Omer H. Yilmaz, Ph.D. - US grants

Koch Institute Members use vertebrate model organisms as a key tool to study the role of known or putative cancer genes in development and tumorigenicity; investigate the mechanisms of tumor initiation, progression and metastasis; evaluate the role of stroma and immune responses in tumorigenesis; and assess the efficacy of drugs, nanomaterials and devices in therapeutic and diagnostic applications. Thus, it is essential that Center Members are able to correctly diagnose developmental and tumor phenotypes, evaluate the underlying molecular events, and accurately and quantitatively assess drug or vaccine delivery and therapeutic response. The Koch Institute Histology Core is a Shared Resource that provides state-of-the-art histological services to support these studies. This includes assistance and/or training in tissue sectioning, slide preparation and analysis, and access to the consultative services of an internationally recognized Veterinary Pathologist, Dr. Roderick Bronson for diagnosis of tumor and developmental phenotypes. In the current period, the capabilities of this Core have been expanded and enhanced. This includes moving into a larger, custom-designed space in the new Koch Institute building, an increase in the staff and the acquisition of new instrumentation including the addition of automated immunohistochemistry and special staining capabilities. Notably, in the same period, usage of the Histology Core by Center Members increased from 53% to 67%, and included investigators from all four Programs. Thus, this Shared Resource is essential to the success of the Koch Institute mission. In the upcoming period, the Histology Core will continue to offer a wide range of state-of-the-art histological services to support the research programs of Center Members. In spite of the significant expansion of services, and the resulting increased costs of running this Core, the requested CCSG budget for Year 44 is essentially the same as the requested and recommended budget in Year 39.

DESCRIPTION (provided by applicant): The long-term goal of this research is to improve platinum-based cancer therapy. Platinum drugs are administered to nearly half of all cancer patients receiving chemotherapy. Despite the efficacy of these treatments, drug resistance, toxic side effects, and tumor recurrence are critical barriers that need to be addressed for the next generation of platinum chemotherapeutics. Overcoming these obstacles requires improved understanding of factors that stabilize platinum compounds en route to the tumor, the invention of better strategies for selective drug uptake and retention, and the design of constructs that eradicate cancerous tissue. The three specific aims of the proposed research address these objectives. The first aim is to deploy methods for directing platinum agents to cancer cells by targeting their unique biology. Tactics for achieving this goal include programmed delivery through cancer-specific receptors on the cell surface and the synthesis and evaluation of dual-threat constructs. The latter capitalize on the power of Pt-DNA adducts to arrest transcription and trigger apoptosis while simultaneously disabling factors that undermine efficacy, such as cancer stem cells in the tumor microenvironment. The approaches include linking cancer cell-targeting units or apoptosis-enhancing factors to a platinum(II) drug, or to a platinum(IV) prodrug that will release such a component upon platinum reduction in the cancer cell, as well as packaging the platinum and auxiliary modules in biodegradable nanoparticles. The second aim of this proposal is to understand and improve phenanthriplatin, a recently discovered, uniquely potent cationic platinum complex derived from cisplatin by replacing one of its chloride ligands with phenanthridine. Phenanthriplatin is highly differentiated in the spectrum of cancer cells that it targets compared to any other platinum drug, indicating its potential to circumvent mechanisms that limit conventional platinum chemotherapy. The approaches include investigating the DNA interactions of phenanthriplatin and their effects on cellular function, experiments to probe and stimulate its mechanisms of inducing cell death, and chemically modifying it to install dual-threat features similar to those planned for the cisplatin drug family ultimately to establish the utility of phenanthriplatin in vivo. The final aim is to deliver a high bolus of platinum to cancer cells to improve the therapeutic response. This goal will be met by the synthesis of self-assembled supramolecular constructs based on Pt(II) centers that form a spherical cage with hydrophobic cavities that can accommodate an additional payload of Pt(IV) prodrugs. Taken together, research proposed in the three aims will give rise to a greater understanding of conventional and non-traditional platinum anticancer agents, providing information that will guide the generation of novel and more effective chemotherapeutic candidates. The results of these investigations will also be of value to other investigators in the rapidly expanding field of metal-based medicines, and it is expected that the innovative concepts introduced here for understanding and improving platinum anticancer agents can be readily adapted for other therapeutic DNA-binding metal complexes.

PROJECT SUMMARY Fasting regimens can increase lifespan, improve health or both in diverse species including mammals. Fasting also has an emerging role in inhibiting tumor growth, yet little is known about how it impacts tumor initiation or how fasting-imposed metabolism can be therapeutically exploited to treat established tumors. Given that adult stem cells coordinate tissue adaptation and drive tumorigenesis, understanding the mechanism(s) that mediate their response to fasting has important implications for enhancing tissue repair after injury or aging where stem cell function declines, and may provide new therapeutic inroads for cancer. In the mouse intestine, where LGR5+ intestinal stem cells (ISCs) drive the rapid renewal of the intestinal lining, we showed that fasting augments ISC function by inducing a peroxisome proliferator-activated receptor delta (PPARd) driven fatty acid oxidation (FAO) program, which breaks down free fatty acids into acetyl-CoA units. This work raises the critical question of how fasting functions through the FAO pathway to regulate intestinal stemness. We hypothesize that beta-hydroxybutyrate (?OHB), a ketone body and biosynthetic product of FAO generated acetyl- CoA, functions as a signaling metabolite and energetic substrate that mediates the ISC fasting response. In support of this idea, we recently found that the LGR5+ ISCs strongly express enzymes of the ketogenic pathway that produce ?OHB, including its rate-limiting enzyme HMGCS2 (3-hydroxy-3- methylglutaryl-CoA synthetase 2), compared to non-stem cell populations and that fasting strongly elevates HMGCS2 and ?OHB levels in ISCs. HMGCS2 loss in the small intestine reduces ?OHB levels in LGR5+ ISCs and skews their differentiation towards secretory cell fates, which we showed can be rescued by exogenous ?OHB and class I histone deacetylases (HDACs) inhibitor treatment. Mechanistically, ?OHB acts as a signaling metabolite to reinforce the NOTCH program in ISCs by inhibiting HDAC-mediated transcriptional repression. Dynamic control of ?OHB levels in ISCs, therefore, could enable the rapid adaptation of the intestine to diverse physiological states like fasting. Many important questions that form the basis of our aims remain regarding the role ketone bodies as effectors of the fasting response in ISCs such as understanding the in vivo signaling (Aim 1) and energetic (Aim 2) roles of ?OHB in this process. Another critical question is to decipher how the fasting-induced FAO program in ISCs influences tumor initiation and progression (Aim 3). !