Microtubule-targeting agents augment the toxicity of DNA-damaging agents by disrupting intracellular trafficking of DNA repair proteins

Abstract

The paradigm that microtubule-targeting agents (MTAs) cause cell death via mitotic arrest applies to rapidly dividing cells but cannot explain MTA activity in slowly growing human cancers. Many preferred cancer regimens combine a MTA with a DNA-damaging agent (DDA). We hypothesized that MTAs synergize with DDAs by interfering with trafficking of DNA repair proteins on interphase microtubules. We investigated nine proteins involved in DNA repair: ATM, ATR, DNA-PK, Rad50, Mre11, p95/NBS1, p53, 53BP1, and p63. The proteins were sequestered in the cytoplasm by vincristine and paclitaxel but not by an aurora kinase inhibitor, colocalized with tubulin by confocal microscopy and coimmunoprecipitated with the microtubule motor dynein. Furthermore, adding MTAs to radiation, doxorubicin, or etoposide led to more sustained γ-H2AX levels. We conclude DNA damage-repair proteins traffic on microtubules and addition of MTAs sequesters them in the cytoplasm, explaining why MTA/DDA combinations are common anticancer regimens.

Antiproliferative activity of chloroformic fractions from leaves and inflorescences of Ageratina gracilis

“…The number of cells in Sub-G1 not exceed 2% during 72 hours of incubation. Vincristine sulfate, as expected, produced an arrest in G2/M phase of the cell cycle of A549 cells, avoiding cell proliferation and hence causing cell death (Poruchynsky et al, 2015), as was evidenced in a time dependent manner of drug treatment. Instead, the chloroformic fraction from petroleum ether extract of inflorescences, chloroformic fraction from petroleum ether extract of leaves and chloroformic fraction from ethanolic extract of leaves, caused cell growth inhibition of A549 cells by blocking the G1 phase to S phase in the cell cycle (Fig.…”

High-throughput screening in niche-based assay identifies compounds to target preleukemic stem cells

“…Recent evidence suggests an important nonmitotic function of 2-ME2, in preventing the nuclear accumulation of transcription factors or DNA repair proteins (41,42). We therefore quantitated SCL at the single-cell level by flow cytometry and found that 2-ME2 caused a dose-dependent inhibition of the human SCL oncoprotein in SCL tg LMO1 tg pre-LSCs ( Figure 4C).…”

Cell Cycle–Dependent Mechanisms Underlie Vincristine-Induced Death of Primary Acute Lymphoblastic Leukemia Cells

“…One study showed that in prostate cancer cells, taxanes act, at least in part, by inhibiting nuclear transport of the androgen receptor (AR), and hence block AR-mediated signaling [34]. It was also recently reported that MTAs interfere with the trafficking of DNA repair proteins on interphase microtubules, providing a mechanistic explanation for the long-standing observation that MTAs and DNA damaging agents act synergistically [35]. We observed that the induction of apoptosis in primary ALL cells in G1 phase was not initiated until 24 h after vincristine treatment (Fig.…”