Elucidating the temporal dynamics of NF-κB activation by TNF-α in melanoma

Abstract

Melanoma is a heterogeneous disease resulting from dysregulation of molecular pathways, leading to poorly controlled tumor growth and metastasis if the cancer is not surgically excised in time. NF- κB is a critical transcription factor which underlies several key pathways of cellular growth, though its contribution in melanoma is not well elucidated. TNF-α is a cytokine which activates NF-κB by targeting the IκB inhibitor to the proteasome for degradation. Recent work has suggested that the melanoma stem-like state is directly dependent on TNF-α activity, further stressing the importance of this pathway in melanoma. We have found that TNF-α activation of NF-κB causes transcription of several genes, including A20, NFKBIA, and NFKBIE, which is regulated in a temporal fashion and is concentration dependent. Furthermore, this activation can be modulated through pharmacologic agents including bortezomib, which blocks proteasome degradation of IκB, thereby delaying or preventing TNF-α activity. We have also generated a fluorescent lentiviral-based reporter system for directly observing NF-κB protein expression and localization (through a p65-fluorescent protein fusion) in the cytoplasm and nucleus in order to better elucidate the dynamics of NF-κB activity in melanoma and are concurrently working to model these dynamics. The NF-κB pathway represents an important aspect in melanoma pathogenesis and our work serves to elucidate the mechanism of this activation which may be useful in developing novel strategies to block growth.