p63(TP63) elicits strong trans-activation of the MFG-E8/lactadherin/BA46 gene through interactions between the TA and ΔN isoforms

Abstract

We report here that human MFGE8 encoding milk fat globule-EGF factor 8 protein (MFG-E8), also termed 46 kDa breast epithelial antigen and lactadherin, is transcriptionally activated by p63, or TP63, a p53 (TP53) family protein frequently overexpressed in head-and-neck squamous cell carcinomas, mammary carcinomas and so on. Despite that human MFG-E8 was originally identified as a breast cancer marker, and has recently been reported to provide peptides for cancer immunotherapy, its transcriptional control remains an open question. Observations in immunohistochemical analyses, a tetracycline-induced p63 expression system and keratinocyte cultures suggested a physiological link between p63 and MFGE8. By reporter assays with immediately upstream regions of MFGE8, we determined that the trans-activator (TA) isoforms of p63 activate MFGE8 transcription though a p53/p63 motif at À370, which was confirmed by a chromatin immunoprecipitation experiment. Upon siRNAmediated p63 silencing in a squamous cell carinoma line, MFG-E8 production decreased to diminish Saos-2 cell adhesion. Interestingly, the DN-p63 isoform lacking the TA domain enhanced the MFGE8-activating function of TA-p63, if DN-p63 was dominant over TA-p63 as typically observed in undifferentiated keratinocytes and squamous cell carcinomas, implying a self-regulatory mechanism of p63 by the TA:DN association. MFG-E8 may provide a novel pathway of epithelial-nonepithelial cell interactions inducible by p63, probably in pathological processes.

NF-Y loss triggers p53 stabilization and apoptosis in HPV18-positive cells by affecting E6 transcription

“…The level of p63 mRNA, already low in Hela control cells, was further reduced following NF-YA loss. At the protein level, we observed a decrease in ΔNp63, the only isoform we detected by Western blot in control cells (Supplementary Figure S5) [43, 44]. This result is consistent with the established role of NF-Y as transcriptional activator of the ΔNp63 promoter [45].…”

Milk Fat Globule EGF-8 Promotes Melanoma Progression through Coordinated Akt and Twist Signaling in the Tumor Microenvironment

“…Autocrine MFG-E8 production by melanoma cells thereby constitutes an alterative scheme that might be more resistant to varying local conditions. Whereas the specific pathways that regulate MFG-E8 expression in cancer cells remain to be elucidated, p63 may be involved in some cases (43).…”

MFG-E8: Origin, Structure, Expression, Functions and Regulation

“…However, molecular mechanisms involved in the MFG-E8 up-regulation in cancer remain largely unknown. In an in vitro study using keratinocyte and a squamous cell carcinoma line [ 56 ], reporter gene assays using Mfge8 gene promoter regions and chromatin immunoprecipitation experiments showed that the transactivator (TA) isoforms of p63 activated Mfge8 transcription through a p53/p63 [ 57 ] motif at −370. Moreover, p63 siRNA treatment of the squamous carcinoma cells suppressed production of MFG-E8 protein, leading to suppression of the cell adhesion.…”