Hypothesis Explaining Development of Squamous Cell Carcinoma During Infection with Schistosoma Haematobium

Abstract

Schistosome worms are blood-dwelling flukes that cause chronic infection in more than 200 million people and are thought to be responsible for 500,000 deaths annually. During infection with Schistosoma haematobium, eggs are deposited in the mucosa and submucosa of the bladder and lower ureters. Squamous cell carcinoma (SCC) of the bladder is a long-term sequela of chronic infection. The mechanisms underlying the association between S. haematobium and SCC of the bladder are largely unknown, with all reports to date exclusively demonstrating epidemiological evidence linking S. haematobium infection with SCC of the bladder. Scientists hypothesised that the parasite antigens might induce alterations in epithelial cells towards cancer. Scientists used Chinese Hamster Ovary (CHO) cells and treated the cells in culture with S. haematobium total antigen (Sh). Results showed increased proliferation, increased S-phase and decreased apoptosis, as well as down-regulation of tumor suppressor p27 and up-regulation of anti-apoptotic molecule Bcl-2 (Botelho et al., 2009). Angiogenesis is defined as the formation of new blood vessels from preexisting ones and is recognized as a key event in cell proliferation and carcinogenesis and spread of malignant lesions (Dematei et al., 2017). S. haematobium is classified as a Group 1 carcinogen by the World Health Organization’s International Agency for Research on Cancer (Hodderet al., 2000). Another factor that may play a major role in bladder carcinogenesis in schistosomiasis patients is the presence of continuous physical irritation and inflammation produced by Schistosoma eggs in the bladder mucosa. The adult S. haematobium worms inhabit the veins of the perivesical plexus, where the female lays eggs. Some eggs pass through the bladder mucosa and are excreted in the urine. Other eggs are trapped in the tissue. A chronic inflammatory reaction is initiated, with the invasion of histiocytes and other inflammatory cells into the bladder, the formation of granulomas and eventually fibrosis. In addition, the eruption of the eggs through the mucosa stimulates reparative urothelial hyperplasia and cell turnover (Rosin et al., 1994). In our article we try to explain possible mechanism of conversion normal cells into tumor cells from the position of karyogamic theory.