanism of CAR NK dysfunction and provide a manufacturing strategy to improve antitumor potency.

Antibiotics compromise the efficacy of immune checkpoint inhibition (ICI) therapy in cancer, but the underlying mechanism remains unclear. In this issue of Cancer Cell, Mallard de La Varende et al. identify dysbiosis-associated tauro-conjugated bile acids as drivers of ICI non-response and γ-glutamyl transferase (γGT) as a predictive biomarker.

Tumor-infiltrating plasma cells are key responders to immunotherapy. In this issue of Cancer Cell, Meyerhoff et al. show that plasma cells from lung lesions of anti-PD-1-treated patients target citrullinated proteins. Engineering CAR T cells with these plasma cells scFv reveals anti-tumor specificity without adverse effects, identifying therapeutic opportunities.

The role of tumor-infiltrating B cells (TIL-Bs) in shaping anti-tumor responses in the context of immune checkpoint blockade remains incompletely understood. Here, we interrogate the humoral response in resected lung tumors from patients with non-small cell lung cancer (NSCLC) treated with neoadjuvant PD-1 blockade. We find that tumors orchestrate tertiary lymphoid structures with CD138[+] plasma cells, from which we clone recombinant monoclonal antibodies (mAbs) using B cell receptors (BCRs) exhibiting somatic hypermutation and class switching. Several mAbs bind cell-surface citrullinated proteins, characteristic of cancer cells. Chimeric antigen receptor (CAR) T redirected with the soluble chain fragment variable (scFv) of our lead candidate antibody (PC-1) specifically target tumor cells and tumor-promoting myeloid cells in vivo without off-target activity. Moreover, ablation of the citrullination enzyme PADI2 in tumor-bearing mice eliminates reactivity to PC-1 and cytotoxic killing by the CAR. Our results implicate a therapeutic potential for tumor-infiltrating plasma cells that may be harnessed for cancer treatment.

Nerves and cancer-associated fibroblasts (CAFs) have each been shown to regulate cancer progression directly. However, whether these cells interact to control tumor progression remains largely unknown. We show that in colorectal cancer (CRC), cholinergic stimulation induces CHRM3/Gq-dependent NTN1 secretion from CAFs, which in turn enhances intratumor cholinergic innervation. Within this feedforward loop, cholinergic stimulation promotes CRC growth directly through tumoral CHRM3/Gq-mediated YAP activation, while CAF-derived NTN1 promotes CRC growth and epithelial-to-mesenchymal transition-like programs via UNC5B-PI3K/AKT signaling. Chemogenetic activation of cholinergic neurons or fibroblast activation of the M3 receptor/Gq promotes tumoral YAP and AKT signaling and CRC progression. Conversely, blocking CHRM3 or NTN1 suppresses these pathways and improves mouse survival. In human CRC, high NTN1 expression is associated with a mesenchymal-like subtype and poor patient outcomes. These findings suggest that the neuro-mesenchymal interaction is central to CRC progression and could be therapeutically targeted with a CHRM3 antagonist or NTN1-blocking antibody.

The prevailing notion is that effector T cell activation mediates anti-PD-1 efficacy in cancer. Here, we conducted a mechanistic study parallel to our phase 2 trial of perioperative anti-PD-1 therapy in patients with resectable recurrent hepatocellular carcinoma (HCC) (NCT04615143) to study its mechanism of action. Late-recurrence patients present two distinct subtypes characterized by T cell or B cell dominant responses in the tumor microenvironment by dynamic single-cell multi-omics analysis. Clonal antibody repertoire analysis and spatially paired scRNA-seq/BCR-seq reveal somatic hypermutation promoting antibody binding against hepatitis B virus core antigen (HBcAg) within tumor tertiary lymphoid structures (TLSs) in these type B-late recurrence patients. Mechanistically, HBcAg is exported into the extracellular space, triggering local B cell and antibody responses and complement activation. In mice, these high-affinity HBcAg-reactive antibodies lead to complement-mediated antitumor activity with enhanced anti-PD-1 efficacy. Thus, we uncover enhanced anti-virus B cell immunity within the TLS as a mechanism to anti-PD-1 in HCC.

