Expression of Arl2 is associated with p53 localization and chemosensitivity in a breast cancer cell line

Abstract

In mammalian cells, ADP ribosylation factor like 2 (Arl2) has been shown to form a complex with tubulin binding cofactor D (TBC-D) and the tumor suppressor protein phosphatase 2A (PP2A). We have previously shown that alterations in Arl2 protein content were associated with corresponding modifications of the tumor suppressor PP2Ac protein content in breast cancer cells. Here, we show that modified Arl2 expression level influences sensitivity to various anticancer compounds such as taxol, navelbine, gemcitabine and doxorubicin in MCF7 derived cell lines. Modifications of Arl2 expression levels were also associated with an altered phosphorylation status and/or cellular sublocalization of certain PP2A targets such as p53, a key mediator of chemotherapy-induced apoptosis. A decreased level of Arl2 expression was associated with an increase of phospho-ser15-p53, a form which was found to be preferentially bound to microtubules. Assays using okadaic and cantharidic acid, two different PP2A inhibitors, showed an increase in microtubule-bound phospho-p53 and reduced sensitivity to chemotherapy. Our results suggest that Arl2 could, via PP2A, influence p53 phosphorylation status. Certain forms of phosphorylated p53 demonstrating increased binding to microtubules appear to be less prone to nuclear translocation after exposure to chemotherapeutic agents, thereby possibly contributing to reduced chemosensitivity.

Mutant p53 stimulates chemoresistance of pancreatic adenocarcinoma cells to gemcitabine

“…Our data is consistent with the observations that non-functional p53 affects the sensitivity of cancer cells to GEM [43] and that restoration of p53 function by various approaches in tumors allows activation of molecular pathways that improve the response to GEM [44,45]. Accordingly, some studies demonstrated that exposure to GEM enhances the transcriptional activity of p53 and that GEM-induced apoptosis in cancer cells is mediated by a p53-dependent transcriptional activation of cell death-related genes [46,47]. Here, we showed that the combined treatment of PDAC cells with GEM and p53-reactivating molecules (CP-31398 and RITA) synergistically inhibited cell proliferation in both wt and mp53 tumor cells but not in p53-null cancer cells ( Fig.…”

The ARL2 GTPase Is Required for Mitochondrial Morphology, Motility, and Maintenance of ATP Levels

“…When our latest observations are combined with earlier studies, we conclude that ARL2 is an important component of several cellular processes, including (i) regulation of ATP levels in mitochondria, likely in the matrix, (ii) regulation of mitochondrial fission and motility, (iii) at centrosomes, in concert with cofactor D, to regulate the growth of microtubules and mitotic spindles [10], [11], [22], [47], [76], (iv) in the nucleus to regulate STAT3 and perhaps other transcriptional responses [12], and in the cytosol to (v) regulate the folding of tubulin heterodimers [2], [3], and (vi) the shuttling and release of farnesylated proteins [24]. With the dissection of these different functions of ARL2 and the growing list of reagents allowing their clear resolution we are poised to understand the mechanisms of these actions at the molecular level, though some of them are expected to be challenging to document due to the limited understanding of the process itself (e.g., crista junction regulation).…”

“…In addition to changes in mitochondrial morphology, we also noted that cells deficient in ARL2 activity, either resulting from depletion by siRNA or expression of ARL2[T30N], appear to be smaller than controls. This size difference was not quantified or explored further in the current study but was reported earlier in related studies [10], [11], [22].…”

“…Mutations in both ARL2 and cofactor D have been identified in a number of genetic screens linked to microtubules in model organisms that include S. cerevisiae , S. pombe , A. thaliana , and C. elegans [4], [5], [6], [7], [8], [9]. Using stable variants of human breast adenocarcinoma lines, Beghin, et al [10],[11] showed that ARL2 protein content influences cell morphology (or cell spreading), soluble tubulin pools, microtubule dynamics, cell cycle progression, and chemosensitivity. ARL2 has also been proposed to regulate aspects of STAT3 signaling through actions in the nucleus [12].…”

Selective destabilization of tumor cells with pulsed electric and magnetic sequences: a preliminary report

“…Death observed in tumor cells but not in normal fibroblasts indicates that destabilization induced by MESQ was completely reversible or innocuous in cells with genomic stability and normal functions, including regulation and repair mechanisms, as already shown in various studies (Ali, 2007;Béghin et al, 2008;Hartwig et al, 2009). On the contrary, cells of the MCF7 tumor line, characterized by genomic instability, aneuploid chromosomes (hypertriploid-hypotetraploid), and aberrant cell function, were completely destabilized by MESQ, as shown by the large population of apoptotic cells after 3 h of exposure (Figs.…”