Abstract:
Dysregulated expression of Fas-associated death domain (FADD) is associated with the
impediment of various cellular pathways, including apoptosis and inflammation. The adequate
cytosolic expression of FADD is critical to the regulation of cancer cell proliferation. Importantly,
cancer cells devise mechanisms to suppress FADD expression and, in turn, escape from apoptosis
signaling. Formulating strategies, for direct delivery of FADD proteins into cancer cells in a controlled
manner, may represent a promising therapeutic approach in cancer therapy. We chemically conjugated
purified FADD protein with cell permeable TAT (transactivator of transcription) peptide, to deliver in
cancer cells. TAT-conjugated FADD protein internalized through the caveolar pathway of endocytosis
and retained in the cytosol to augment cell death. Inside cancer cells, TAT-FADD rapidly constituted
DISC (death inducing signaling complex) assembly, which in turn, instigate apoptosis signaling.
The apoptotic competency of TAT-FADD showed comparable outcomes with the conventional
apoptosis inducers. Notably, TAT-FADD mitigates constitutive NF- B activation and associated
downstream anti-apoptotic genes Bcl2, cFLIPL, RIP1, and cIAP2, independent of pro-cancerous
TNF- priming. In cancer cells, TAT-FADD suppresses the canonical NLRP3 inflammasome priming
and restricts the processing and secretion of proinflammatory IL-1 . Our results demonstrate that
TAT-mediated intracellular delivery of FADD protein can potentially recite apoptosis signaling
with simultaneous regulation of anti-apoptotic and proinflammatory NF- B signaling activation in
cancer cells
