Bladder cancer is the tenth most common cancer worldwide and the sixth most common cancer in men. General symptoms include hematuria and painful urination. Regular smokers are 4-6 times more likely to develop bladder cancer than the general population. Clinically, cystectomy is commonly used in the treatment of muscle-invasive bladder cancer. However, not only does this disturb the patient's daily life, it may also affect prognosis and survival after surgery. Therefore, current research has shifted the focus to alternative therapies for bladder preservation. Bladder cancer can be divided into five stages according to the degree of cancer cell invasion of the bladder wall: from the mildest stage 0 to the most serious stage 4. Mild superficial bladder cancer is only in the mucosal layer of the bladder and has a better prognosis, while more malignant deep bladder cancer has already invaded the muscle layer or may have metastasized to other organs. Treatment with pterostilbene (PT) can induce the activation of cellular caspase-3 through internal and external pathways, and activate the expression of pro-apoptotic proteins and downstream apoptotic pathways. Moreover, in the research of genetic data of bladder cancer cells, it founded that PT regulates different signal transduction pathways and promote the changes of growth inhibition, apoptosis and cell cycle regulation in sensitive and drug-resistant bladder cancer cells. However, PT still has some shortcomings compared with the drugs actually used in clinical treatment, so further research is needed.

In this study, we used two types of human HTB-9 (primary carcinoma) and T24 (transitional cell carcinoma) bladder cancer cell lines, which representing different disease processes (mild and malignant) for PT detecting. CCK8 detection and flow cytometry were used to observe cell survival rate and cell apoptosis rate. We further observed the changes in the signal transduction pathway that induced apoptosis to depict the detailed mechanism of PT in inducing apoptosis of different bladder cancer cells.

Our research results showed that PT can indeed inhibit the growth of HTB-9 bladder cancer cells, which is significantly different from SV-HUC-1 cells, but the effect on T24 cancer cells is less significant. This study explored the differences in the apoptosis pathways of the two cancer cells, and showed that PT had no significant apoptotic effect on T24 under short-term and low-dose conditions, but increasing the dose and extending the time could enhance the mortality rate and apoptosis ratio. The results of qPCR and Western blot also showed a trend of apoptosis-related proteins, echoing the effect of PT on T24.

The study reveals the possible role and potential of PT in the apoptosis of different types of bladder cancer cells, increase clinical drug applications, and provide a research basis for the development of new anti-bladder cancer drugs.