Abstract 5494: CX-4945, an inhibitor of protein kinase CK2, potentiates the antitumor activity of platinum chemotherapy in models of ovarian cancer by preventing phosphorylation of XRCC1 and MDC1 and disrupting DNA damage repair

Abstract

Platinum-based chemotherapeutics are commonly used to treat solid tumors but may be restricted in their application by dose limiting toxicity and inherent or acquired resistance. Because efficient DNA damage repair mechanisms contribute to resistance, targeting components of the repair machinery has emerged as a strategy to increase the effectiveness of these and other DNA-damaging anti-cancer drugs. Protein kinase CK2 is a serine/threonine kinase that has emerged as an attractive molecular target due to its overexpression in cancer and regulatory role in key cellular processes including the cell cycle, apoptosis and DNA damage repair. Multiple lines of evidence suggest an increasingly important role for CK2 in the DNA damage response, including the phosphorylation and activation of the mediator/adaptor proteins XRCC1 and MDC1. XRCC1 is an essential component for nucleotide excision repair which is the major repair pathway responsible for removing platinum adducts. MDC1 is the predominant γ-H2AX recognition factor in mammalian cells and is essential for homologous recombination repair. CX-4945 is a first-in-class, selective, oral inhibitor of CK2 currently in Phase 1 clinical trials. We sought to determine if inhibiting CK2 activity with CX-4945 would prevent phosphorylation of XRCC1 and MDC1 and potentiate the activity of platinum-based drugs by preventing DNA damage repair. Treatment of the ovarian cancer cell lines A2780 and SKOV3 with CX-4945 led to decreased phosphorylation of XRCC1 at the CK2 specific phosphorylation sites and reduced total XRCC1 protein levels. Likewise, immunoprecipitation of MDC1 from SKOV3 cells treated with CX-4945 revealed significant reductions in phosphorylation at the CK2 specific sites, while in A2780 cells MDC1 protein levels were decreased. The reduction of MDC1 protein levels was reproduced by CK2 siRNA, confirming that CK2 activity supports MDC1 expression levels. Combined treatment of A2780 cells with CX-4945 and cycloheximide revealed a faster rate of MDC1 degradation than with cycloheximide alone but did not affect MDC1 mRNA levels, indicating that CK2 regulates MDC1 protein stability. When combined with cisplatin, CX-4945 enhanced the activation of CHK2 and increased levels of γ-H2AX and cleaved PARP. In antiproliferative experiments, CX-4945 exhibited synergy with cisplatin in A2780 and SKOV3 cell lines. The combination of CX-4945 with cisplatin or carboplatin significantly enhanced antitumor activity in ovarian xenograft models and was well tolerated. Thus, the inhibition of CK2 by CX-4945 enhanced the antitumor activity of platinum agents by preventing DNA damage repair and inducing apoptosis. These data provide compelling preclinical support for pursuing CX-4945 in combination with platinum chemotherapy in the clinic. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5494. doi:10.1158/1538-7445.AM2011-5494

Protein kinase CK2 is necessary for the adipogenic differentiation of human mesenchymal stem cells

“…In the late phase of adipogenic 58 differentiation adipocyte specific proteins like perilipin, lipoprotein lipase, 59 glycerol phosphate dehydrogenase, leptin and adiponectin are expressed 60 which support the characteristics of an adipocyte phenotype [44]. 61 The activity of several signalling molecules and transcription factors 62 during differentiation is controlled by phosphorylation [27,33,68]. Also 63 the commitment of human mesenchymal stem cells to an osteogenic 64 or adipogenic lineage is regulated by protein kinases [26,28,34].…”

“…CK2 inhibitors CX-4945 and quinalizarin reduce CK2 activity in 302 non-differentiating human mesenchymal stem cells 303Over the last few years CK2 has been discovered as therapeutic 304 target for the treatment of cancer and several CK2 inhibitors have 305 been developed which are tested in ongoing clinical trials[61,62].…”

“…In order to study the inhibition of CK2 in human stem cells, we chose 311 the well-accepted CK2 inhibitor quinalizarin [9] and as a second inhibitor 312 CX-4945, which is currently investigated in clinical phase II trials as a 313 tumour therapeutic drug[61]. As the inhibition of such an essential kinase314 like CK2 might be fatal for the viability of cells, we first tested different 315 concentrations of the inhibitors in a viability assay.…”

Synergistic interactions of the anti-casein kinase 2 CIGB-300 peptide and chemotherapeutic agents in lung and cervical preclinical cancer models

“…Considering that CK2 phosphorylates critical substrates in this pathway (e.g., Akt, phosphatase and tensin homolog, p70SK6), the rationale behind such combination experiments was to reinforce the inhibitory effect of compounds such as erlotinib (epithelial growth factor receptor), LY294002 (PI3K) or the dual inhibitor PI-103 (PI3K and mTOR). Moreover, the combination of CX-4945 with cisplatin also resulted in a synergistic drug interaction in two ovarian cancer cell lines according to the Bliss additivity method (41,42). Beyond the fact that the methods of drug interaction analysis differ, those studies only evaluated particular drug concentrations in vitro, without providing an explanation for its selection or investigating a wide range of concentrations for each of the compounds (39,41).…”