Anti-tumor effects and cell motility inhibition of the DN604-gemcitabine combined treatment in human bladder cancer models

Abstract

Bladder cancer is one of the major tumors for men in the world, in which therapy the combination of cisplatin and gemcitabine is still fist-line applied to treat with advanced or metastatic bladder cancer. In our early study, we developed a potential Pt(II) agent, DN604, which has anti-tumor effect as potent as cisplatin toward bladder cancers. Herein, we aim at investigating the combinatory application of DN604 with gemcitabine for bladder cancer treatment. In vitro studies proved that the combined treatment of DN604 and gemcitabine could limit cell proliferation by elevating the incidence of DNA damage induced apoptosis. Notably, further researches showed that the DN604-gemcitabine treatment suppressed cell autophagy to inhibit cell motility upon the ROS dependent p38 MAPK signaling pathway, explicating its better anti-tumor activity than single drug treatment or the cisplatin-gemcitabine treatment. In vivo tests confirmed that the DN604-gemcitabine treatment has superior anti-tumor activity with low toxicity to cisplatin or its combination with gemcitabine treatments. DN604 plus gemcitabine, is of great significance for the treatment with human bladder cancer. Our study has provided a potential combination treatment option.

Introduction

Each year over 500,000 new cases are diagnosed and 200,000 patients die of bladder cancer worldwide, making it the fourth most common cancer in men.¹ At present, urothelial carcinomas remains one of the most common types in bladder cancer, while about 75% of patients have non-muscle invasive bladder cancer and 25% have muscle-invasive or metastatic disease.²

Although traditional Pt(II) agent, cisplatin, plus gemcitabine treatment has achieved good cure effect for bladder cancer, the invasive growing bladder tumors generally have poor prognosis. In spite of improved diagnostic and treatment strategies, the risk of recurrence after 5 years ranges over 50%.3, 4 Since cancer metastasis and failures to clinically treat metastases are responsible for the majority of patient deaths from solid tumors,5, 6 it is still necessary to find an efficient therapeutic method to inhibit tumor metastasis of bladder cancer. Cancer invasion, a complex process driven by cells and tissues, is triggered and maintained by the signaling pathways that control cytoskeletal dynamics, the transformation of cell-matrix and cell–cell connections, subsequent cell migration to adjacent tissue.7, 8 During the progression of the disease, physical, cellular and molecular determinants will adapt and react.⁹

It is well known that platinum-based compounds including cisplatin and carboplatin can target DNA and induce DNA damage.10, 11 As far as we know, reactive oxygen species (ROS), constantly produced and eliminated in biological systems, play important roles in a variety of normal biochemical functions and abnormal pathological processes. Evidences from extensive studies suggested that ROS can affect DNA damage response (DDR) and induce cell apoptosis.12, 13 More importantly, the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway is a general stress-activated kinase pathway, which relates to various intracellular stimulations including ROS. It has been reported that the activated-p38 MAPK signaling pathway has a close relationship to tumor invasion, which can induce cell apoptosis and suppress cell motility by inhibiting cell autophagy to solve the inevitable problem of tumor metastasis in bladder cancer treatments.14, 15, 16, 17

In previous studies, we designed a novel Pt(II)-based agent named DN604, which have been introduced a carbonyl group to the skeleton of 1,1-cyclobutanedicarboxylate based on the structure of carboplatin, exhibiting much stronger anti-tumor activity than carboplatin.¹⁸ On account of the combination of cisplatin and gemcitabine used to treat with advanced or metastatic bladder cancer, we herein report a new treatment by using DN604 to combine with gemcitabine to suppress cell motility and induce cell apoptosis. The in vitro and in vivo anti-tumor activity and the mechanism of such a combined therapy in human bladder cancer cells T24 were investigated.