Dietary chlorophyllin abrogates TGFβ signaling to modulate the hallmark capabilities of cancer in an animal model of forestomach carcinogenesis

Transforming growth factor (TGF) beta signaling pathway plays a central role in the regulation of a wide range of cellular processes involved in the acquisition of the malignant phenotype. The objective of the present study was to examine the effect of chlorophyllin, a semisynthetic derivative of chlorophyll on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced rat forestomach carcinogenesis based on the modulation of TGF beta signaling and the downstream target genes associated with cell proliferation, apoptosis evasion, angiogenesis, invasion, and metastasis. We determined the effect of dietary chlorophyllin on TGF beta signaling and the downstream events-cell proliferation, apoptosis evasion, angiogenesis, invasion, and metastasis by semiquantitative and quantitative reverse transcription (RT)-PCR, Western blot, and immunohistochemical analyses. We further validated the inhibition of TGF beta signaling by chlorophyllin by performing molecular docking studies. We found that dietary supplementation of chlorophyllin at 4-mg/kg bw inhibits the development of MNNG-induced forestomach carcinomas by downregulating the expression of TGF beta RI, TGF beta RII, and Smad 2 and 4 and upregulating Smad 7, thereby abrogating canonical TGF beta signaling. Docking interactions also confirmed the inhibition of TGF beta signaling by chlorophyllin via inactivating TGF beta RI. Furthermore, attenuation of TGF beta signaling by chlorophyllin also blocked cell proliferation, angiogenesis, invasion, and metastasis, and induced mitochondria-mediated cell death. Dietary chlorophyllin that simultaneously abrogates TGF beta signaling pathway and the key hallmark events of cancer appear to be an ideal candidate for cancer chemoprevention.