Darren S. Sigal

Background: Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) mediate cancer immune suppression by promoting an immunosuppressive microenvironment that inhibits effective anti-tumor immunity. However, they are still a poorly understood, heterogeneous mix of neutrophil subsets. This study aims to determine the Siglec expression profile on several neutrophil subsets and assess their immunosuppressive ability.Methods: We identified CD16^high and CD16^low neutrophil subsets from the low-density fractions of human peripheral blood and compared them to high-density neutrophils. We profiled the expression of the entire family of Siglecs on these three key neutrophil populations under steady-state conditions in healthy subjects as well as cancer patients. Moreover, the ability of these populations, isolated from healthy subjects, to suppress T cell proliferation was assessed.Results: Two distinct subpopulations were investigated within the low-density fraction of human peripheral blood (CD15⁺CD66b⁺CD16^low and CD15⁺CD66b⁺CD16^high) and compared to high-density neutrophils (CD15⁺CD66b⁺CD16^high). We found that in addition to CD33 (Siglec-3), Siglec-5/-14, -7, and -9, are differentially expressed on the CD16^low and CD16^high low-density subsets in both healthy, steady-state subjects, and cancer patients. Upregulated expression of CD33 on the CD16^low cells led to the initial speculation that they are MDSCs. As the differential expression of Siglec-9 between these two populations was striking, we used CD16 and Siglec-9 double staining to quantify these populations, which demonstrated that the CD16^lowSiglec-9^low population is greatly upregulated in cancer patients. The CD16^high low-density and high-density neutrophils, but not the CD16^low low-density neutrophils from healthy subjects, inhibited T cell proliferation, indicating that the CD16^lowSiglec-9^low population are not MDSCs.Conclusions: These results demonstrate that Siglecs are differentially expressed on neutrophil subsets, and along with CD16, may be used to help further define what is a PMN-MDSC. Consistent with current observations by others, PMN-MDSCs may encompass an array of neutrophil subtypes, including low-density neutrophils, and point to the need for more work to precisely define the genetic signatures of PMN-MDSCs.

E15608 Background: Molecular characterization by next-generation sequencing (NGS) has been unable to detect pathogenic driver mutations in a significant number of tumors. For example, 40% of colorectal carcinomas (CRC) are RAS and BRAF wild-type and do not have therapeutic targets after comprehensive molecular characterization using FISH, IHC and NGS. Analysis of 3D genomics data produced by DNA-based chromosome conformation capture (Hi-C) assay has been shown to detect gene fusions and other rearrangements in tumor biopsies. We applied Hi-C in a cohort of CRC tumors previously characterized using FISH, IHC, whole exome sequencing (WES) and whole transcriptome sequencing (WTS) by a large commercial reference laboratory, where no targets had been reported, to evaluate the potential for Hi-C to identify novel therapeutic targets. Methods: FFPE tissue from 14 CRC tumors were subjected to Hi-C using the Arima HiC+ for FFPE kit. Hi-C libraries were sequencing to ~100M raw read-pairs on an Illumina NovaSeq, and fusions were called using the Arima-SV pipeline. To attribute clinical significance, we characterized fusions based on whether the fusion event involved a Tier 1 therapeutic level biomarker or a Tier 3 diagnostic or prognostic biomarker according to NCCN and OncoKb, or a Tier 2 biomarker if the biomarker was the target of a therapy in an ongoing clinical trial. Results: Hi-C detected fusions implicating a Tier 1 biomarker in 50% (7/14) of tumors, a Tier 2 level biomarker in 14% (2/14), and a Tier 3 level biomarker in 14% (2/14). Homologous recombination repair (HRR) gene rearrangements were detected in 29% (n = 4/14) of CRC tumors, disrupting HRR genes ( BRIP1, BRCA1, BRCA2, RAD51D). NRG1 gene fusions were detected in 14% (2/14), and amplified complex rearrangement carrying KRAS was detected in one CRC case. A complex rearrangement involving extrachromosomal DNA (ecDNA) amplification carrying EGFR was detected in two cases that were both previously found to have EGFR amplifications, but the ecDNA nature was not previously known and was confirmed by FISH. Lastly, Hi-C detected gene rearrangements involving POLE or APC in two CRC cases, alterations in which are known to increase risk for colonic polyposis. Conclusions: Fusion detection by Hi-C in CRC may uncover numerous therapeutic biomarkers not currently detected by molecular profiling. Our data suggests that homologous recombination deficiency (HRD) may frequently result from HRR gene rearrangements readily detectable by Hi-C, and this alternate mechanism for HRD may serve as a therapeutic biomarker for HRD directed therapies. Our data also suggests that therapeutically targetable gene fusions and complex rearrangements involving therapeutic level biomarkers are also readily detectable by Hi-C, detection of which may increase the number of CRC patients treatable with targeted therapies.

