The p53 family of transcription factors includes p63, which is a master regulator of gene expression in epithelial cells. Determining whether p63 is tumor-suppressive or tumorigenic is complicated by Show more
The p53 family of transcription factors includes p63, which is a master regulator of gene expression in epithelial cells. Determining whether p63 is tumor-suppressive or tumorigenic is complicated by isoform-specific and cellular context-dependent protein associations, as well as antagonism from mutant p53. ΔNp63 is an amino-terminal-truncated isoform, that is, the predominant isoform expressed in cancer cells of epithelial origin. In HaCaT keratinocytes, which have mutant p53 and ΔNp63, we found that mutant p53 antagonized ΔNp63 transcriptional activity but that activation of Ras or transforming growth factor-β (TGF-β) signaling pathways reduced the abundance of mutant p53 and strengthened target gene binding and activity of ΔNp63. Among the products of ΔNp63-induced genes was dual-specificity phosphatase 6 (DUSP6), which promoted the degradation of mutant p53, likely by dephosphorylating p53. Knocking down all forms of p63 or DUSP6 and DUSP7 (DUSP6/7) inhibited the basal or TGF-β-induced or epidermal growth factor (which activates Ras)-induced migration and invasion in cultures of p53-mutant breast cancer and squamous skin cancer cells. Alternatively, overexpressing ΔNp63 in the breast cancer cells increased their capacity to colonize various tissues upon intracardiac injection in mice, and this was inhibited by knocking down DUSP6/7 in these ΔNp63-overexpressing cells. High abundance of ΔNp63 in various tumors correlated with poor prognosis in patients, and this correlation was stronger in patients whose tumors also had a mutation in the gene encoding p53. Thus, oncogenic Ras and TGF-β signaling stimulate cancer progression through activation of the ΔNp63 transcriptional program. Show less
We here report the first case of discordant Pena-Shokeir phenotype observed in monoamniotic twins. A 34-year-old woman, pregnant with twins, was referred at 10 weeks' gestation because one of the twin Show more
We here report the first case of discordant Pena-Shokeir phenotype observed in monoamniotic twins. A 34-year-old woman, pregnant with twins, was referred at 10 weeks' gestation because one of the twins had increased nuchal translucency. Serial ultrasonographic examinations suggested that twin A may have had several other abnormalities, including pleural effusion at 21 weeks' gestation, decreased movement and contracted limbs at 24 weeks, and fetal growth restriction at 26 weeks. No abnormalities were observed in twin B. At 34 weeks of gestation, the twins were delivered by cesarean section. There were cord entanglements, and although the resuscitation of twin A was attempted, it proved difficult due to lockjaw. Twin A died during the second hour of life, and autopsy findings were consistent with the diagnosis of Pena-Shokeir phenotype. We suggest that cord entanglement during early gestation is a possible cause for the occurrence of Pena-Shokeir phenotype through an anoxic-ischemic mechanism. Show less