Kai W. Wucherpfennig

The cancer-immunity cycle requires cross-presenting type I conventional dendritic cells (cDC1s) that induce T cell–mediated immunity, but therapeutic strategies for enhancing intratumoral cDC1 function are currently inadequate. We found the epigenetic enzyme CARM1 (coactivator-associated arginine methyltransferase 1) to be a selective negative regulator of cancer antigen presentation by cDC1s but not cDC2s. Inactivation of the Carm1 gene promoted cDC1 antigen cross-presentation, activation, and accumulation in tumors, and a CARM1 inhibitor enhanced cDC1-mediated priming of T cells by means of a cancer neoantigen vaccine. CARM1 inhibition increased chromatin accessibility at BATF3-Jun and RelA sites that are critical for cDC1 function and activation. Transforming growth factor–β regulated Carm1 expression, which suggests that CARM1 inactivation enhanced intratumoral cDC1 function without altering cDC1 homeostasis. These studies identify CARM1 as a potential therapeutic target for enhancing the antitumor function of mouse and human cDC1s.

Enriched gene sets in HupT3 cells following TFAP4 knockout and overexpression, generated by the Enrichr search engine

Genome-scale CRISPR-Cas9 screens

Expression of Hallmark IFNγ/IFNα gene sets in HupT3 cells following TFAP4 knockout and overexpression

Catalog of qRT-PCR primers, CRISPR guide sequences, and antibodies used in this study

Differential gene expression in HupT3 cells following TFAP4 knockout and overexpression

Chimeric antigen receptor (CAR) T-cell therapy can lead to dramatic clinical responses in B-cell malignancies. However, early clinical trials with CAR T-cell therapy in non–B-cell malignancies have been disappointing to date, suggesting that tumor-intrinsic features contribute to resistance. To investigate tumor-intrinsic modes of resistance, we performed genome scale CRISPR-Cas9 screens in mesothelin (MSLN)-expressing pancreatic cancer cells. Co-culture with MSLN-targeting CAR T cells identified both antigen-dependent and antigen-independent modes of resistance. In particular, loss of the majority of the genes involved in the pathway responsible for GPI-anchor biosynthesis and attachment abrogated the ability of CAR T cells to target pancreatic cancer cells, suggesting that disruption of this pathway may permit MSLN CAR T-cell evasion in the clinic. Antigen-independent mediators of CAR T-cell response included members of the death receptor pathway as well as genes that regulate tumor transcriptional responses, including TFAP4 and INTS12. TFAP4-mediated CAR T resistance depended on the NFκB transcription factor p65, indicating that tumor resistance to CAR T-cell therapy likely involves alterations in tumor-intrinsic states. Overall, this study uncovers multiple antigen-dependent and -independent mechanisms of CAR T-cell evasion by pancreatic cancer, paving the way for overcoming resistance in this disease that is notoriously refractory to immunotherapy.Significance:The identification and validation of key determinants of CAR T-cell response in pancreatic cancer provide insights into the landscape of tumor cell intrinsic resistance mechanisms and into approaches to improve therapeutic efficacy.

Patients with metastatic high-grade serous ovarian carcinoma are often unresponsive to immunotherapies; here we identify salt-inducible kinases (SIKs) as key drivers of immunosuppression. Human T cells in the presence of patient ascites express high levels of SIK and the upstream kinase LKB1, whereas SIK inhibition reprograms human T cells and strongly activates antitumor responses. In syngeneic mice with resistant high-grade serous ovarian carcinoma, genetic ablation and pharmaceutical inhibition of SIK consistently demonstrated therapeutic efficacy and survival advantages, and combination of PD-1 blockade with SIK inhibition further extended survival. We identified a major role of T cell-intrinsic SIK2 and -3 signaling in driving immunosuppression in part by TXNIP induction and LYST suppression. Multi-omics analyses on SIK inhibitor therapy revealed reduced disease progression, increased T cell infiltration with enhanced cytotoxicity and effector cytokine IFN-γ, and a shift from immunosuppressive to immunostimulatory cellular niche. We propose SIK inhibitors as a new immunotherapy.

This multi-institutional randomized phase II clinical trial (NCT03414684) investigated the efficacy and safety of carboplatin plus nivolumab compared to carboplatin in metastatic triple-negative breast cancer (mTNBC). The primary endpoint was progression-free survival (PFS) in a modified intention-to-treat (mITT) population of patients with chemotherapy-naïve (i.e., first-line) mTNBC. Secondary endpoints included overall survival (OS), confirmed objective response rate, confirmed clinical benefit rate, time to and duration of confirmed objective response, safety, and tolerability. Clinical outcomes were evaluated in the PD-L1-positive subgroup ( ≥ 1% immune cells; SP142 clone) per central review. Biospecimens were collected for correlative analyses. 75 patients were enrolled and treated between 2/2018-9/2020. Among the mITT population (n = 62), median PFS was 4.2 months with carboplatin plus nivolumab vs 5.5 months with carboplatin. Median OS did not significantly differ between arms (16.8 vs 11.1 months, respectively). In PD-L1-positive mTNBC patients (n = 24), median PFS was 8.3 vs 4.7 months; median OS was 17.6 vs 10.7 months. Grade ≥3 adverse events occurred in 56.8% of patients in the combination arm and 65.8% in the carboplatin arm. Carboplatin plus nivolumab did not significantly improve PFS compared to carboplatin in patients overall; however, a trend toward improved outcomes was observed in PD-L1-positive mTNBC patients. High mutational burden, interferon-gamma signaling, early circulating tumor DNA reduction, low baseline serum thymidine kinase activity, and urea cycle dysregulation in the microbiome emerged as potential predictors of response to immune checkpoint inhibitors with platinum.