Histone deacetylase inhibitors and paclitaxel cause synergistic effects on apoptosis and microtubule stabilization in papillary serous endometrial cancer cells

Abstract

The use of histone deacetylase (HDAC) inhibitors has shown promise for a variety of malignancies. In this investigation, we define the activity of this class of inhibitors in combination with traditional cytotoxic chemotherapy in endometrial cancer cells. Significant reductions in growth were observed in Ark2 and KLE endometrial cancer cells following treatment with paclitaxel, doxorubicin, carboplatin, or the HDAC inhibitor trichostatin A (TSA). However, only combined treatment with TSA/paclitaxel caused synergistic inhibition of cell growth. This combination also resulted in significant changes in cell morphology. Using cell cycle analysis, nuclear staining, and Western blot analysis for poly(ADPribose) polymerase and caspase-9 degradation products, TSA/paclitaxel showed the most dramatic activation of the apoptotic cascade. These effects were also observed when the HDAC inhibitors HDAC inhibitor-1 or oxamflatin were substituted for TSA. The anticancer properties of paclitaxel are known to result in part from inhibition of microtubule depolymerization, which results in apoptosis. We show that TSA administration also stabilizes microtubules via A-tubulin acetylation. Furthermore, using Western blot and immunohistochemical analysis, treatment with TSA/paclitaxel led to a significant increase in acetylated tubulin and microtubule stabilization. These effects were confirmed in a mouse xenograft model. Moreover, TSA/paclitaxel resulted in a 50% reduction in tumor weight compared with either agent alone. This study provides in vivo evidence of nonhistone protein acetylation as one possible mechanism by which HDAC inhibitors reduce cancer growth. The TSA/paclitaxel combination seems to hold promise for the treatment of serous endometrial carcinoma and other malignancies with limited sensitivity to paclitaxel.

Belinostat and vincristine demonstrate mutually synergistic cytotoxicity associated with mitotic arrest and inhibition of polyploidy in a preclinical model of aggressive diffuse large B cell lymphoma

“…58 Synergy between taxanes and HDACi in inducing cytotoxicity has been previously demonstrated in vitro and in xenograft tumor models of ovarian, breast, and prostate cancer. 30,[59][60][61][62][63][64][65][66][67][68] Belinostat has been found to be synergistic with taxanes in inducing apoptosis in prostate and ovarian cell lines and in clinical samples from ovarian tumors grown in organoid culture. 65,67 Although most of these studies did not explore mechanism, cytotoxicity induced by vorinostat and paclitaxel in breast cancer cell lines was accompanied by increased induction of G2/M arrest.…”

Microtubule acetylation and stability may explain alcohol-induced alterations in hepatic protein trafficking

“…Values are the average Ϯ SEM of at least 3 independent experiments; * P Ͻ 0.03; † P Ͻ 0.0001. peared independent of microtubule stability, 16,20,21 whereas in other studies including this one, increased acetylation induced increased microtubule stability. [13][14][15] The reasons for these conflicting results are not known but may reflect cell type differences in microtubule dynamics. Also, different assays were used to determine stability that likely vary in sensitivity and approach (for example, measuring nocodazole resistance versus real-time tubulin dynamics) such that conflicting results were obtained.…”

“…HDAC6 is the major tubulin deacetylase in liver and WIF-B cells (Grozinger et al 12 and manuscript in preparation), and when inhibited with TSA, increased microtubule acetylation and stability is observed. [13][14][15] We determined that 50 nM TSA for 30 minutes induced microtubule acetylation and stability to the same extent in WIF-B cells as did ethanol, allowing us to test our hypothesis. This result also suggested that acetylation induced microtubule stability, a topic that is currently controversial (for example, see Tran et al 15 and Palazzo et al 16 and the Discussion section).…”

Will histone deacetylase inhibitors require combination with other agents to fulfil their therapeutic potential?

“…With regard to underlying mechanisms, in endometrial cancer cell lines, TSA administration induced a-tubulin acetylation and appeared to stabilise microtubules. Combination with paclitaxel led to a significant increase in acetylated tubulin and microtubule stabilisation above that with either agent alone (Dowdy et al, 2006). These data show a clear rationale for combining HDIs with a range of chemotherapeutic agents, but that clinical trials must be underpinned by a clear mechanistic rationale specific to both experimental agents and tumour types.…”

“…Synergistic reductions in growth were seen in endometrial cancer cells following treatment with paclitaxel combined with the HDI trichostatin A (TSA), and this was confirmed in mouse xenograft studies (Dowdy et al, 2006). Synergistic interaction was also seen in breast cancer cells combining docetaxel with vorinostat (Bali et al, 2005).…”