Anti-CRK monoclonal antibody, clone 4H22D2

Phorbol 12-myristate 13-acetate (PMA) stimulates the differentiation of promyelocytic leukemia HL-60 cells by inducing adhesion followed by cell aggregation and, importantly, apoptosis. p130Cas (Crk-associated substrate) is an adapter molecule that controls cell growth, attachment and apoptotic programs. Notably, elevated p130Cas activity is associated with leukemias and lymphomas. Since p130Cas regulates cell adhesion, we tested the hypothesis that it participates in the differentiation of hematopoietic cells. Here we show that PMA mediates the late induction of p130Cas expression in HL-60 cells, which coincided with cell aggregation and the onset of apoptosis. Ectopic p130Cas expression led to increased cell adhesion and earlier cell aggregation potentially contributing to the observed increased cell viability in these transductants. p130Cas expression concurred with the induction of its own regulator the transcription factor EGR1, its coregulator NAB2, and apoptosis. NF-kappa B inhibition in PMA-treated HL-60 cells promoted the loss of cell aggregation and cell death. We further showed a reduction of p130Cas, EGR1, and NAB2 levels in response to NF-kappa B inhibition during PMA treatment. Hence, p130Cas acts as survival factor by limiting PMA-mediated cell cluster disruption and resulting cell death in HL-60 cells. (c) 2013 Elsevier Ltd. All rights reserved.

The long non-coding RNA (lncRNA) PCAT-1 resides in the chromosome 8q24 cancer-risk locus and acts as a vital oncogene during tumorigenesis and progression. However, how PCAT-1 is post-transcriptionally regulated, for example, by small ncRNAs, such as microRNAs (miRNAs) is largely unknown. Here, we report how miRNAs regulate PCAT-1 expression and also investigate the biological significance of this regulation in hepatocellular carcinoma (HCC). We found that miR-215, a P53-inducible miRNA, is a key regulator of PCAT-1 expression in HCC and identified an interaction between miR-215 and PCAT-1 in dual luciferase reporter gene assays. We also found that post-transcriptional silencing of PCAT-1 by miR-215 or PCAT-1 siRNAs significantly inhibited proliferation of HCC cells and, conversely, that inhibition of endogenous miR-215 up-regulated PCAT-1 expression and promoted cell viability. The tumor-suppressing role of miR-215 was further confirmed in an in vivo mouse HCC xenograft model. Of note, gene profiling assays suggested that the kinase CRK-like proto-oncogene, adaptor protein (CRKL), is a potential downstream target of the miR-215-PCAT-1 axis in HCC, and we demonstrated that CRKL silencing significantly suppresses cell proliferation. Taken together and considering the essential role of CRKL in cancer cells, we propose that the TP53-miR-215-PCAT-1-CRKL axis might represent an important regulatory pathway in HCC. In summary, our results highlight the involvement of several ncRNAs in HCC and thus provide critical insights into the molecular pathways operating in this malignancy.