Resistance to discodermolide, a microtubule-stabilizing agent and senescence inducer, is 4E-BP1–dependent

Abstract

Discodermolide is a microtubule-stabilizing agent that induces accelerated cell senescence. A discodermolide-resistant cell line, AD32, was generated from the human lung cancer cell line A549. We hypothesize that the major resistance mechanism in these cells is escape from accelerated senescence. AD32 cells have decreased levels of 4E-BP1 mRNA and protein, relative to the parental discodermolide-sensitive A549 cells. Lentiviral-mediated re-expression of wild-type 4E-BP1 in AD32 cells increased the proliferation rate and reverted resistance to discodermolide via restoration of discodermolide-induced accelerated senescence. Consistent with this, cell growth and response to discodermolide was confirmed in vivo using tumor xenograft models. Furthermore, reintroduction of a nonphosphorylatable mutant (Thr-37/46 Ala) of 4E-BP1 was able to partially restore sensitivity and enhance proliferation in AD32 cells, suggesting that these effects are independent of phosphorylation by mTORC1. Microarray profiling of AD32-resistant cells versus sensitive A549 cells, and subsequent unbiased gene ontology analysis, identified molecular pathways and functional groupings of differentially expressed mRNAs implicated in overcoming discodermolide-induced senescence. The most statistically significant classes of differentially expressed genes included p53 signaling, G2/M checkpoint regulation, and genes involved in the role of BRCA1 in the DNA damage response. Consistent with this, p53 protein expression was up-regulated and had increased nuclear localization in AD32 cells relative to parental A549 cells. Furthermore, the stability of p53 was enhanced in AD32 cells. Our studies propose a role for 4E-BP1 as a regulator of discodermolide-induced accelerated senescence. drug resistance | senescence reversion | TOR signaling

4E-BP1 participates in maintaining spindle integrity and genomic stability via interacting with PLK1

“…36 Discodermolide is a microtubule-stabilizing agent that induces accelerated cell senescence, and it has recently been shown that reintroduction of 4E-BP1 even a nonphosphorylatable mutant (Thr-37/46 Ala) of 4E-BP1 can revert the resistance of the 4E-BP1-defective cancer cells to discodermolide via restoration of induced accelerated senescence. 37 Our data here showed that depression of 4E-BP1 sensitized HepG2 cells to paclitaxel, and which is partially attributed to the increased induction of apoptosis. Although depletion of 4E-BP1 also sensitizes HeLa cells to paclitaxel, no significant apoptosis was induced in response to paclitaxel treatment even with the knowdown of 4E-BP1.…”

Cellular senescence and cancer chemotherapy resistance

“…The investigators then showed that a subset of cells were able to escape senescence and that those escaping cells were more resistant to chemotherapeutics than the parental cells. Further support for this idea was reported by Chao et al (Chao et al, 2011) when they found that resistance to the microtubule-stabilizing agent Discodermolide in a subset of lung carcinoma cells was linked to the emergence from senescence and possibly mediated by alterations in the expression of 4E-BP1. The different escape routes observed might suggest that each cell population invokes unique mechanisms that allow for breaking senescence.…”

Improved Dose-Response Relationship of (+)-Discodermolide-Taxol Hybrid Congeners

“…Ten cell lines were used in this study as detailed: MDA-MB-468, BT20, HCC1143, HS578T, BT549, MDA-MB-157 (TNBC breast), MCF7 (ER+ breast), HEY (serous ovarian), A549, and its (+)-discodermolide-resistant variant, AD32 2 (K-RAS mutant NSCLC). All cell lines were purchased from the American Type Culture Collection, unless otherwise stated, and maintained in RPMI medium (HyClone) supplemented with 10% fetal bovine serum (Gibco).…”