RESUMO
Cancer-associated fibroblasts (CAFs) expressing podoplanin (PDPN) are a favorable prognosticator in surgically resected small cell lung cancer (SCLC). Here we explore whether CAFs expressing PDPN influence proliferation of SCLC cells. Compared with control group (SCLC cells co-cultured with CAFs-Ctrl), numbers of SCLC cells co-cultured with CAFs overexpressing PDPN were decreased. Suppression of PDPN expression by shRNA in CAFs resulted in increased numbers of SCLC cells. In surgically resected human SCLC specimens, the frequency of Geminin-positive cancer cells was significantly higher in the cases with PDPN-positive CAFs than in the cases with PDPN-negative CAFs. Thus CAFs expressing PDPN inhibit growth of SCLC cells, suggesting that CAFs expressing PDPN represent a tumor inhibitory stromal cell component in SCLC.
Assuntos
Carcinoma de Células Pequenas/patologia , Fibroblastos/fisiologia , Neoplasias Pulmonares/patologia , Glicoproteínas de Membrana/biossíntese , Proteínas de Neoplasias/biossíntese , Células Estromais/fisiologia , Microambiente Tumoral/fisiologia , Adenocarcinoma/patologia , Idoso , Animais , Carcinoma Pulmonar de Células não Pequenas/patologia , Linhagem Celular Tumoral , Técnicas de Cocultura , Feminino , Geminina/biossíntese , Geminina/genética , Regulação Neoplásica da Expressão Gênica , Sobrevivência de Enxerto , Xenoenxertos , Humanos , Masculino , Glicoproteínas de Membrana/genética , Camundongos , Camundongos SCID , Pessoa de Meia-Idade , Proteínas de Neoplasias/genética , Interferência de RNA , RNA Interferente Pequeno/genética , Transfecção , Carga TumoralRESUMO
Geminin performs a central function in regulating cellular proliferation and differentiation in development and also in stem cells. Of interest, down-regulation of Geminin induces gene transcription regulated by E2F, indicating that Geminin is involved in regulation of E2F-mediated transcriptional activity. Because transcription of the Geminin gene is reportedly regulated via an E2F-responsive region (E2F-R) located in the first intron, we first used a reporter vector to examine the effect of Geminin on E2F-mediated transcriptional regulation. We found that Geminin transfection suppressed E2F1- and E2F2-mediated transcriptional activation and also mildly suppressed such activity in synergy with E2F5, 6, and 7, suggesting that Geminin constitutes a negative-feedback loop for the Geminin promoter. Of interest, Geminin also suppressed nuclease accessibility, acetylation of histone H3, and trimethylation of histone H3 at lysine 4, which were induced by E2F1 overexpression, and enhanced tri-methylation of histone H3 at lysine 27 and monoubiquitination of histone H2A at lysine 119 in E2F-R. However, Geminin5EQ, which does not interact with Brahma or Brg1, did not suppress accessibility to nuclease digestion or transcription but had an overall dominant-negative effect. These findings suggest that E2F-mediated activation of Geminin transcription is negatively regulated by Geminin through the inhibition of chromatin remodeling.