Glycans, chains of sugar molecules found conjugated to cell proteins and lipids, contribute to their growth, movement and differentiation. Aberrant glycosylation is a hallmark of several medical co... Tweetable abstract There is an opportunity to utilize anti-Globo H and anti-SSEA-4 agents both as monotherapy and in combination with immune checkpoint inhibitors. It is hoped that these agents wil...

Programmed cell death protein-1 (PD-1) is an immune checkpoint receptor that induces and maintains tolerance of T cells, invariant natural killer T (iNKT) cells, and natural killer (NK) cells, among other lymphocytes. Immune checkpoint inhibition by PD-1 blockade restores the lymphocytic immunostimulatory phenotype and has been successful in the treatment of various malignancies. However, while immune checkpoint blockade has been shown to provide robust antitumor treatment outcomes, its overall response rate remains low in a significant portion of cancer patients. An essential unmet need in cancer therapy is the development of novel pharmacologic strategies designed to lower rates of resistance associated with immune checkpoint blockade. Therefore, efforts that seek to enhance the efficacy of PD-1 inhibition possess profound immunotherapeutic potential. Here, three promising combination strategies that harness the antitumor effects of immune checkpoint inhibitors (ICIs) together with non-ICI antitumor therapeutic agents are reviewed. These agents include (1) ABX196, a potent inducer of iNKT cells, (2) chimeric antigen receptor (CAR)-T cell therapy, and (3) NK cell therapy. A comprehensive literature search was conducted using the PubMed and ClinicalTrials.gov databases for scientific articles and active trials, respectively, pertaining to immune checkpoint inhibition, iNKT cells, CAR-T cells, and NK cell immunotherapy. Preliminary clinical and preclinical data suggest that these combination treatment regimens greatly suppress tumor growth and may serve as innovative methods to enhance and optimize anticancer immunotherapy.

In this review, we highlight the pre-clinical development, recent clinical studies, and future directions of larotrectinib in patients with NTRK fusion-positive tumors.

Checkpoint inhibitor therapy has introduced a revolution in contemporary anticancer therapy. It has led to dramatic improvements in patient outcomes and has spawned tremendous research into novel immunomodulatory agents and combination therapy that has changed the trajectory of cancer care. However, clinical benefit in patients with colorectal cancer has been generally limited to tumors with loss of mismatch repair function and those with specific germline mutations in the DNA polymerase gene. Unfortunately, tumors with these specific mutator phenotypes are in the minority. Recent pre-clinical and clinical studies have begun to reveal encouraging results suggesting that checkpoint inhibitor therapy can be expanded to an increasing number of colorectal tumors with microsatellite stability and the absence of traditional predictive biomarkers of checkpoint inhibitor response. These studies generally rely on combinations of checkpoint inhibitors with chemotherapy, molecular targeted therapy, radiation therapy, or other novel immunomodulatory agents. This article will review the most current data in microsatellite stable colorectal cancer.

Comprehensive genomic profiling identifies novel NTRK fusions in neuroendocrine tumors Comprehensive genomic profiling identifies novel NTRK fusions in neuroendocrine tumors

Introduction: Hyaluronan (HA) accumulation in the tumor microenvironment produces elevated tumor pressure, vascular compression, and reduced drug delivery. PEGPH20 degrades HA, increasing the access and therapeutic index of anticancer agents.

The dramatic success of immune checkpoint inhibitors (ICIs) in metastatic melanoma and non-small cell lung cancer (NSCLC) has made them a cornerstone in the therapeutic armamentarium of these malignancies. However, the role of these immunomodulating agents in the spectrum of gastrointestinal (GI) tumors has only recently come into focus. Pre-clinical studies have demonstrated up-regulation of checkpoint molecules [i.e., programmed death-ligand 1 (PD-L1)] and increased somatic mutations in select GI tumors, making checkpoint blockade potentially effective. In the clinical setting, patients with microsatellite instability high (MSI-high) and PD-L1 positive gastric and esophageal cancer have shown pronounced responses to single-agent administration of checkpoint antibodies. More recently, responses have also been seen in subsets of patients with biliary and anal cancer. Furthermore, novel immunotherapeutic strategies have been employed in patients with pancreatic cancer and microsatellite stable colorectal cancer (CRC) with preliminary success. Despite current limitations of small sample sizes, highly anticipated prospective data are expected to accrue in the coming years. Finding new combination strategies and predictive biomarkers of response will be critical in optimizing efficacy of these agents and ensuring the highest likelihood of benefit. In this review, we will explore key clinical trials that investigate ICIs alone or in combination with additional chemotherapy, radiotherapy or immunotherapy in patients with gastric, esophageal, colorectal, pancreas, biliary and anal cancer.