Biology subjects

Bohm, M. S.

Publications and source records attributed to Bohm, M. S..

4 recordsLinked to original sources

bioRxiv2024

Determining susceptibility loci in triple negative breast cancer using a novel pre-clinical model

Breast cancer (BC) is the most common cancer and the second cause of death in US women. Our lack of understanding of how genetic variants affect molecular mechanisms that mediate BC aggression poses a substantial obstacle to advancements in cancer diagnosis and therapy. To examine genetic variants on BC traits, a novel murine model was created with robust phenotypic and genomic variation. The FVB C3(1)-T-antigen ("C3Tag") mouse develops spontaneous tumors in the mammary glands of female mice with a mean latency of 4-5 months of age. This genetically engineered mouse model (GEMM) is well established to resemble human basal-like TNBC. TNBC is an aggressive subtype with few clinical approaches and poor patient outcomes. Thus, to model human heterogeneity in BC outcomes, we systematically crossed the C3Tag GEMM into the BXD recombinant inbred family - the largest and best characterized genetic reference population. The new model is termed "BXD-BC" and F1 hybrids of the cross have isogenic genomes that are reproducible. BXD-BCs are a potent tool to determine the impact of genetic modifiers on BC tumor traits. We hypothesized that examination of BXD-BC GEMMs will enable the identification of susceptibility loci, candidate genes, and molecular networks that underlie variation of multiple BC phenotypes. Using N=29 BXD-BC strains, we demonstrated significant heritable variations in the severity of TNBC characteristics such as tumor latency, multiplicity, and survival. Interestingly, 2 BXD-BC strains never developed tumors out to 1 year of age. Thus, BXD-BC strains demonstrate variance in cancer susceptibility and progression compared to the parent C3Tag GEMM, indicating the presence of genetic modifiers. Through an unbiased systematic quantification of breast cancer severity across BXD-BC hybrids, we identified several significant quantitative trait loci (QTL) and candidate genes for specific tumor traits. In combination with public human GWAS datasets, we defined syntenic regions, candidate genes, and underlying networks through cross-species systems genetics analyses to demonstrate the translational validity of conserved, biologically relevant, and targetable candidates. Our findings suggest conserved candidates predicting TNBC patient survival. In sum, the BXD-BC resource is an innovative, reliable, and robust preclinical model that reflects robust genetic heterogeneity. Using cutting edge systems genetics, we have identified genetic modifiers of BC phenotypic variation that could be targeted to advance therapeutic limitations or as biomarkers of risk or response to therapy.

genetics↗

bioRxiv2022

Protein Kinase C Delta Regulates Mononuclear Phagocytes and Hinders Response to Immunotherapy in Cancer

Checkpoint immunotherapy unleashes T cell antitumor potential which has revolutionized cancer treatment showing unprecedented long-term responses. However, most patients do not respond to immunotherapy which often correlates with a dysfunctional or immunosuppressive myeloid compartment. The mononuclear phagocyte system (MPS) is a sub-class of myeloid cells comprising monocytes, macrophages and dendritic cells which plays a crucial role in tissue homeostasis. However, accumulating evidence suggests that mononuclear phagocytes contribute to all phases of tumorigenesis including orchestrating inflammatory events during de novo carcinogenesis, contribution to the progression of established tumors and promotion of resistance to checkpoint blockade. Thus, targeting the MPS could be an effective strategy to enhance checkpoint blockade efficacy and promote control of tumors. Here, we found that protein kinase C delta (PKC{delta}), a serine/threonine kinase, is abundantly expressed by mononuclear phagocytes in several human and mouse tumors. PKC{delta}-/- mice were more resistant to growth of various cancers compared to wild-type mice and were more responsive to anti-PD-1 immunotherapy. Furthermore, we found that tumors from PKC{delta}-/- mice harbor a Th-1-skewed immune landscape including increased antigen cross-presentation and T cell activation. Depletion of mononuclear phagocytes in vivo altered tumor growth in wild-type mice, but not in PKC{delta}-/- mice. In addition, coinjection of PKC{delta}-/--deficient M2-like macrophages with cancer cells into wild-type mice markedly delayed tumor growth and significantly increased intratumoral T cell activation compared to wild-type M2-like macrophages coinjected with cancer cells. Finally, intrinsic loss of PKC{delta}-/- functionally reprogrammed macrophages and dendritic cells by promoting their antigen presenting and cross-presenting capacity and triggered type I and type II interferon signaling. Thus, PKC{delta} might be targeted to reprogram mononuclear phagocytes and augment checkpoint blockade efficacy.

immunology↗

bioRxiv2021

In vitro models of the human esophagus reveal ancestrally diverse response to injury

European Americans (EA) are more susceptible to esophageal tissue damage and inflammation when exposed to gastric acid and bile acid reflux and have a higher incidence of esophageal adenocarcinoma when compared to African Americans (AA). Population studies have implicated specific genes for these differences; however, the underlying cause for these differences is not well understood. We describe a robust long-term culture system to grow primary human esophagus in vitro, use single cell RNA sequencing to compare primary human biopsies to their in vitro counterparts, identify known and new molecular markers of basal cell types, and demonstrate that in vivo cellular heterogeneity is maintained in vitro. We further developed an ancestrally diverse biobank and a high-content, image based, screening assay to interrogate bile-acid injury response. These results demonstrated that AA esophageal cells responded significantly differently than EA-derived cells, mirroring clinical findings, having important implications for addressing disparities in early drug development pipelines.

cell biology↗

bioRxiv2019

Differentiation of Human Colon Tissue In Culture: Effects of calcium on trans-epithelial electrical resistance and tissue cohesive properties

Background and aimsHuman colonoid cultures maintained under low-calcium (0.25 mM) conditions undergo differentiation spontaneously and, concomitantly, express a high level of tight junction proteins, but not desmosomal proteins. When calcium is included to a final concentration of 1.5 - 3.0 mM (provided either as a single agent or as a combination of calcium and minerals), there is little change in tight junction proteins but a strong up-regulation of desmosomal proteins and an increase in desmosome formation. The aim of this study was to assess functional consequences of the differences in calcium-mediated barrier protein expression.\n\nMethodsHuman colonoid-derived epithelial monolayers were interrogated in transwell culture under low- or high-calcium conditions. Ion permeability and monolayer integrity were assessed by measuring trans-epithelial electrical resistance (TEER) across the confluent monolayer. Colonoid cohesiveness was assessed in parallel.\n\nResultsTEER values were high in the low-calcium environment and increased only modestly in response to calcium. In contrast, colonoid cohesiveness increased substantially with calcium supplementation. In both assays, the response to Aquamin was greater than the response to calcium alone. However, differences between interventions were small and only compared to the 0.25 mM calcium were they statistically significant. Consistent with these findings, occludin expression (a measure of tight junctions) was high at 0.25 mM calcium and did not increase with supplementation. Cadherin-17 and desmoglein-2 were weakly-expressed under low calcium conditions but increased with intervention.\n\nConclusionsThese findings indicate that low ambient calcium levels are sufficient to support formation of a permeability barrier in the colonic epithelium. Higher calcium levels are necessary to promote tissue cohesion and enhance barrier function. These findings may help explain how an adequate daily intake of calcium contributes to colonic health by improving barrier function, even though there is little change in colonic histological features over a wide range of calcium intake levels.

physiology↗