Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients.

Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti-programmed cell death 1 protein (PD-1) immunotherapy (n = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (n = 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (P < 0.01) and relative abundance of bacteria of the Ruminococcaceae family (P < 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.

A phase I study of decitabine with pegylated interferon α-2b in advanced melanoma: impact on DNA methylation and lymphocyte populations.

BACKGROUND: Melanoma cell lines treated with decitabine show upregulation of cancer antigens, and interferon-α upregulates MHC Class I antigens in cancer cells, leading to enhanced T-cell recognition and T-cell mediated tumor apoptosis. We evaluated the synergy between the hypomethylating effects of decitabine and the immunomodulatory effects of interferon in a combination regimen administered to advanced melanoma patients in a phase 1 trial. METHODS: Patients with one prior systemic therapy were eligible. Using a modified 3 + 3 design, patients received escalating doses of decitabine and pegylated interferon α-2b (PEG-IFN) during every 28-day treatment cycle. Global DNA methylation was measured on days 1 and 5 of cycles 1 and 3. Cytokine profiling and quantification of T-cell subpopulations by FACS were performed at baseline and cycle 3. RESULTS: Seventeen patients were assigned to one of four dose levels. Decitabine 15 mg/m2/d + PEG-IFN 3 µg/kg was the maximum tolerated dose (MTD). Grade 3/4 cytopenias were seen across all dose levels: anemia (1), neutropenia (7), and thrombocytopenia (2). One patient remained progression-free for 37 weeks. The other 16 patients progressed at or before 12 weeks. Median overall survival was 39 weeks. Hypomethylation was seen at all dose levels. Due to treatment-induced lymphocytopenia, absolute changes in T-cell populations post-treatment were too small to be meaningfully interpreted. CONCLUSIONS: The response to this combination regimen was characterized by significant myelosuppression, particularly neutropenia. Although disappointing efficacy and slow accrual led to early closure of the trial, hypomethylation showed pharmacodynamic evidence of a therapeutic effect of decitabine at all dose levels.

Neoantigen and tumor antigen-specific immunity transferred from immunized donors is detectable early after allogeneic transplantation in myeloma patients.

To enhance the therapeutic index of allogeneic hematopoietic SCT (HSCT), we immunized 10 HLA-matched sibling donors before stem cell collection with recipient-derived clonal myeloma Ig, idiotype (Id), as a tumor antigen, conjugated with keyhole limpet hemocyanin (KLH). Vaccinations were safe in donors and recipients. Donor-derived KLH- and Id-specific humoral and central and effector memory T-cell responses were detectable by day 30 after HSCT and were boosted by post-transplant vaccinations at 3 months in most recipients. One patient died before booster vaccinations. Specifically, after completing treatment, 8/9 myeloma recipients had persistent Id-specific immune responses and 5/9 had improvement in disease status. Although regulatory T cells increased after vaccination, they did not impact immune responses. At a median potential follow-up period of 74 months, 6 patients are alive, the 10 patients have a median PFS of 28.5 months and median OS has not been reached. Our results provide proof of principle that neoantigen and tumor antigen-specific humoral and cellular immunity could be safely induced in HSCT donors and passively transferred to recipients. This general strategy may be used to reduce relapse of malignancies and augment protection against infections after allogeneic HSCT.

Single-column purification of free recombinant proteins using a self-cleavable affinity tag derived from a protein splicing element.

A novel protein purification system has been developed which enables purification of free recombinant proteins in a single chromatographic step. The system utilizes a modified protein splicing element (intein) from Saccharomyces cerevisiae (Sce VMA intein) in conjunction with a chitin-binding domain (CBD) from Bacillus circulans as an affinity tag. The concept is based on the observation that the modified Sce VMA intein can be induced to undergo a self-cleavage reaction at its N-terminal peptide linkage by 1,4-dithiothreitol (DTT), beta-mercaptoethanol (beta-ME) or cysteine at low temperatures and over a broad pH range. A target protein is cloned in-frame with the N-terminus of the intein-CBD fusion, and the stable fusion protein is purified by adsorption onto a chitin column. The immobilized fusion protein is then induced to undergo self-cleavage under mild conditions, resulting in the release of the target protein while the intein-CBD fusion remains bound to the column. No exogenous proteolytic cleavage is needed. Furthermore, using this procedure, the purified free target protein can be specifically labeled at its C-terminus.