RESUMEN
Prostate apoptosis response-4 (Par-4), a proapoptotic tumor suppressor protein, is downregulated in many cancers including renal cell carcinoma, glioblastoma, endometrial, and breast cancer. Par-4 induces apoptosis selectively in various types of cancer cells but not normal cells. We found that chronic lymphocytic leukemia (CLL) cells from human patients and from Eµ-Tcl1 mice constitutively express Par-4 in greater amounts than normal B-1 or B-2 cells. Interestingly, knockdown of Par-4 in human CLL-derived Mec-1 cells results in a robust increase in p21/WAF1 expression and decreased growth due to delayed G1-to-S cell-cycle transition. Lack of Par-4 also increased the expression of p21 and delayed CLL growth in Eµ-Tcl1 mice. Par-4 expression in CLL cells required constitutively active B-cell receptor (BCR) signaling, as inhibition of BCR signaling with US Food and Drug Administration (FDA)-approved drugs caused a decrease in Par-4 messenger RNA and protein, and an increase in apoptosis. In particular, activities of Lyn, a Src family kinase, spleen tyrosine kinase, and Bruton tyrosine kinase are required for Par-4 expression in CLL cells, suggesting a novel regulation of Par-4 through BCR signaling. Together, these results suggest that Par-4 may play a novel progrowth rather than proapoptotic role in CLL and could be targeted to enhance the therapeutic effects of BCR-signaling inhibitors.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/metabolismo , Regulación Leucémica de la Expresión Génica , Leucemia Linfocítica Crónica de Células B/metabolismo , Animales , Proteínas Reguladoras de la Apoptosis/genética , Ciclo Celular , Línea Celular Tumoral , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Eliminación de Gen , Humanos , Leucemia Linfocítica Crónica de Células B/genética , Leucemia Linfocítica Crónica de Células B/patología , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Receptores de Antígenos de Linfocitos B/metabolismo , Transducción de Señal , Regulación hacia ArribaRESUMEN
The chronic lymphocytic leukemia (CLL) microenvironment has been receiving an increasing amount of attention, but there is currently limited data surrounding how the microenvironment affects initial development of CLL. We determined that the spleen is the initial site of CLL growth through monitoring of transgenic Eµ-TCL1 mice that develop CLL. Subsequently, we isolated stromal cells from the spleens of Eµ-TCL1 mice (EMST cells) that induce CLL cell division in vitro. Both cell-cell contact and soluble factors were involved in EMST-induced CLL cell division. These stromal cells are present in significantly larger numbers in the spleen than other lymphoid organs. We also noted that splenectomy delayed CLL development in Eµ-TCL1 mice and completely prevented CLL development in adoptive transfer mice. Our findings will allow future studies surrounding the CLL microenvironment to focus upon the splenic stromal cells.
Asunto(s)
Leucemia Linfocítica Crónica de Células B , Animales , Leucemia Linfocítica Crónica de Células B/genética , Ratones , Ratones Transgénicos , Proteínas Proto-Oncogénicas , Bazo , Células del Estroma , Microambiente TumoralRESUMEN
Our previous work identified a 13-gene miRNA signature predictive of response to the epidermal growth factor receptor (EGFR) inhibitor, erlotinib, in Non-Small Cell Lung Cancer cell lines. Bioinformatic analysis of the signature showed a functional convergence on TGFß canonical signalling. We hypothesized that TGFß signalling controls expression of the miRNA genes comprising an erlotinib response signature in NSCLC. Western analysis revealed that TGFß signalling via Smad2/3/4 occurred differently between erlotinib-resistant A549 and erlotinib- sensitive PC9 cells. We showed that TGFß induced an interaction between Smad4 and putative Smad Binding Elements in PC9. However, qRT-PCR analysis showed that endogenous miR-140/141/200c expression changes resulted from time in treatments, not the treatments themselves. Moreover, flow cytometry indicated that cells exited the cell cycle in the same manner. Taken together these data indicated that the miRNA comprising the signature are likely regulated by the cell cycle rather than by TGFß. Importantly, this work revealed that TGFß did not induce EMT in PC9 cells, but rather TGFß-inhibition induced an EMT-intermediate. These data also show that growth/proliferation signals by constitutively-activated EGFR may rely on TGFß and a possible relationship between TGFß and EGFR signalling may prevent EMT progression in this context rather than promote it.