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BackgroundThe evolutionary conserved cyclin-dependent kinase phosphatase hCdc14A has been shown to play potential roles in the regulation of mitotic exit and in the centrosome duplication cycle. We have recently shown that hCdc14A also can interact with the tumor suppressor p53 both in vitro and in vivo and specifically dephosphorylates the ser315 site of p53 in vitro. In this study we developed antibodies against hCdc14A to investigate the expression and regulation of hCdc14A in human tissues and cancer cells.ResultsWe show that hCdc14A is differentially expressed in human tissues and in 75 cancer cell lines examined. Treatments with the histone deacetylase inhibitor TSA, the demethylating agent 5-aza-2'-deoxycytodine or the proteasome inhibitor MG132 significantly induced expression of hCdc14A in cell lines expressing low or undetectable levels of hCdc14A. There was a strong bias for low expression of hCdc14A in cancer cell lines harboring wild-type p53, suggesting that high Cdc14A expression is not compatible with wild-type p53 expression. We present evidence for a role for hCdc14A in the dephosphorylation of the ser315 site of p53 in vivo and that hCdc14A forms a complex with Cdk1/cyclin B during interphase but not during mitosis.ConclusionOur results that hCdc14A is differentially expressed in human cancer cells and that hCdc14A can interact with both p53 and the Cdk1/cyclin B complex may implicate that dysregulation of hCdc14A expression may play a role in carcinogenesis.

MDM4 is a promising target for cancer therapy, as it is undetectable in most normal adult tissues but often upregulated in cancer cells to dampen p53 tumor-suppressor function. The mechanisms that underlie MDM4 upregulation in cancer cells are largely unknown. Here, we have shown that this key oncogenic event mainly depends on a specific alternative splicing switch. We determined that while a nonsense-mediated, decay-targeted isoform of MDM4 (MDM4-S) is produced in normal adult tissues as a result of exon 6 skipping, enhanced exon 6 inclusion leads to expression of full-length MDM4 in a large number of human cancers. Although this alternative splicing event is likely regulated by multiple splicing factors, we identified the SRSF3 oncoprotein as a key enhancer of exon 6 inclusion. In multiple human melanoma cell lines and in melanoma patientderived xenograft (PDX) mouse models, antisense oligonucleotide-mediated (ASO-mediated) skipping of exon 6 decreased MDM4 abundance, inhibited melanoma growth, and enhanced sensitivity to MAPK- targeting therapeutics. Additionally, ASO-based MDM4 targeting reduced diffuse large B cell lymphoma PDX growth. As full-length MDM4 is enhanced in multiple human tumors, our data indicate that this strategy is applicable to a wide range of tumor types. We conclude that enhanced MDM4 exon 6 inclusion is a common oncogenic event and has potential as a clinically compatible therapeutic target., Introduction The MDM2-related protein MDM4 contributes to p53 inactivation during embryonic development (1). In contrast to MDM2, however, MDM4 is only expressed at low or undetectable levels in most adult [...]

Regulation of epidermal growth factor receptor (EGFR) signaling requires the concerted action of both positive and negative factors. While the existence of numerous molecules that stimulate EGFR activity has been well documented, direct biological inhibitors appear to be more limited in number and phylogenetic distribution. Kekkon1 (Kek1) represents one such inhibitor. Kek1 was initially identified in Drosophila melanogaster and appears to be absent from vertebrates and the invertebrate Caenorhabditis. To further investigate Kek1's function and evolution, we identified kek1 orthologs within dipterans. In D. melanogaster, kek1 is a transcriptional target of EGFR signaling during oogenesis, where it acts to attenuate receptor activity through an inhibitory feedback loop. The extracellular and transmembrane portion of Kek1 is sufficient for its inhibitory activity in D. melanogaster. Consistent with conservation of its role in EGFR signaling, interspecies comparisons indicate a high degree of identity throughout these regions. During formation of the dorsal-ventral axis Kek1 is expressed in dorsal follicle cells in a pattern that reflects the profile of receptor activation. D. virilis Kek1 (DvKek1) is also expressed dynamically in the dorsal follicle cells, supporting a conserved role in EGFR signaling. Confirming this, biochemical and transgenic assays indicate that DvKek1 is functionally interchangeable with DmKek1. Strikingly, we find that the cytoplasmic domain contains a region with the highest degree of conservation, which we have implicated in EGFR inhibition and dubbed the Kek tail (KT) box.

Abstract Background The evolutionary conserved cyclin-dependent kinase phosphatase hCdc14A has been shown to play potential roles in the regulation of mitotic exit and in the centrosome duplication cycle. We have recently shown that hCdc14A also can interact with the tumor suppressor p53 both in vitro and in vivo and specifically dephosphorylates the ser315 site of p53 in vitro. In this study we developed antibodies against hCdc14A to investigate the expression and regulation of hCdc14A in human tissues and cancer cells. Results We show that hCdc14A is differentially expressed in human tissues and in 75 cancer cell lines examined. Treatments with the histone deacetylase inhibitor TSA, the demethylating agent 5-aza-2'-deoxycytodine or the proteasome inhibitor MG132 significantly induced expression of hCdc14A in cell lines expressing low or undetectable levels of hCdc14A. There was a strong bias for low expression of hCdc14A in cancer cell lines harboring wild-type p53, suggesting that high Cdc14A expression is not compatible with wild-type p53 expression. We present evidence for a role for hCdc14A in the dephosphorylation of the ser315 site of p53 in vivo and that hCdc14A forms a complex with Cdk1/cyclin B during interphase but not during mitosis. Conclusion Our results that hCdc14A is differentially expressed in human cancer cells and that hCdc14A can interact with both p53 and the Cdk1/cyclin B complex may implicate that dysregulation of hCdc14A expression may play a role in carcinogenesis.