Histone Deacetylase Inhibitors for Selective Anti-Cancer Therapeutics

Activating mutations of ras genes are frequently found in human cancers. Since Ras proteins and their functions play an important role in tumorigenesis, it is important to develop targeted anticancer therapeutics against Ras-related human cancers. We observed that in addition to tumorigenic ability, oncogenic H-Ras possesses a novel proapoptotic ability to facilitate the induction of apoptosis by histone deacetylase inhibitors (HDACIs), such as FR901228 and trichostatin A (TSA). HDACIs make up a new class of structurally diverse anticancer agents and have been shown to exhibit antimetastatic and antiangiogenic activities toward malignantly transformed cells. We detected that expression of oncogenic H-Ras potentiated intracellular reactive oxygen species (ROS) in human and mouse cells to enhance HDACI-induced ROS, thereby contributing to the induction of selective apoptosis and caspase activation. The first part (Part I) of this dissertation focuses on the understanding of Ras proteins, their role in normal and transformed cell physiology, and current treatment options against Ras-related human cancers, as well as the role of HDACIs and ROS in anticancer therapeutics. The next three parts (Part II-IV) focus on revealing the mechanisms for the novel pro-apoptotic ability of oncogenic H-Ras that allow HDACIs to induce selective apoptosis of the oncogenic H-Ras expressing cells. Results in Part II & III verify the pro-apoptotic activity of oncogenic H-Ras in the increased susceptibility of human cancer cells to HDACIs. The caspase pathways, the B-Raf and extracellular signal regulated kinase pathway, p21Cip1 and p27Kip1, and core histone contents are regulated differently by FR901228 in oncogenic H-Ras–expressed cells than their counterparts in parental cells, contributing to the increased susceptibility to the induction of selective apoptosis. Results in Part IV describe the role of reactive oxygen species in the pro-apoptotic ability ofoncogenic H-Ras to enhance the cell susceptibility to HDACIs. Intracellular ROS was cooperatively up-regulated by oncogenc H-Ras and HDACI treatment to induce selective apoptosis of oncogenic H-Ras-expressing cells. The last section (Part V) summarizes the findings with their importance and discusses future directions

Impact of Microcystin-LR on Liver Function Varies by Dose and Sex in Mice

Microcystin (MC) exposure is an increasing concern because more geographical locations are covered with cyanobacterial blooms as eutrophication and bloom-favoring environmental factors become more prevalent worldwide. Acute MC exposure has been linked to gastrointestinal distress, liver toxicity, and death in extreme circumstances. The goal of this study was to provide an accurate and comprehensive description of MC-LRs impacts on liver pathology, clinical chemistry, and gap junction intercellular communication (GJIC) in CD-1 male and female mice. Mice were exposed to 0, 3000, and 5000/4000 µg/kg/day MC-LR, daily for 7 days, and were necropsied on Day 8. Blood samples for clinical chemistry analysis were processed to serum, while liver sections were fixed for histopathology or evaluated for GJIC using fluorescent cut-load dye. Results show a dose-dependent relationship with MC-LR exposure and hepatocellular hypertrophy, degradation, and necrosis. Clinical chemistry parameters alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, and cholesterol increased significantly in MC-LR exposed mice. Clinical chemistry parameter analysis showed significantly increased susceptibility to MC-LR in females compared to males. Changes in GJIC were not noted, but localization of hepatotoxicity near the central veins and midlobular areas was seen. Future toxicity studies involving MCs should consider response differences across sexes, differing MC congeners, and combinatorial exposures involving other cyanotoxins

Toxicological Assessments of a Pandemic COVID-19 Vaccine—Demonstrating the Suitability of a Platform Approach for mRNA Vaccines

The emergence of SARS-CoV-2 at the end of 2019 required the swift development of a vaccine to address the pandemic. Nonclinical GLP-compliant studies in Wistar Han rats were initiated to assess the local tolerance, systemic toxicity, and immune response to four mRNA vaccine candidates encoding immunogens derived from the spike (S) glycoprotein of SARS-CoV-2, encapsulated in lipid nanoparticles (LNPs). Vaccine candidates were administered intramuscularly once weekly for three doses at 30 and/or 100 µg followed by a 3-week recovery period. Clinical pathology findings included higher white blood cell counts and acute phase reactant concentrations, lower platelet and reticulocyte counts, and lower RBC parameters. Microscopically, there was increased cellularity (lymphocytes) in the lymph nodes and spleen, increased hematopoiesis in the bone marrow and spleen, acute inflammation and edema at the injection site, and minimal hepatocellular vacuolation. These findings were generally attributed to the anticipated immune and inflammatory responses to the vaccines, except for hepatocyte vacuolation, which was interpreted to reflect hepatocyte LNP lipid uptake, was similar between candidates and resolved or partially recovered at the end of the recovery phase. These studies demonstrated safety and tolerability in rats, supporting SARS-CoV-2 mRNA-LNP vaccine clinical development