Faculty Bibliography

Some cells discard undesired inherited components in bulk by forming large compartments that are subsequently eliminated. Caenorhabditis elegans primordial germ cells (PGCs) jettison mitochondria and cytoplasm by forming a large lobe that is cannibalized by intestinal cells. Although PGCs are nonmitotic, we find that lobe formation is driven by constriction of a contractile ring and requires the RhoGEF ECT-2, a RhoA activator also essential for cytokinesis. Whereas centralspindlin activates ECT-2 to promote cytokinetic contractile ring formation, we show that the ECT-2 regulator NOP-1, but not centralspindlin, is essential for PGC lobe formation. We propose that lobe contractile ring formation is locally inhibited by the PGC nucleus, which migrates to one side of the cell before the cytokinetic ring assembles on the opposite cortex. Our findings reveal how components of the cytokinetic contractile ring are reemployed during interphase to create compartments used for cellular remodeling, and they reveal differences in the spatial cues that dictate where the contractile ring will form.

Addressing the complexity of organogenesis at a system-wide level requires a complete understanding of adult cell types, their origin, and precursor relationships. The Drosophila ovary has been a model to study how coordinated stem cell units, germline, and somatic follicle stem cells maintain and renew an organ. However, lack of cell type-specific tools have limited our ability to study the origin of individual cell types and stem cell units. Here, we used a single-cell RNA sequencing approach to uncover all known cell types of the developing ovary, reveal transcriptional signatures, and identify cell type-specific markers for lineage tracing. Our study identifies a novel cell type corresponding to the elusive follicle stem cell precursors and predicts subtypes of known cell types. Altogether, we reveal a previously unanticipated complexity of the developing ovary and provide a comprehensive resource for the systematic analysis of ovary morphogenesis.

After mastectomy, breast reconstruction is increasingly performed using autologous tissue with the aim of improving quality of life. During this procedure, autologous tissue is excised, relocated, and reattached using vascular anastomoses at the site of the extirpated breast. The period during which the tissue is ex vivo may allow genetic modification without any systemic exposure to the vector. Could such access be used to deliver therapeutic agents using the tissue flap as a vehicle? Such delivery may be more efficient than systemic treatment, in terms of oncological outcomes. The cytokine interferon gamma (IFNγ) has antitumor effects, but systemic toxicity that could be circumvented if its effect can be localized by delivery of the IFNγ gene via gene therapy to autologous tissue used for breast reconstruction, which then releases IFNγ and exerts anti-tumor effects. In a rat model of loco-regional recurrence (LRR) using both MADB-106-Luc and MAD-MB-231-Luc breast cancer cells, autologous tissue was transduced ex vivo with an adeno-associated viral vector (AAV) encoding IFNγ. The therapeutic reconstruction released IFNγ at the LRR site and eliminated cancer cells, significantly decreased tumor burden (P<0.05), and increased survival by 33% (P<0.05) compared to sham reconstruction. Mechanistically, localized IFNγ immunotherapy stimulated M1 macrophages to target cancer cells within the regional confines of the modified tumor environment. This concept of therapeutic breast reconstruction using ex vivo gene therapy of autologous tissue offers a new application for immunotherapy in breast cancer with a dual therapeutic effect of both reconstructing the ablative defect and delivering local adjuvant immunotherapy.

Metformin, the world's most prescribed anti-diabetic drug, is also effective in preventing type 2 diabetes in people at high risk^1,2. Over 60% of this effect is attributable to the ability of metformin to lower body weight in a sustained manner³. The molecular mechanisms by which metformin lowers body weight are unknown. In two, independent randomised controlled clinical trials, circulating levels of GDF15, recently described to reduce food intake and lower body weight through a brain stem-restricted receptor, were increased by metformin. In wild-type mice, oral metformin increased circulating GDF15 with GDF15 expression increasing predominantly in the distal intestine and the kidney. Metformin prevented weight gain in response to a high-fat diet in wild-type mice but not in mice lacking GDF15 or its receptor GFRAL. In obese, high-fat-fed mice, the effects of metformin to reduce body weight were reversed by a GFRAL antagonist antibody. Metformin had effects on both energy intake and energy expenditure that required GDF15. Metformin retained its ability to lower circulating glucose levels in the absence of GDF15 action. In summary, metformin elevates circulating levels of GDF15, which are necessary for its beneficial effects on energy balance and body weight, major contributors to its action as a chemopreventive agent.

