Abstract

Simple SummaryCombined treatments with low side effects enhance anticancer applications. This study focusses on validating the potential synergistic antiproliferation of the combined treatment of ultraviolet-C and the coral-derived compound sinularin (UVC/sinularin) in oral cancer cells. This study confirms that UVC/sinularin synergistically and selectively inhibits oral cancer cell proliferation with low cytotoxicity on normal oral cells. The mechanisms involve the enhanced cellular and mitochondrial oxidative stress that cause apoptosis, DNA damage, and mitochondrial dysfunction in oral cancer cells.Combined treatment is increasingly used to improve cancer therapy. Non-ionizing radiation ultraviolet-C (UVC) and sinularin, a coral Sinularia flexibilis-derived cembranolide, were separately reported to provide an antiproliferation function to some kinds of cancer cells. However, an antiproliferation function using the combined treatment of UVC/sinularin has not been investigated as yet. This study aimed to examine the combined antiproliferation function and explore the combination of UVC/sinularin in oral cancer cells compared to normal oral cells. Regarding cell viability, UVC/sinularin displays the synergistic and selective killing of two oral cancer cell lines, but remains non-effective for normal oral cell lines compared to treatments in terms of MTS and ATP assays. In tests using the flow cytometry, luminescence, and Western blotting methods, UVC/sinularin-treated oral cancer cells exhibited higher reactive oxygen species production, mitochondrial superoxide generation, mitochondrial membrane potential destruction, annexin V, pan-caspase, caspase 3/7, and cleaved-poly (ADP-ribose) polymerase expressions than that in normal oral cells. Accordingly, oxidative stress and apoptosis are highly induced in a combined UVC/sinularin treatment. Moreover, UVC/sinularin treatment provides higher G2/M arrest and γH2AX/8-hydroxyl-2′deoxyguanosine-detected DNA damages in oral cancer cells than in the separate treatments. A pretreatment can revert all of these changes of UVC/sinularin treatment with the antioxidant N-acetylcysteine. Taken together, UVC/sinularin acting upon oral cancer cells exhibits a synergistic and selective antiproliferation ability involving oxidative stress-dependent apoptosis and cellular DNA damage with low toxic side effects on normal oral cells.

Highlights

  • Radiation and chemotherapy are the routine remedies for oral cancer therapy [1]

  • NAC rescues the antiproliferation of sinularin and UVC/sinularin treatments in both oral cancer cell lines, NAC shows different responses to UVC

  • NAC rescues the mild antiproliferation to normal oral cells

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Summary

Introduction

Radiation and chemotherapy are the routine remedies for oral cancer therapy [1]. The problems of radio- and chemo-resistance, and their associated side effects, may weaken their anticancer applications in oral cancer therapies [2,3,4]. Combined treatment with natural products provides an improved strategy to overcome radio- and chemo-resistance or side effects in cancer therapy [5,6]. For the complex etiology and targeting of cancer, combinations of anticancer drugs, natural products and radiation are increasingly used to improve the therapeutic efficiency for oral cancer [7,8]. The combined treatments of clinical drugs [13,14], chemical agents [15], or natural products [16,17]

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