A NOVEL SMALL MOLECULE DNA INTERCALATOR PZ1225 IN CANCER CELL APOPTOSIS AND A HISTONE MODIFIER PAD4 IN MACROPHAGE EXTRACELLULAR TRAP FORMATION

Open Access
Author:
sun, jinquan
Graduate Program:
Molecular, Cellular and Integrative Biosciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
October 05, 2016
Committee Members:
  • Yanming Wang, Dissertation Advisor
  • Zhi-Chun Lai, Committee Chair
  • Douglas Cavener, Committee Member
  • Lu Bai, Committee Member
  • Robert Paulson, Outside Member
Keywords:
  • DNA damage
  • DNA intercalator
  • small molecule
  • MAPK
  • mTOR
  • apoptosis
  • macrophage
  • extracellular traps
  • PAD4
  • citrullination
  • stroke
Abstract:
In the beginning of the 21th century, Douglas Hanahan and Robert Weinberg published couple papers that discussed our understanding of cancer based on studies in the past decades. The authors discussed 8 hallmarks of cancer that define the tumor tissue. These hallmarks include, “1) self-sufficiency in growth signals, 2) insensitivity to antigrowth signals, 3) evading apoptosis (lack of cell attrition mechanisms), 4) limitless replicative potential, 5) sustained angiogenesis, 6) tissue invasion and metastasis”1, 7) the reprogramming of energy metabolism, and 8) the evading immune destruction” 2. They also specified that the genome instability of cancer cells is the underlying mechanism that enables the hallmarks. The traits mentioned above provided a constitutive framework to understand the process of neoplasm. In this Ph.D. dissertation, I will report my exploration on cancer treatment regarding to two of the hallmarks—genomic instability and the invading immune destruction. In one aspect of my Ph.D. study, I have explored the cellular mechanisms of a novel small molecule PZ1225, which intercalate into and distort DNA with a two-indole-ring structure. PZ1225 induced DNA damage results in apoptotic cell death in cancer. In addition, the molecule activates ER stress and UPR response, inhibits autophagy efflux, and activates MAPK signaling. Most importantly, I explored the function of the cell signaling pathways in mediating PZ1225 induced cell death. Using a combination of high through put analyses and cellular biology means, I developed a combination treatment of PZ1225 and a MEK inhibitor U0126. The combination treatment induces apoptosis in cancer cells by more than 2 fold compared to PZ1225 alone and 5 fold compared to U0126 alone. In another aspect, various immune cells grow in the cancer tissue and create a microenvironment benefiting the progression and metastasis of cancer. The extracellular traps formed by neutrophils have been reported to assist cancer metastasis. In my Ph.D. study, I also explored the function of macrophages in forming extracellular traps (ETs). Using the peritoneal macrophages extracted from PAD4 transgenic mice, I observed formation of extracellular traps by macrophages and histone hypercitrullination on the structure. In addition, I elucidated the requirement of the protein arginine deiminase 4 (PAD4) but not PAD2 in hypercitrullination of histones and ET formation. Based on the findings that neutrophil extracellular traps play a role in multiple disease models, I also explored the effects of PAD4 on a mouse stroke model. In the Appendix chapter, I presented the preliminary data that suggest absence of PAD4 protects brain tissue, especially the neuron cells, from ischemia/reperfusion injuries.