CK2 inhibition with silmitasertib promotes methuosis-like cell death associated to catastrophic massive vacuolization of colorectal cancer cells

Abstract

Protein kinase CK2 is a highly conserved and constitutively active Ser/Thr-kinase that phosphorylates a large number of substrates, resulting in increased cell proliferation and survival. A known target of CK2 is Akt, a player in the PI3K/Akt/mTORC1 signaling pathway, which is aberrantly activated in 32% of colorectal cancer (CRC) patients. On the other hand, mTORC1 plays an important role in the regulation of protein synthesis, cell growth, and autophagy. Some studies suggest that CK2 regulates mTORC1 in several cancers. The most recently developed CK2 inhibitor, silmitasertib (formerly CX-4945), has been tested in phase I/II trials for cholangiocarcinoma and multiple myeloma. This drug has been shown to induce autophagy and enhance apoptosis in pancreatic cancer cells and to promote apoptosis in non-small cell lung cancer cells. Nevertheless, it has not been tested in studies for CRC patients. We show in this work that inhibition of CK2 with silmitasertib decreases in vitro tumorigenesis of CRC cells in response to G2/M arrest, which correlates with mTORC1 inhibition and formation of large cytoplasmic vacuoles. Notably, molecular markers indicate that these vacuoles derive from massive macropinocytosis. Altogether, these findings suggest that an aberrantly elevated expression/activity of CK2 may play a key role in CRC, promoting cell viability and proliferation in untreated cells, however, its inhibition with silmitasertib promotes methuosis-like cell death associated to massive catastrophic vacuolization, accounting for decreased tumorigenicity at later times. These characteristics of silmitasertib support a potential therapeutic use in CRC patients and probably other CK2-dependent cancers.

Phosphorylation of Endothelin-Converting Enzyme-1c at Serines 18 and 20 by CK2 Promotes Aggressiveness Traits in Colorectal Cancer Cells

“…Cytometric analysis showed no significant differences in S and G2/M populations for all cells treated with 5-FU. However, the biphospho-resistant ECE1c AA -expressing cells experimented a dramatical increase in subG 0 population (Figure 5), indicating the onset of apoptosis-related death upon treatment with 5-FU, as suggested by our published results with another apoptosis-inducing drug in the same cells (18). In contrast, the biphospho-mimetic ECE1c DD -expressing cells displayed the lowest % of subG 0 population.…”

Role of CK2 inhibitor CX-4945 in anti-cancer combination therapy – potential clinical relevance

“…Finally, it is to be mentioned that CX-4945 has recently been characterized as a methuosis inducer, a new issue that could be relevant in anti-cancer combination therapy. When used at high micromolar concentrations, ranging from 10 to 50 μM, CX-4945 promotes a distinctive form of cell death characterized by displacement of large, macro-pinocytic-derived and fluid-filled cytosolic vacuoles, that has been dubbed methuosis (from the Greek word μεθύω, to be drunk) [93][94][95]. We and others have previously reported that the induction of methuosis mediated by CX-4945, as well as its derivative CX-5011, is CK2-independent [93,95].…”

Multiple cell death modalities and their key features (Review)

“…The massive vacuoles, which are not able to be recycled or merged with lysosomes, will finally lead to cell death. Methuosis with its typical morphology, is often assessed by electron microscopy in research (36)(37)(38) (Table I).…”