Mortality in cancer is most often due to the development of distant metastases for which almost no effective systemic treatments exist. The study of genes relevant for the regulation of metastasis in vivo is therefore of great importance. The functions of p63, a p53 family member, are beginning to be understood in contexts in which p53 function has been well established, including apoptosis and tumor suppression (Su et al., Nature 2010) as well as in other roles such as metastasis (Su et al., Nature 2010), skin development, and stem cell maintenance (Su et al., Cell Stem Cell 2009). The complexity of p63 function is due in part to the existence of multiple isoforms that previously could not be studied independently. Full length TA isoforms of p63 contain a transactivation domain, structurally and functionally resembling p53, whereas the ?N isoforms of p63, while also possessing transactivation activity, antagonize the activities of p53 and the TA isoforms of p63 and p73, the other p53 family member. Interestingly, mutant p53, present in a wide variety of human cancers, has been shown to interact with p63 isoforms and inactivate their function. By generating and studying mice with isoform-specific null alleles of p63, the TAp63-/- and ?Np63-/- mice, we have shown that these genes have distinct roles in suppression of tumorigenesis and metastasis. TAp63-/- mice are highly susceptible to spontaneous metastatic tumors, and TAp63 potently suppresses tumor metastasis by direct coordinate transcriptional regulation of Dicer and several miRNAs (Su et al., Nature 2010). In addition, we have extended these findings to multiple human tumor types including squamous cell carcinoma, lung adenocarcinoma, and breast adenocarcinoma, indicating this function of TAp63 is widely important. We have also shown that ?Np63 can suppress invasion and transcriptionally regulates DGCR8, another critically important enzyme necessary for miRNA processing. We hypothesize that TAp63 and ?Np63 regulate distinct miRNAs in different cellular compartments to suppress tumorigenesis and metastasis and to engage the DNA damage response. We will address our hypothesis by proposing the following specific aims:
Specific Aim 1 : To understand the mechanistic regulation of miRNA and LincRNA targets by p63 isoforms in the cell of origin of carcinomas (epidermal cells).
Specific Aim 2 : To understand the mechanistic regulation of miRNAs and LincRNAs by p63 isoforms in stem cells of skin cancer and metastasis.
Specific Aim 3 : To understand the roles of miRNAs and LincRNAs regulated by p63 isoforms in the DNA damage response and p53 compensation.

Public Health Relevance

The study of genes relevant for the regulation of metastasis in vivo is of great importance given the high mortality of metastatic cancer, and p63, a p53 family member, plays critical roles to suppress metastasis through coordinate transcriptional regulation of Dicer and microRNAs (miRNAs). The goals of this grant proposal are to identify the miRNA and long non-coding RNA (LincRNA) targets that are regulated by p63 and its isoforms in the suppression of metastasis and the DNA damage response. We will use p63 isoform specific knock out mouse models of metastatic squamous cell carcinoma generated in my laboratory and human patient samples to address this goal.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Cancer Molecular Pathobiology Study Section (CAMP)
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Mietz, Judy
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University of Texas MD Anderson Cancer Center
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United States
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Venkatanarayan, Avinashnarayan; Raulji, Payal; Norton, William et al. (2015) IAPP-driven metabolic reprogramming induces regression of p53-deficient tumours in vivo. Nature 517:626-30
Chakravarti, Deepavali; Su, Xiaohua; Cho, Min Soon et al. (2014) Induced multipotency in adult keratinocytes through down-regulation of ?Np63 or DGCR8. Proc Natl Acad Sci U S A 111:E572-81
Tan, E H; Morton, J P; Timpson, P et al. (2014) Functions of TAp63 and p53 in restraining the development of metastatic cancer. Oncogene 33:3325-33
Eno, Colins O; Zhao, Guoping; Venkatanarayan, Avinashnarayan et al. (2013) Noxa couples lysosomal membrane permeabilization and apoptosis during oxidative stress. Free Radic Biol Med 65:26-37
Su, Xiaohua; Chakravarti, Deepavali; Flores, Elsa R (2013) p63 steps into the limelight: crucial roles in the suppression of tumorigenesis and metastasis. Nat Rev Cancer 13:136-43