Charge-based interactions through peptide position 4 drive diversity of antigen presentation by human leukocyte antigen class I molecules

Human leukocyte antigen class I (HLA-I) molecules bind and present peptides at the cell surface to facilitate the induction of appropriate CD8+ T cell-mediated immune responses to pathogen- and self-derived proteins. The HLA-I peptide-binding cleft contains dominant anchor sites in the B and F pockets that interact primarily with amino acids at peptide position 2 and the C-terminus, respectively. Nonpocket peptide-HLA interactions also contribute to peptide binding and stability, but these secondary interactions are thought to be unique to individual HLA allotypes or to specific peptide antigens. Here, we show that two positively charged residues located near the top of peptide-binding cleft facilitate interactions with negatively charged residues at position 4 of presented peptides, which occur at elevated frequencies across most HLA-I allotypes. Loss of these interactions was shown to impair HLA-I/peptide binding and complex stability, as demonstrated by both in vitro and in silico experiments. Furthermore, mutation of these Arginine-65 (R65) and/or Lysine-66 (K66) residues in HLA-A*02:01 and A*24:02 significantly reduced HLA-I cell surface expression while also reducing the diversity of the presented peptide repertoire by up to 5-fold. The impact of the R65 mutation demonstrates that nonpocket HLA-I/peptide interactions can constitute anchor motifs that exert an unexpectedly broad influence on HLA-I-mediated antigen presentation. These findings provide fundamental insights into peptide antigen binding that could broadly inform epitope discovery in the context of viral vaccine development and cancer immunotherapy.

Interleukin-6 blockade abrogates immunotherapy toxicity and promotes tumor immunity

Immune checkpoint blockade (ICB) therapy frequently induces immune-related adverse events. To elucidate the underlying immunobiology, we performed a deep immune analysis of intestinal, colitis, and tumor tissue from ICB-treated patients with parallel studies in preclinical models. Expression of interleukin-6 (IL-6), neutrophil, and chemotactic markers was higher in colitis than in normal intestinal tissue; T helper 17 (Th17) cells were more prevalent in immune-related enterocolitis (irEC) than T helper 1 (Th1). Anti-cytotoxic T-lymphocyte-associated antigen 4 (anti-CTLA-4) induced stronger Th17 memory in colitis than anti-program death 1 (anti-PD-1). In murine models, IL-6 blockade associated with improved tumor control and a higher density of CD4+/CD8+ effector T cells, with reduced Th17, macrophages, and myeloid cells. In an experimental autoimmune encephalomyelitis (EAE) model with tumors, combined IL-6 blockade and ICB enhanced tumor rejection while simultaneously mitigating EAE symptoms versus ICB alone. IL-6 blockade with ICB could de-couple autoimmunity from antitumor immunity.

IL-1α Mediates Innate and Acquired Resistance to Immunotherapy in Melanoma

Inflammation has long been associated with cancer initiation and progression; however, how inflammation causes immune suppression in the tumor microenvironment and resistance to immunotherapy is not well understood. In this study, we show that both innate proinflammatory cytokine IL-1α and immunotherapy-induced IL-1α make melanoma resistant to immunotherapy. In a mouse melanoma model, we found that tumor size was inversely correlated with response to immunotherapy. Large tumors had higher levels of IL-1α, Th2 cytokines, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), and regulatory T cells but lower levels of IL-12, Th1 cytokines, and activated T cells. We found that therapy with adenovirus-encoded CD40L (rAd.CD40L) increased tumor levels of IL-1α and PMN-MDSCs. Blocking the IL-1 signaling pathway significantly decreased rAd.CD40L-induced PMN-MDSCs and their associated PD-L1 expression in the tumor microenvironment and enhanced tumor-specific immunity. Similarly, blocking the IL-1 signaling pathway improved the antimelanoma activity of anti-PD-L1 Ab therapy. Our study suggests that blocking the IL-1α signaling pathway may increase the efficacy of immunotherapies against melanoma.

Endometrial biomarkers in premenopausal women with obesity: an at-risk cohort

BACKGROUND

Obesity is a well-known risk factor for endometrial cancer, but the mechanisms of obesity-related carcinogenesis are not well defined, particularly for premenopausal women. With the continuing obesity epidemic, increases in the incidence of endometrial cancer and a younger age of diagnosis are often attributed to a hyperestrogenic state created by hormone production in adipose tissue, but significant knowledge gaps remain. The balance of estrogen-responsive signals has not been defined in the endometrium of premenopausal women with obesity, where obesity may not create hyperestrogenism in the context of ovaries being the primary source of estrogen production. Obesity is associated with a state of low-grade, chronic inflammation that can promote tumorigenesis, and it is also known that hormonal changes alter the immune microenvironment of the endometrium. However, limited research has been conducted on endometrial immune-response changes in women who have an increased risk for cancer due to obesity.

