Tenuifolide B from Cinnamomum tenuifolium Stem Selectively Inhibits Proliferation of Oral Cancer Cells via Apoptosis, ROS Generation, Mitochondrial Depolarization, and DNA Damage

Abstract

The development of drugs that selectively kill oral cancer cells but are less harmful to normal cells still provide several challenges. In this study, the antioral cancer effects of tenuifolide B (TFB), extracted from the stem of the plant Cinnamomum tenuifolium are evaluated in terms of their effects on cancer cell viability, cell cycle analysis, apoptosis, oxidative stress, and DNA damage. Cell viability of oral cancer cells (Ca9-22 and CAL 27) was found to be significantly inhibited by TFB in a dose-responsive manner in terms of ATP assay, yielding IC50 = 4.67 and 7.05 μM (24 h), but are less lethal to normal oral cells (HGF-1). Dose-responsive increases in subG1 populations as well as the intensities of flow cytometry-based annexin V/propidium iodide (PI) analysis and pancaspase activity suggested that apoptosis was inducible by TFB in these two types of oral cancer cells. Pretreatment with the apoptosis inhibitor (Z-VAD-FMK) reduced the annexin V intensity of these two TFB-treated oral cancer cells, suggesting that TFB induced apoptosis-mediated cell death to oral cancer cells. Cleaved-poly (ADP-ribose) polymerase (PARP) and cleaved-caspases 3, 8, and 9 were upregulated in these two TFB-treated oral cancer cells over time but less harmful for normal oral HGF-1 cells. Dose-responsive and time-dependent increases in reactive oxygen species (ROS) and decreases in mitochondrial membrane potential (MitoMP) in these two TFB-treated oral cancer cells suggest that TFB may generate oxidative stress as measured by flow cytometry. N-acetylcysteine (NAC) pretreatment reduced the TFB-induced ROS generation and further validated that ROS was relevant to TFB-induced cell death. Both flow cytometry and Western blotting demonstrated that the DNA double strand marker γH2AX dose-responsively increased in TFB-treated Ca9-22 cells and time-dependently increased in two TFB-treated oral cancer cells. Taken together, we infer that TFB can selectively inhibit cell proliferation of oral cancer cells through apoptosis, ROS generation, mitochondrial membrane depolarization, and DNA damage.

4β‐Hydroxywithanolide E selectively induces oxidative DNA damage for selective killing of oral cancer cells

“…Normal cells can tolerate a certain level of ROS modulating drug‐induced oxidative stress; however, ROS‐modulating drugs can increase ROS above the threshold of redox homeostasis in cancer cells, resulting in cell death . Therefore, several ROS modulating drugs and natural products have been developed to achieve oxidative stress‐based selective cell killing for anticancer therapy …”

“…Given differential responses of ROS modulating drugs and natural products between cancer and normal cells, selective DNA damage for selective apoptosis and killing may occur in cancer cells. For example, Cinnamomum tenuifolium stem‐derived tenuifolide B selectively killed oral cancer cells via ROS‐mediated selective apoptosis and DNA damage . Specifically, ROS may induce oxidative DNA damage .…”

“…2 Therefore, several ROS modulating drugs and natural products have been developed to achieve oxidative stressbased selective cell killing for anticancer therapy. [3][4][5][6][7][8] Excessive ROS may induce DNA damage 9 resulting in cancer cell apoptosis. 10,11 Given differential responses of ROS modulating drugs and natural products between cancer and normal cells, 1 selective DNA damage for selective apoptosis and killing may occur in cancer cells.…”

“…For example, Cinnamomum tenuifolium stem-derived tenuifolide B selectively killed oral cancer cells via ROS-mediated selective apoptosis and DNA damage. 5 Specifically, ROS may induce oxidative DNA damage. 12 8-Oxo-2 0 deoxyguanosine (8-oxodG) is one of the most common products of oxidative DNA damage as a biomarker for oxidative stress.…”

Isocordoin analogues promote apoptosis in human melanoma cells via Hsp70

“…ROS have been reported to be involved in cell death induced by a variety of stimuli (Chen et al, ). Therefore, we examined whether tested molecule‐induced cell death may result from an elevation of ROS.…”