P63-expressing Cells Research Articles

Relationship of p63 and CD44 expressions with age and body sites.

Objective To clarify the relationship of p63 and CD44 expressions with age and ultraviolet irradiation in the process of skin aging.Methods Full-thickness skin samples were obtained from the normal skin at different sites,including 44 sun-exposed sites(face,neck,dorsal aspect of the forearm),46 sun-protected sites(abdomen,thigh),and 31 semi-exposed sites(back,flexor aspect of the forearm,upper arm,leg),of 121 volunteers(63 males and 58 females).Of all the volunteers,55 were 10 t0 30 vears of age (young),41 were 31 to 50 years of age(adult),and 25 were 51 to 79 years of age(old).Immunohistochemisty using antibodies to p63 and CD44 was applied to detect the expression of p63 and CD44 in these specimens.Imaging analysis software was utilized to calculate the percentage of p63-expressing cells in basal layer as well as the expression level of p63 and CD44.Results In stratum basale,the percentage of p63-expressing cells decreased with age(r=-0.218,P＜0.05),but showed no significant difference among sun-exposed skin,semi-exposed skin and sun-protected skin(P＞0.05).The correlation between the expression intensity of epidermal p63 and age was negative in sun-exposed sites(r=-0.389,P=0.010),positive in sun-protected sites(r=0.341,P＜0.05).but non-significant in semi-exposed sites(P＞0.05).With regard to the expression of epidermal p63,no significant difference was observed among sun-exposed sites,sun-protected sites and semi-exposed sites in volunteers aged from 10 to 30 years.while in those aged from 31 to 50 years and from 51 to 79 years.sun-protected sites was significantly higher than semi-exposed sites followed by sun-exposed sites(all P＜0.05).There was a weak correlation between the expression intensity of epidermal CD44 and age(r=-0.083,P＜0.05),but no significant difierence was noted among the three kinds of sites(P＞0.05).Conclusions In stratum basale,the percentage of p63.expressing cells and the expression intensity Of CD44 negatively correlate with age,but have no correlation with ultraviolet irradiation.In individuals aged from 31 to 50 years and from 51 t0 79 vears.the expression of epidermal p63 decreases with the accumulation of sun-exposure. Key words: Skin aging; Epidermis; Genes,p63; Antigens,CD44

Self-Renewal and Multilineage Differentiation In Vitro from Murine Prostate Stem Cells

Murine prostate stem cells express integrin alpha 6, which modulates survival, proliferation, and differentiation signaling through its interaction with the extracellular protein laminin. When plated in vitro in laminin containing Matrigel medium, 1 of 500-1,000 murine prostate cells can grow and form clonogenic spheroid structures that we term prostate spheres. Prostate spheres can be serially passaged individually or in bulk to generate daughter spheres with similar composition, demonstrating that sphere-forming cells are capable of self-renewal. Spheres spontaneously undergo lineage specification for basal and transit-amplifying cell types. P63-expressing cells localized to the outer layers of prostate spheres possess higher self-renewal capacity, whereas cells toward the center display a more differentiated transit-amplifying phenotype, as demonstrated by the expression of the prostate stem cell antigen. When dihydrotestosterone is added to the medium, the androgen receptor is stabilized, is imported to the nucleus, and drives differentiation to a luminal cell-like phenotype. A fraction of sphere cells returned to an in vivo environment can undergo differentiation and morphogenesis to form prostate tubular structures with defined basal and luminal layers accompanied by prostatic secretions. This study demonstrates self-renewal and multilineage differentiation from single adult prostate stem/progenitor cells in a specific in vitro microenvironment.

Tumor-Specific p73 Up-regulation Mediates p63 Dependence in Squamous Cell Carcinoma

p63 is essential for normal epithelial development and is overexpressed in the vast majority of squamous cell carcinomas (SCC). Recent work had shown that DeltaNp63alpha is essential for survival of SCC cells, raising the possibility that the p63 pathway may be an attractive therapeutic target in these tumors. Nevertheless, it is unknown whether a therapeutic window exists for inhibiting p63 in tumor cells versus normal epithelia. Here, we show that SCC cells are uniquely dependent on DeltaNp63alpha for survival, unlike normal p63-expressing epithelial cells, and that dependence is mediated through tumor-specific up-regulation of the related protein p73. In normal primary human keratinocytes, we find that inhibition of endogenous p63 by RNA interference (RNAi) induces p21(CIP1) expression, inhibits cell cycle progression, and ultimately promotes cellular senescence. In contrast, p63 inhibition in SCC cells induces proapoptotic bcl-2 family members and rapidly triggers apoptosis. Expression of p73 is low in uncultured basal keratinocytes but is markedly up-regulated in both SCC cell lines and primary tumors in vivo. Whereas p21(CIP1) induction following loss of p63 in normal cells is independent of p53 and p73, both proapoptotic gene induction and cell death following p63 RNAi in tumor cells are p73 dependent. Finally, ectopic p73 expression in primary keratinocytes does not affect baseline cell proliferation but is sufficient to trigger cell death following loss of p63. Together, these findings define a specific molecular mechanism of p63 dependence through p73 up-regulation, and they provide a rationale for targeting the p63 pathway as a therapeutic strategy in SCCs.