Date of Award
12-2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Program
Pharmaceutical Sciences
Track
Medicinal Chemistry
Research Advisor
Wei Li, PhD
Committee
Bernd Meibohm, PhD; Duane D. Miller, PhD; Tiffany N. Seagroves, PhD; Chao-Yie Yang, PhD
Keywords
Human 22Rv1 prostate xenograft model;IAPs inhibitors;Orthotopic ovarian cancer mouse model;P-glycoprotein overexpression;Structure-activity relationship;Tubulin inhibitors
Abstract
The global impact of cancer as a significant public health concern is undeniable. According to the annual report by the American Cancer Society, projections for 2023 estimate 1,958,310 new cancer cases and 609,820 cancer-related deaths in the US. Recent years have seen significant progress in cancer treatment; however, existing therapies face several challenges. Cytotoxic agents-based chemotherapy often has low therapeutic index and encounters drug resistance shortly after initiation, while immunotherapies exhibit low response rates that vary between patients. As a result, there is a pressing need for the development of novel and effective cancer treatment. The work presented here focuses on the identification of new anticancer agents by targeting three important cancer targets: survivin, MDM2, and tubulin. Survivin, a member of the inhibitor of apoptosis proteins (IAPs) family, serves as both an apoptosis suppressor and a pivotal player in cell division. Its significance as a cancer drug target arises from its heightened expression in various human cancers, juxtaposed with its minimal presence in fully differentiated normal tissues. Additionally, survivin is involved in cancer cell resistance against chemotherapy and radiation. Preclinically, downregulation of survivin expression or function has been shown to impede tumor growth, induce apoptosis, and sensitize tumor cells to radiation and chemotherapy in different human tumor models. Chapter 2 describes our discovery of a series of novel survivin inhibitors based on the hydroxyquinoline scaffold from our previously reported lead compound, MX-106. MX-106 selectively downregulated survivin protein levels and induced apoptosis in melanoma A375 and prostate PC3 cancer cells. A new series of MX-106 analogs were designed, synthesized, and tested against a panel of melanoma, breast cancer, and ovarian cancer cell lines. The most promising compound from this study is referred to as compound 12b with an average IC50 value of 1.4 µM. 12b retained its potency against multidrug-resistant melanoma cells (MDA-MB-435/LCC6MDR1) that overexpress P-glycoprotein (P-gp). 12b selectively reduced survivin protein levels, while negligibly affecting other closely related members in the IAP family proteins, leading to pronounced cancer cell apoptosis. In vivo, 12b significantly inhibited melanoma tumor growth in a human A375 melanoma xenograft model. Further evaluation using an aggressive orthotopic ovarian cancer mouse model showcased the high efficacy of 12b in suppressing primary tumor growth in ovaries and hindering tumor metastasis to multiple peritoneal organs. These results strongly suggest that the hydroxyquinoline scaffold, exemplified by 12b exhibits the potential to selectively target survivin and holds promise for further advancement in preclinical development for potential use as effective anticancer agents. An additional promising target for anticancer treatment is the oncogene MDM2. MDM2 is frequently amplified or overexpressed in various human cancers. MDM2 negatively regulates the tumor suppressor p53, inhibiting its function and promoting cancer growth. MDM2 also interacts with other molecules involved in oncogenesis such as the anti-apoptotic protein X-linked inhibitor of apoptosis protein (XIAP). The C-terminal RING domain of MDM2 binds to the internal ribosome entry site (IRES) of the XIAP mRNA and enhances the IRES-dependent translation of XIAP, which results in increased expression of XIAP and resistance to anticancer treatment. On the other hand, binding of XIAP IRES to the RING domain of MDM2 inhibits MDM2 homodimerization and self-ubiquitination, which results in increased MDM2 protein stabilization. This leads to higher levels of MDM2 protein, along with increased XIAP expression, which collectively contributes to cancer progression and drug resistance. Therefore, simultaneous inhibition of MDM2 and XIAP is anticipated to restore the tumor-suppressing role of p53 in wild type p53 (p53WT) tumor cells, similar to existing MDM2 inhibitors that disrupt MDM2-p53 binding, while additionally inducing apoptosis in p53-deficient cancer cells. We have previously identified JW-2-107, a dual MDM2 and XIAP inhibitor. In Chapter 3, we conducted a detailed analysis of the structure-activity relationships (SAR) of the tetrahydroquinoline scaffold of JW-2-107, including screening the new JW-2-107 analogs against a panel of human cancer cell lines including three p53WT cell lines and one p53 mutant cell line. Among the thirty-one newly synthesized JW-2-107 analogs, compound 3e showed the best antiproliferative activity with IC50 values of 0.2, 1, 1.5, and 5.3 μM against EU-1, A375, MDA-MB-231, and 22Rv1 cell lines, respectively. Analog 3e decreased MDM2 and XIAP protein levels while simultaneously promoting p53 expression. Compared to AMG-232, a potent MDM2-p53 inhibitor in clinical trials, 3e showed potency in the p53-mutant MDA-MB-231 cell line while AMG-232 was not active. When tested on a human 22Rv1 prostate cancer xenograft model, compound 3e effectively suppressed tumor growth in vivo. In light of these findings, the tetrahydroquinoline scaffold, represented by compounds like 3e and the earlier lead compound JW-2-107, has the potential to effectively target both MDM2 and XIAP simultaneously and is promising for further preclinical development. Colchicine binding site inhibitors (CBSIs) bind to tubulin heterodimers, disrupting microtubule dynamics, interfering with the mitotic spindle machinery, and inducing mitotic arrest in the G2/M phase, ultimately leading to apoptotic cell death. Unlike the clinically used antitubulins, taxanes and vinca alkaloids, CBSIs are less prone to several known clinical taxanes resistance mechanisms and possess improved aqueous solubility. Our lab previously reported the discovery of VERU-111, a potent and orally bioavailable CBSI with potent preclinical efficacy in multiple tumor models and preliminary clinical efficacy in metastatic castration-resistant prostate cancer patients. Chapter 4 delineates our discovery process of a series of novel CBSIs derived from VERU-111. Those newly synthesized compounds were tested against four different cancer cells, including a multidrug-resistant cancer cell line. The in vitro results showed that several compounds in this series have better anti-proliferative activities than VERU-111. The best two compounds 11b and 11h displayed IC50 values of 0.6 and 1 nM in melanoma and 1.3 and 1.7 nM in prostate cancer cell lines, respectively. Compared with paclitaxel, the new compounds showed advantages in overcoming multiple drug resistance. The mechanism of action for 11b was investigated using X-ray crystallography, tubulin polymerization assay, and cell cycle analysis. In vivo, 11b and 11h significantly inhibited paclitaxel-resistant PC-3 (PC-3/TxR) prostate cancer tumor growth, disrupted tumor angiogenesis, and led to tumor cell apoptosis. Collectively, 11b and 11h represent promising cancer drug candidates for further development.
ORCID
0000-0002-9738-4519
DOI
10.21007/etd.cghs.2023.0642
Recommended Citation
Albadari, Najah Ghazi (0000-0002-9738-4519), "Discovery of Inhibitors of Inhibitors of Apoptosis Proteins and Novel Tubulin Polymerization Inhibitors as Potential Anticancer Agents" (2023). Theses and Dissertations (ETD). Paper 658. http://dx.doi.org/10.21007/etd.cghs.2023.0642.
https://dc.uthsc.edu/dissertations/658