Date of Graduation
Doctor of Philosophy (PhD)
Cancer is second leading cause of death in the United States. Improving cancer care through patient care, research, education and prevention not only saves lives, but reduces health care cost as well. Breast cancer is the most leading cause of cancer incidence and cancer related death in women of the United States. 14-3-3s are a family of conserved proteins ubiquitously expressed in all eukaryotic organisms. They form complexes with hundreds of proteins by binding to specific phospho-serine/threonine containing motifs. In this way they regulate a variety of cellular processes and are involved in many human diseases especially cancer to our interest. Our lab and others recently reported that the 14-3-3z (zeta) isoform is overexpressed in ~45% breast cancers, which predicted poor patient outcome. 14-3-3z overexpression confers chemotherapy resistance. Additionally, 14-3-3z prevents anoikis by suppressing p53 and promotes epithelial mesenchymal transition by activating the TGB-b signaling pathway, which plays important roles during tumor formation and progression. Based on these l hypothesized that 14-3-3z plays an important role in breast cancer.
To systematically study the role of 14-3-3z in breast cancer in vivo, I generated a strong 14-3-3z hypomorphic mutant mouse model by Gene Trap. We found that the homozygous mutant mice are lethal neonatally due to respiratory failure. This lethality could be rescued when outbred to CD-1 or backcrossed to FVB/N mouse strain.
Early mammary gland development was not significantly affected in 14-3-3z homozygous mutant mice. When crossed with MMTV driven Polyoma Middle-T or Neu oncogene transgenic tumor prone mouse, the 14-3-3z mutant mice had longer tumor latency and reduced lung metastasis compared to their wild type counterpart. The tumor samples from the 14-3-3z mutant mice displayed reduced proliferation, increased apoptosis and reduced angiogenesis. Multiple genes were differentially expressed in the 14-3-3z knockout tumors. MiR-126 was an important microRNA mediating both the lethality and tumorigenesis inhibition phenotype.
In addition, 14-3-3z knockout mice are smaller than their litter mates. This growth retardation was accompanied with reduced growth hormone but increased IGF-1 level in the circulation. The knockout mice had a defect in glucose homeostasis. They have lower blood glucose and tolerate glucose better than their wild type counterparts due to reduced glucose uptake. The aberrant glucose homeostasis was accompanied by reduced Hif1-a and Igf1r expression.
The 14-3-3z knockout mice had other phenotypes that need to be further characterized. This mouse strain provided new resource to study 14-3-3z function in vivo and potentially could benefit patients that have aberrant expression of 14-3-3z.
14-3-3zeta, development, cancer