RESUMEN
Disruption of the CDKN2A (INK4A/ARF) and B (INK4B) genes, which encode three function-independent tumor suppressors, is one of the most common events in human cancer. Because their relative importance in tumor prevention appears to be species- and context-specific, studying their regulation can shed light on mechanisms by which they are bypassed in malignant transformation. We previously unveiled a new pathway in which TGFß selectively induces Arf at mouse Cdkn2a in eye development and cultured fibroblasts. As TGFß signaling is often derailed in cancer development or progression, we investigated its control of CDKN2A/B in human cancer. Computational analyses of sequencing and array data from nearly 11,000 patients with cancer in TCGA showed discordant expression of ARF and INK4A in most cancer subtypes, with gene copy-number loss and promoter methylation involved in only a subset. Using HeLa cells as a model, we found that exogenous TGFß induced ARF mRNA and protein, and ARF knockdown limited TGFß-mediated growth suppression. TGFß-mediated ARF mRNA induction required SMAD2/3, p38MAPK, and SP1, and ARF mRNA was induced without added RNAPII recruitment. Chromatin immunoprecipitation unveiled a remote enhancer element engaged by TGFß by a mechanism that partially depended on p38MAPK. CRISPR-based editing of this enhancer limited induction of ARF and INK4B by TGFß, but not by oncogenic RAS. IMPLICATIONS: Our findings reveal new molecular mechanisms by which CDKN2A/B regulation is coupled to external cues, and those findings represent entry points to further explore pharmacologic strategies to restore their expression in cancer.
Asunto(s)
Inhibidor p15 de las Quinasas Dependientes de la Ciclina/genética , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Elementos de Facilitación Genéticos , Neoplasias/genética , Factor de Crecimiento Transformador beta/farmacología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Inhibidor p15 de las Quinasas Dependientes de la Ciclina/metabolismo , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Técnicas de Silenciamiento del Gen , Células HeLa , Humanos , Modelos Biológicos , Neoplasias/metabolismo , Transducción de Señal/efectos de los fármacos , Regulación hacia ArribaRESUMEN
Multimeric interactions that occur in biology provide impetus for chemists to explore new types of synthetic multivalent ligands that alter cellular functions by mechanisms inaccessible to natural substances. While many different molecules such as peptides, antibody fragments, carbohydrates and organic moieties have been used in developing multimeric ligands, it is worth exploring other important molecular types that have hardly been tested in developing multimeric compounds. Peptoids are one such class of compounds with highly facile synthesis as well as much better biologically amenable qualities. Recently, we identified two HCC4017 lung cancer cell targeting peptoids. Here we explore the possibility of synthesizing multimers of these compounds completely through a solid phase synthesis approach. We have synthesized mini-libraries of homodimers, homotrimers and most importantly, heterodimers of our lung cancer specific compounds. The idea is to develop series of compounds that only differs by the linker portion, which is readily adjustable within the library. The purpose of this is to find the optimal distance between each monomeric unit of the multimer that allows them to perfectly interact with their individual biological targets displayed on the cell surface. Future screens of these minilibraries will identify the multimers with improved binding affinities.