1029

CDKN2A

Detachment of epithelial cells from matrix or attachment to an inappropriate matrix engages an apoptotic response known as anoikis, which prevents metastasis. Cellular sensitivity to anoikis is compromised during the oncogenic epithelial-to-mesenchymal transition (EMT), through unknown mechanisms. We report here a pathway through which EMT confers anoikis resistance. NRAGE (neurotrophin receptor-interacting melanoma antigen) interacted with a component of the E-cadherin complex, ankyrin-G, maintaining NRAGE in the cytoplasm. Oncogenic EMT downregulated ankyrin-G, enhancing the nuclear localization of NRAGE. The oncogenic transcriptional repressor protein TBX2 interacted with NRAGE, repressing the tumor suppressor gene p14ARF. P14ARF sensitized cells to anoikis; conversely, the TBX2/NRAGE complex protected cells against anoikis by downregulating this gene. This represents a novel pathway for the regulation of anoikis by EMT and E-cadherin.

To determine whether p16 (INK4a) deletion ameliorated renal tubulointerstitial injury by inhibiting a senescence-associated secretory phenotype (SASP) in Bmi-1-deficient (Bmi-1 (-/-)) mice, renal phenotypes were compared among 5-week-old Bmi-1 and p16 (INK4a) double-knockout, and Bmi-1 (-/-) and wild-type mice. Fifth-passage renal interstitial fibroblasts (RIFs) from the three groups were analyzed for senescence and proliferation. The effect of Bmi-1 deficiency on epithelial-to-mesenchymal transition (EMT) was examined in Bmi-1-knockdown human renal proximal tubular epithelial (HK2) cells, which were treated with concentrated conditioned medium (CM) from the fifth-passage renal interstitial fibroblasts (RIFs) of above three group mice or with exogenous TGF-beta1. Our results demonstrated that p16 (INK4a) deletion largely rescued renal aging phenotypes caused by Bmi-1 deficiency, including impaired renal structure and function, decreased proliferation, increased apoptosis, senescence and SASP, DNA damage, NF-kappaB and TGF-beta1/Smad signal activation, inflammatory cell infiltration, and tubulointerstitial fibrosis and tubular atrophy. P16 (INK4a) deletion also promoted proliferation, reduced senescence and SASP of RIFs and subsequently inhibited EMT of Bmi-1-knockdown HK2 cells. TGF-beta1 further induced the EMT of Bmi-1-knockdown HK2 cells. Thus, p16 (INK4a) positive senescent cells would be a therapeutic target for preventing renal tubulointerstitial injury.