Vasculogenic mimicry in bladder cancer and its association with cancer stem cells and human chorionic gonadotropin-beta

Bladder cancer is the 11th most common cancer in the United Kingdom and it is the fourth most common cancer in men. It has been found that some cancerous tumours acquire resistance to antiangiogenic therapy due to different angiogenic “escape “ pathways that allow tumours to restore their growth and hence can invade and metastasise. Vascular mimicry is the process of formation of tumour cell lined channels for nutrient transportation, independent of typical modes of angiogenesis. However, not much research has been done to investigate the occurrence of vascular mimicry (VM) in bladder cancer or to correlate the presence of VM with different stages and grades of bladder cancer. Equally, the prevalence of cancer stem cells (CSCs) in bladder cancer in relation to the different grades and stages has not been studied as well as their relationship with VM.
Additionally, several studies have demonstrated the involvement of human chorionic gonadotrophin-beta (hCG-beta) in the development of VM in some types of cancer such as ovarian cancer, cervical cancer, testicular cancer and hepatocellular carcinoma. However, there is not much research performed on the role of hCG-beta in the initiation of VM in bladder cancer. Therefore, as the main aim of this study, investigated the occurrence of VM in bladder cancer and assessed its presence in the different stages and grades of bladder cancer. The incidence of cancer stem cells in the different grades and stages of bladder transitional cell carcinoma was examined and their relationship with VM was evaluated. The possible involvement of hCG-beta in initiating VM channel formation was assessed in vitro using T24 and ScaBER bladder cancer cell lines.
VM channels were identified on transitional cell carcinoma bladder cancer tissue using double staining technique with endothelial cell marker CD31 and periodic acid Schiff’s (PAS) and the statistical analysis showed that there was a significant association between stages (P=0.038) of bladder cancer and the presence of VM. However, there was no significant association between grades of bladder cancer and vascular mimicry (P=0.154). Moreover, statistical analysis revealed that there was a negative correlation between vascular mimicry and mean vascular density value.
Cancer stem cells were identified on transitional cell carcinoma bladder cancer tissue using immunohistochemical staining with stem cell marker CD133 and the statistical analysis demonstrated that there was no significant association between stages (P=0.315) and grades (P=0.216) of bladder cancer and cancer stem cells. Furthermore, statistical analysis demonstrated that there was a positive correlation (r= 0.380) between cancer stem cells and vascular mimicry.
In addition, immunocytochemistry and western blot techniques were used to detect vascular mimicry channel formation in 2D and 3D bladder cancer culture models using endothelial markers CD31 and laminin before and after treatment with recombinant human chorionic gonadotrophin-beta. In vitro studies using 3D models of bladder cancer showed an increased expression of VM markers CD31 and laminin when treated with recombinant hCG-beta. This upregulated vascular mimicry markers expression suggests an impact of human chorionic gonadotropin-beta on VM formation.
Identification of signalling pathways that are involved in VM formation and the involvement of hCG-beta in inducing VM can aid in identifying a therapeutic target for bladder cancer patients. The positive correlation between cancer stem cells and VM suggests that cancer stem cells may play a role in initiating the formation of VM. Hence, signalling pathways that control cancer stem cell differentiation may also be a potential therapeutic target to improve bladder cancer patients prognosis.