Open Access

Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide‑based glioblastoma chemotherapy

  • Authors:
    • Dong‑Ho Bak
    • Seong Hee Kang
    • Du Ri Choi
    • Mi Na Gil
    • Kwang Sik Yu
    • Ji Heun Jeong
    • Nam‑Seob Lee
    • Je‑Hun Lee
    • Young‑Gil Jeong
    • Dong Kwan Kim
    • Do‑Kyung Kim
    • Jwa‑Jin Kim
    • Seung‑Yun Han
  • View Affiliations

  • Published online on: March 24, 2016     https://doi.org/10.3892/etm.2016.3196
  • Pages: 2153-2162
  • Copyright: © Bak et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

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Abstract

Temozolomide (TMZ), an alkylating agent, is recommended as the initial treatment for high‑grade glioblastoma. TMZ is widely used, but its short half‑life and the frequency of tumor resistance limit its therapeutic efficacy. In the present study, the anticancer effect of vitamin D (VD) combined with TMZ upon glioblastoma was determined, and the underlying mechanism of this effect was identified. Through cell viability, clonogenic and wound healing assays, the current study demonstrated that treatment of a C6 glioblastoma cell line with TMZ and VD resulted in significantly increased in vitro antitumor effects compared with either VD or TMZ alone. Autophagy, hypothesized to be the dominant mechanism underlying TMZ‑based tumor cell death, was maximally activated in TMZ and VD co‑treated C6 cells. This was demonstrated by ultrastructural observations of autophagosomes, increased size and number of microtubule‑associated protein 1 light chain 3 (LC3) puncta and increased conversion of LC3‑I to LC3‑II. However, the extent of apoptosis was not significantly different between cells treated with TMZ and VD and those treated with TMZ alone. Addition of the autophagy inhibitor 3‑methyladenine markedly inhibited the anticancer effect of TMZ and VD treatment, indicating that the chemosensitizing effect of VD in TMZ‑based glioblastoma therapy is generated through enhancement of cytotoxic autophagy. TMZ and VD co‑treatment also significantly inhibited tumor progression and prolonged survival duration in rat glioblastoma orthotopic xenograft models when compared with TMZ treatment alone. These in vivo results are concordant with the aforementioned in vitro results, together revealing that the combined use of TMZ and VD exerts synergistic antitumor effects on rat models of glioblastoma and may represent an effective therapeutic strategy.
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June-2016
Volume 11 Issue 6

Print ISSN: 1792-0981
Online ISSN:1792-1015

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Copy and paste a formatted citation
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Spandidos Publications style
Bak DH, Kang SH, Choi DR, Gil MN, Yu KS, Jeong JH, Lee NS, Lee JH, Jeong YG, Kim DK, Kim DK, et al: Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide‑based glioblastoma chemotherapy. Exp Ther Med 11: 2153-2162, 2016
APA
Bak, D., Kang, S.H., Choi, D.R., Gil, M.N., Yu, K.S., Jeong, J.H. ... Han, S. (2016). Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide‑based glioblastoma chemotherapy. Experimental and Therapeutic Medicine, 11, 2153-2162. https://doi.org/10.3892/etm.2016.3196
MLA
Bak, D., Kang, S. H., Choi, D. R., Gil, M. N., Yu, K. S., Jeong, J. H., Lee, N., Lee, J., Jeong, Y., Kim, D. K., Kim, D., Kim, J., Han, S."Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide‑based glioblastoma chemotherapy". Experimental and Therapeutic Medicine 11.6 (2016): 2153-2162.
Chicago
Bak, D., Kang, S. H., Choi, D. R., Gil, M. N., Yu, K. S., Jeong, J. H., Lee, N., Lee, J., Jeong, Y., Kim, D. K., Kim, D., Kim, J., Han, S."Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide‑based glioblastoma chemotherapy". Experimental and Therapeutic Medicine 11, no. 6 (2016): 2153-2162. https://doi.org/10.3892/etm.2016.3196