The recruitment and activation of inflammatory cells in the liver delineates the transition from hepatic steatosis to steatohepatitis. We found that in steatohepatitis, γδT cells are recruited to the liver by CCR2, CCR5, and NOD2 signaling and are skewed towards an IL-17A⁺ phenotype in an ICOS-ICOSL dependent manner. γδT cells exhibit a distinct Vγ4⁺ , PD1⁺ , Ly6C⁺ CD44⁺ phenotype in steatohepatitis. Moreover, γδT cells upregulate both CD1d, which is necessary for lipid-based antigens presentation, and the free fatty acid receptor CD36. γδT cells are stimulated to express IL-17A by palmitic acid and CD1d ligation. Deletion, depletion, and targeted interruption of γδT cell recruitment protects against diet-induced steatohepatitis and accelerates disease resolution. We demonstrate that hepatic γδT cells exacerbate steatohepatitis, independent of IL-17 expression, by mitigating conventional CD4⁺ T cell expansion and modulating their inflammatory program via CD1d-dependent VEGF expression.

Despite substantial progress in lung cancer immunotherapy, the overall response rate in KRAS-mutant lung adenocarcinoma (ADC) patients remains low. Combining standard immunotherapy with adjuvant approaches that enhance adaptive immune responses-such as epigenetic modulation of anti-tumor immunity-is therefore an attractive strategy. To identify epigenetic regulators of tumor immunity, we constructed an epigenetic-focused sgRNA library, and performed an in vivo CRISPR screen in a KrasG12D/P53-/- (KP) lung ADC model. Our data showed that loss of the histone chaperone Asf1a in tumor cells sensitizes tumors to anti-PD-1 treatment. Mechanistic studies revealed that tumor cell-intrinsic Asf1a deficiency induced immunogenic macrophage differentiation in the tumor microenvironment by upregulating GM-CSF expression and potentiated T cell activation in combination with anti-PD-1. Our results provide rationale for a novel combination therapy consisting of ASF1A inhibition and anti-PD-1 immunotherapy.

OBJECTIVES/OBJECTIVE:To evaluate the causes of 30-day readmissions following orthopedic trauma surgery and classify them based on their relation to the index admission. DESIGN/METHODS:Retrospective chart review. SETTING/METHODS:One large, academic medical center. PARTICIPANTS/METHODS:Patients admitted to a large, academic medical center for a traumatic fracture injury over a nine-year period. INTERVENTION/METHODS:Assignment of readmission classification. MAIN OUTCOME MEASUREMENTS/METHODS:Readmissions within 30 days of discharge were identified and classified into: orthopedic complications; medical complications; and non-complications. A chi-square test was performed to assess any difference in the proportion of readmissions between the hospital-reported readmission rate and the orthopedic complication readmission rate. RESULTS:1,955 patients who were admitted between 2011-2018 for an acute orthopedic trauma fracture injury were identified. Eighty-nine patients were readmitted within 30 days of discharge with an overall readmission rate of 4.55%. Within the 30-day readmission cohort, 30 (33.7%) were the direct result of orthopedic treatment complications, 36 (40.4%) were unrelated medical conditions, and 23 (25.8%) were non-complications. Thus, the readmission rate directly due to orthopedic treatment complications was 1.53%. A chi-square test of homogeneity revealed a statistically significant difference between the hospital-reported readmission rate and the orthopedic-treatment complication readmission rate, p < .0005. CONCLUSION/CONCLUSIONS:The use of 30-day readmissions as a measure of hospital quality of care overreports the number of preventable readmissions and penalizes surgeons and hospitals for caring for patients with less optimal health. LEVEL OF EVIDENCE/METHODS:Diagnostic Level III.

Because the incidence of breast cancer increases decades after ionizing radiation exposure, aging has been implicated in the evolution of the tumor microenvironment and tumor progression. Here, we investigated radiation-induced carcinogenesis using a model in which the mammary glands of 10-month-old BALB/c mice were transplanted with Trp53-null mammary tissue three days after exposure to low doses of sparsely ionizing γ-radiation or densely ionizing particle radiation. Mammary transplants in aged irradiated hosts gave rise to significantly more tumors that grew more rapidly than those in sham-irradiated mice, with the most pronounced effects seen in mice irradiated with densely ionizing particle radiation. Tumor transcriptomes identified a characteristic immune signature of these aggressive cancers. Consistent with this, fast-growing tumors exhibited an immunosuppressive tumor microenvironment with few infiltrating lymphocytes, abundant immunosuppressive myeloid cells, and high cyclooxgenase-2 and TGFβ. Only aged irradiated hosts gave rise to tumors lacking cytotoxic CD8+ lymphocytes (defined here as immune desert), which also occurred in younger mice. These data suggested that host irradiation may promote immunosuppression. To test this, young chimera mice were fed chow containing a honeybee-derived compound with anti-inflammatory and immunomodulatory properties, caffeic acid phenethyl ester (CAPE). CAPE prevented the detrimental effects of host irradiation on tumor growth rate, immune signature, and immunosuppression. These data indicated that low-dose radiation, particularly densely ionizing radiation, promoted more aggressive cancers by suppressing antitumor immunity. Dietary intervention with a non-toxic immunomodulatory agent could prevent systemic effects of radiation that fuel carcinogenesis, supporting the potential of this strategy for cancer prevention.