OBJECTIVE

Endometrial estrogen-regulated biomarkers, previously shown to be dysregulated in endometrial cancer, were evaluated in a cohort of premenopausal women to determine if obesity is associated with differences in the biomarker expression levels, which might reflect an altered risk of developing cancer. The expression of a multiplexed panel of immune-related genes was also evaluated for expression differences related to obesity.

STUDY DESIGN

Premenopausal women with a body mass index of ≥30 kg/m² (n=97) or a body mass index of ≤25 kg/m² (n=33) were prospectively enrolled in this cross-sectional study, which included the assessment of serum metabolic markers and a timed endometrial biopsy for pathologic evaluation, hormone-regulated biomarker analysis, and immune response gene expression analysis. Medical and gynecologic histories were obtained. Endometrial gene expression markers were also compared across the body mass index groups in a previous cohort of premenopausal women with an inherited cancer risk (Lynch syndrome).

RESULTS

In addition to known systemic metabolic differences, histologically normal endometria from women with obesity showed a decrease in gene expression of progesterone receptor (P=.0027) and the estrogen-induced genes retinaldehyde dehydrogenase 2 (P=.008), insulin-like growth factor 1 (P=.016), and survivin (P=.042) when compared with women without obesity. The endometrial biomarkers insulin-like growth factor 1, survivin, and progesterone receptor remained statistically significant in multivariate linear regression models. In contrast, women with obesity and Lynch syndrome had an increased expression of insulin-like growth factor 1 (P=.017). There were no differences in endometrial proliferation, and limited endometrial immune differences were observed.

CONCLUSION

When comparing premenopausal women with and without obesity in the absence of endometrial pathology or an inherited cancer risk, the expression of the endometrial biomarkers does not reflect a local hyperestrogenic environment, but it instead reflects a decreased cancer risk profile that may be indicative of a compensated state. In describing premenopausal endometrial cancer risk, it may be insufficient to attribute a high-risk state to obesity alone; further studies are warranted to evaluate individualized biomarker profiles for differences in the hormone-responsive signals or immune response. In patients with Lynch syndrome, the endometrial biomarker profile suggests that obesity further increases the risk of developing cancer.

Macrophage depletion through colony stimulating factor 1 receptor pathway blockade overcomes adaptive resistance to anti-VEGF therapy

Anti-angiogenesis therapy has shown clinical benefit in patients with high-grade serous ovarian cancer (HGSC), but adaptive resistance rapidly emerges. Thus, approaches to overcome such resistance are needed. We developed the setting of adaptive resistance to anti-VEGF therapy, and performed a series of in vivo experiments in both immune competent and nude mouse models. Given the pro-angiogenic properties of tumor-associated macrophages (TAMs) and the dominant role of CSF1R in macrophage function, we added CSF1R inhibitors following emergence of adaptive resistance to anti-VEGF antibody. Mice treated with a CSF1R inhibitor (AC708) after anti-VEGF antibody resistance had little to no measurable tumor burden upon completion of the experiment while those that did not receive a CSF1R inhibitor still had abundant tumor. To mimic clinically used regimens, mice were also treated with anti-VEGF antibody and paclitaxel until resistance emerged, and then a CSF1R inhibitor was added. The addition of a CSF1R inhibitor restored response to anti-angiogenesis therapy, resulting in 83% lower tumor burden compared to treatment with anti-VEGF antibody and paclitaxel alone. Collectively, our data demonstrate that the addition of a CSF1R inhibitor to anti-VEGF therapy and taxane chemotherapy results in robust anti-tumor effects.

Macrophage depletion through colony stimulating factor 1 receptor pathway blockade overcomes adaptive resistance to anti-VEGF therapy

Anti-angiogenesis therapy has shown clinical benefit in patients with high-grade serous ovarian cancer (HGSC), but adaptive resistance rapidly emerges. Thus, approaches to overcome such resistance are needed. We developed the setting of adaptive resistance to anti-VEGF therapy, and performed a series of in vivo experiments in both immune competent and nude mouse models. Given the pro-angiogenic properties of tumor-associated macrophages (TAMs) and the dominant role of CSF1R in macrophage function, we added CSF1R inhibitors following emergence of adaptive resistance to anti-VEGF antibody. Mice treated with a CSF1R inhibitor (AC708) after anti-VEGF antibody resistance had little to no measurable tumor burden upon completion of the experiment while those that did not receive a CSF1R inhibitor still had abundant tumor. To mimic clinically used regimens, mice were also treated with anti-VEGF antibody and paclitaxel until resistance emerged, and then a CSF1R inhibitor was added. The addition of a CSF1R inhibitor restored response to anti-angiogenesis therapy, resulting in 83% lower tumor burden compared to treatment with anti-VEGF antibody and paclitaxel alone. Collectively, our data demonstrate that the addition of a CSF1R inhibitor to anti-VEGF therapy and taxane chemotherapy results in robust anti-tumor effects.