Norcantharidin Induced DU145 Cell Apoptosis through ROS-Mediated Mitochondrial Dysfunction and Energy Depletion

Bo Shen,Chun-Lin Shao,Pei-Jie He,Partha Mukhopadhyay

doi:10.1371/journal.pone.0084610

Abstract

Norcantharidin (NCTD), a demethylated analog of cantharidin derived from blister beetles, has attracted considerable attentions in recent years due to their definitely toxic properties and the noteworthy advantages in stimulating bone marrow and increasing the peripheral leukocytes. Hence, it is worth studying the anti-tumor effect of NCTD on human prostate cancer cells DU145. It was found that after the treatment of NCTD with different concentrations (25-100 μM), the cell proliferation was significantly inhibited, which led to the appearance of micronucleus (MN). Moreover, the cells could be killed in a dose-/ time-dependent manner along with the reduction of PCNA (proliferating cell nuclear antigen) expression, destruction of mitochondrial membrane potential (MMP), down-regulation of MnSOD, induction of ROS, depletion of ATP, and activation of AMPK (Adenosine 5‘-monophosphate -activated protein kinase) . In addition, a remarkable release of cytochrome c was found in the cells exposed to 100 μM NCTD and exogenous SOD-PEG could eliminate the generation of NCTD-induced MN. In conclusion, our studies indicated that NCTD could induce the collapse of MMP and mitochondria dysfunction. Accumulation of intercellular ROS could eventually switch on the apoptotic pathway by causing DNA damage and depleting ATP.

Highlights

Prostate cancer (PCa) was the sixth leading cause of male cancer death in the western developed countries [1,2]
NCTD inhibited the growth of DU145 cells As shown in Figure 1A, when DU145 cells were exposed to NCTD with various concentrations from 25 to 400 μM for 24h, the cell proliferation was inhibited in a dose-/time- dependent manner
When DU145 cells were incubated with 25 μM NCTD for 24 h, 48 h and 72 h, the corresponding proliferation inhibition rates were increased to 12.91 %, 33.14 % and 61.26%, respectively (Figure 1B)

Summary

Introduction

Prostate cancer (PCa) was the sixth leading cause of male cancer death in the western developed countries [1,2]. After about 1-3 years of treatment period, almost all tumors will eventually develop to castration-resistant PCa (CRPC) with the distant metastases and a poor prognosis [4]. How to achieve a satisfied regression on prostate cancer under androgen-deprived conditions, still remains a challenge for the effective treatment of PCa. Cantharidin is a natural toxin extracted from blister beetles. Cantharidin has been demonstrated the inhibitory effects on protein phosphatases type 2A (PP2A), which is a ubiquitous and conserved serine/threonine phosphatase with broad substrate specificity and diverse cellular functions [6,7]. It has been demonstrated that NCTD could inhibit the proliferation and induce apoptosis in several tumor cells, such as leukemic cells, gallbladder carcinoma cells, and colorectal cancer cells [11,12,13]. Due to stimulating bone marrow and increasing the peripheral leukocytes, NCTD may be a potential chemotherapeutic agent in cancer treatment [17]

Methods

Results

Conclusion