Perioperative immunotherapy improves outcomes in locally advanced gastric or gastroesophageal junction cancer (GC/GEJC), but reliable predictive biomarkers remain elusive. In this biomarker-stratified, randomized, multicenter phase 2 Mountain-02 trail (NCT06374901), 136 patients with operable cT3-4aN + M0 GC/GEJC were enrolled and stratified by tumor-specific MHC class II (tsMHC-II) expression status and then randomized (1:1) to receive perioperative tislelizumab plus chemotherapy or chemotherapy alone. Among tsMHC-II-positive patients, adding tislelizumab to chemotherapy significantly increased the major pathological response (mPR) rate compared with chemotherapy alone (61.8% vs. 26.5%, p = 0.003), meeting the pre-specified primary endpoint. In contrast, no significant benefit was observed in the tsMHC-II-negative subgroup. Within the combination therapy arm, tsMHC-II-positive patients also achieved numerically higher mPR (61.8% vs. 23.5%, p = 0.001) and higher pathological complete response (pCR) rate (32.4% vs. 5.9%, p = 0.006) than tsMHC-II-negative patients. These findings support tsMHC-II as a promising predictive biomarker for perioperative immunotherapy and warrant further validation in larger studies.

In this issue of Cancer Cell, Vuong et al. perform a cross-species functional and molecular analysis of the mechanisms of response and adaptation to VEGFR kinase inhibitors and immunotherapy, identifying SPP1+ tumor-associated macrophages as key players of response to therapy. They further demonstrate that chronic treatment promotes metastatic spread.

Severe thrombocytopenia is a known complication of menin inhibitor therapy; however, the mechanism underlying this effect is unknown. In this issue of Cancer Cell, Wen et al. demonstrate that menin is a key component of normal megakaryopoiesis and establish menin as a therapeutic vulnerability in myeloproliferative neoplasms.

Tertiary lymphoid structures (TLSs) correlate with favorable responses to immune checkpoint inhibitors (ICIs) in various cancers, yet many patients with TLS-positive tumors are resistant to treatment. Multi-omic profiling of clear cell renal cell carcinoma (ccRCC) and soft tissue sarcoma tumors (STSs) reveals an upregulation of gamma-aminobutyric acid (GABA)-related signatures in non-responders to ICIs. In ccRCC, TLSs from non-responders located near GABA-producing tumor cells exhibit impaired B cell maturation, reduced IgG production, higher GABA receptor expression, and tricarboxylic acid cycle activation. In vitro, exposure of human B cells to GABA reduces HLA-DR expression, proliferation, and immunoglobulin secretion by receptor-independent and dependent mechanisms. Pharmacological inhibition of GABA-synthesis increases ICI response and immune infiltration, particularly by B cells, in a TLS-positive STS mouse model. Our findings unravel GABA as an immunoregulatory metabolite and provide a rationale for its therapeutic targeting to overcome ICI resistance in patients with TLS-positive tumors.

Menin inhibition, an approved therapy for KMT2A-rearranged and NPM1 mutant acute leukemia, is accompanied by decreased platelet counts in 15-20% of heavily pre-treated patients. While studying the mechanism underlying this effect, we discovered that menin inhibition reduced the numbers of megakaryocyte progenitors in human CD34[+] cultures and in mice. Because megakaryocytes are key drivers of myeloproliferative neoplasms (MPNs), we investigated the extent to which menin inhibition ameliorates MPN phenotypes. We found that the menin inhibitor revumenib has potent anti-tumor activity, synergizes with ruxolitinib, and shows only subtle effects on healthy mice. Moreover, revumenib suppressed megakaryopoiesis of primary MPN patient specimens in vitro and in vivo. Importantly, genetic knockout of MEN1 and its target MEF2C phenocopied the action of revumenib, confirming an on-target effect of the drug. Together, we reveal menin as a dependency in proliferative megakaryocytes and support further evaluation of menin inhibition as a potential therapy for MPNs.