Regulation of Neural and Neoplastic Stem Cells by Kruppel-like Transcription Factors

Sponsored by the Maryland Stem Cell Research Fund: 2011-MSCRFII-0073-00.

The effective application of stem cell (SC)-based therapeutics for disorders of the central nervous system require the capacity to tightly regulate neural SC (NSC) self-renewal and differentiation. Advances have been made toward maintaining appropriate NSC multipotency in vitro and in defining conditions that induce neural lineage differentiation. Obstacles such as scalability and cell fate control remain. Uncontrolled self-renewal risks the development of functionally irrelevant mass lesions and even malignant neoplasms. Premature and misdirected differentiation risks repopulating target tissue with or irrelevant cell types. Strategies for differentiating neural stem cells also hold great promise for treating CNS malignancies such as glioblastoma, that contain multipotent neoplastic neural stem-like cells (i.e. cancer SCs, CSCs) believed to play a dominant role in tumor maintenance and recurrence.

Growing evidence shows that normal NSCs and neoplastic CSCs share signaling pathways that regulate their self-renewal and fate determination. Therapeutic approaches based on transcription factor modulation show promise for regulating SC differentiation for regenerative applications and to inhibit CSCs and their capacity to propagate tumors. Emerging evidence implicates Krüppel-like transcription factors (KLFs) as regulators of both neurogenesis and neural oncogenesis. However, the transcriptional networks regulated by KLFs and their importance to neural SC biology remain relatively unknown. Our researchers recently identified a differentiation-induced transcriptional network characterized by KLF9 induction and KLF4 suppression in both non-neoplastic NSCs and GBM-CSCs. They further found that KLF9 inhibits GBM-CSC self-renewal, and induces GBM-CSC differentiation, in part, by directly suppressing Notch1 transcription and Notch signaling.

This proposal is based on the hypothesis that KLF4 and KLF9 play important, distinct, and possibly opposing roles in regulating both NSCs and GBM-CSCs. The experiments proposed in this application will determine the biological and transcriptional mechanisms by which KLF4 and KLF9 regulate NSCs and GBM-CSCs.

• Aim #1: Determine how KLF4 and KLF9 regulate NSC and GBM-CSC self-renewal, differentiation, and potential to survive and grow in vivo.
• Aim #2: Determine the effects of KLF4 and KLF9 on the expression and function of Notch pathway regulators, many of which contain promoter KLF binding sites.
• Aim #3: Identify transcriptional networks directly and indirectly regulated by KLF9 in NSCs and GBM-CSCs.

The results from these experiments will provide vital information regarding self-renewal and fate regulation in non-neoplastic and neoplastic neural stem cells. Our findings will identify translatable mechanisms for controlling stem cell self-renewal and differentiation applicable to regenerative medicine and brain cancer therapy.