Title: Developing humanized Nut Carcinoma mouse model for developing NUTM1 targeted therapies.
Project Summary:
NUT carcinoma (NC) is a highly aggressive cancer with no effective treatment (medium survival time ~6 months
from diagnosis). Although considered rare, the decimal prognosis of NC call for the development of better
treatment. Clinically, NC is strongly associated with chromosome translocations that lead to the formation of
fusion genes between a testis-specific gene NUTM1 and various fusion partners, including BRD4 (70% of cases),
and BRD3, NSD3, ZNF532, etc. (the rest 30% of cases). Functionally, knockdown of the BRD4-NUTM1 fusion
gene in human NC cell lines suppresses their proliferation, suggesting a strong dependency on BRD4-NUTM1
by NC. However, because the ectopic expression of BRD4-NUTM1 in non-NC cell lines is unequivocally toxic,
the oncogenic activity of the fusion gene has not been proved previously. Recently, we developed the first
genetically engineered mouse model (GEMM) of NC by recapitulating the Brd4-Nutm1 forming chromosome
translocation in the basal cells of epithelial tissues. The mouse model developed highly aggressive low
differentiation squamous cell carcinoma, similar to human NCs. Our GEMM study provided the first functional
proof of BRD4-NUTM1 as the oncogenic driver of NC. The high dependency of NC on the BRD4-NUTM1 fusion
gene for both cancer initiation and development presented it as an ideal target for therapy. Moreover, the testis-
specific expression profile would make therapeutic strategies targeting NUTM1 highly specific and with a high
therapeutic index. Because NUTM1 is an adaptor protein that is primarily consisted of low-complexity sequences,
there are no apparent target sites for small molecular inhibitors. New therapeutic modules that target its DNA
(e.g., CRISPR-based gene therapy) and mRNA (antisense therapy) sequences, or the ones that target its protein
by synthetic affinity agents (e.g., nanobody-directed Proteolysis Chimera (PROTAC)) would likely be needed.
Due to the limited conservation in genomic DNA (~3%) and peptide sequence (66%), our NC model based
on the mouse genes is not ideal for developing NUTM1-targeting therapeutics. We propose to humanize
the NC GEMM by replacing the mouse Nutm1 gene component with a human NUTM1 coding sequence (Aim 1)
and characterize the NC tumors generated by this humanized model (Aim 2). We expect this well-characterized
humanized NC GEMM to serve as a valuable preclinical model for developing NUTM1 targeting therapies for
NC.
Overall Impact. This project will produce a humanized GEMM for NC. By allowing the preclinical development
of human NUTM1 targeting therapies, our new model can transform the landscape of NC therapy development
and benefit NC patients. More broadly, the knowledge around targeting NUTM1 that the humanized NC model
will foster can provide critical clues for developing NUTM1 targeting therapies for other NUTM1 rearranged
cancers such as childhood leukemia and sarcoma.