Pathobiology of cigarette smoke-induced invasive cancer of the renal pelvis and its prevention by vitamin C.

Urothelial cancer of the renal pelvis (CRP) is predominantly associated with cigarette smoking. However, the molecular pathogenesis of initiation and progression of cigarette smoke (CS)-induced CRP is unknown. Majority of CRP is high grade and high stage at presentation and has a high recurrence rate even after surgery. Earlier we reported that prolonged treatment (24 weeks) of a guinea pig model with p-benzoquinone (p-BQ), a product of CS in vivo, produced carcinoma in situ in the renal pelvis, a noninvasive cancer. Since CS is known to induce invasive cancer, we investigated the effect of CS exposure to the guinea pigs. We observed that CS exposure for a short period (18 weeks) produced invasive tumor (pT1). pT1 was confirmed by immunohistochemistry showing increased immunoexpression of nuclear p53 indicating p53 mutation, aberrant CK20, increased Ki-67 and uniformly negative labeling of CD44. As observed earlier with p-BQ treatment, the initial events of CS exposure were oxidative damage and apoptosis that was followed by persistent signaling through EGFR and MAP kinase pathway. CS exposure also caused hyperphosphorylation of pRb, activation of cyclin E and cell cycle deregulation leading to infiltration of epithelial cells in lamina propria of the renal pelvis resulting in pT1 tumor. Oral supplementation of vitamin C (30 mg/kg guinea pig/day) inhibited oxidative damage and apoptosis and holistically prevented the tumor formation. We consider that our preclinical findings on the intake of adequate vitamin C, along with intense advice for cessation of smoking, will be helpful for the prevention of CS-induced CRP in smokers.

p-Benzoquinone initiates non-invasive urothelial cancer through aberrant tyrosine phosphorylation of EGFR, MAP kinase activation and cell cycle deregulation: Prevention by vitamin C.

According to WHO classification system, non-invasive urothelial carcinoma represents urothelial carcinoma in situ (CIS) and dysplasia. Dysplastic urothelium often progresses to CIS that further advances to urothelial carcinoma (UC). The strongest risk factor for UC is cigarette smoking. However, the pathogenesis of cigarette smoke (CS)-induced UC is poorly understood. Earlier we had shown that p-benzoquinone (p-BQ), a major toxic quinone derived from p-benzosemiquinone of CS in vivo, is a causative factor for various CS-induced diseases. Here, using a guinea pig model we showed that prolonged treatment with p-BQ led to non-invasive UC, specifically carcinoma in situ (CIS) of the renal pelvis and dysplasia in the ureter and bladder. The mechanisms of carcinogenesis were p-BQ-induced oxidative damage and apoptosis that were later suppressed and followed by activation of epidermal growth factor receptor, aberrant phosphorylation of intracellular tyrosine residues, activation of MAP kinase pathway and persistent growth signaling. This was accompanied by deregulation of cell cycle as shown by marked decrease in the expression of p21waf1/cip1 and cyclin D1 proteins as well as hyperphosphorylation of pRb. UC has been characterised by histopathology and immunohistochemistry showing aberrant CK20, increased Ki-67, and marked p53 nuclear immunopositivity with uniformly negative labelling of CD44. Oral supplementation of vitamin C (30 mg/kg body weight/day) prevented CIS of the renal pelvis and dysplasia in the ureter and bladder. Since majority of non-invasive UC progresses to invasive cancer with increased risk of mortality, our preclinical study might help to devise effective strategies for early intervention of the disease.

Causation of cigarette smoke-induced emphysema by p-benzoquinone and its prevention by vitamin C.

Cigarette smoke (CS) is the strongest risk factor for emphysema. However, the mechanism of the disease is not clear. One reason is that each puff of CS is a complex mixture of approximately 4,000 chemicals, and it is yet to be known which of these chemical(s) are directly involved in the pathogenesis of lung injury in emphysema. The purpose of this study was to demonstrate that p-benzoquinone (p-BQ) produced in the lungs of CS-exposed guinea pigs is a causative factor for destruction of alveolar cells resulting in emphysema that is prevented by vitamin C. Vitamin C-restricted guinea pigs were subjected to whole-body CS exposure from five Kentucky research cigarettes (3R4F) per day or intramuscular injection of p-BQ in amounts approximately produced in the lung from CS exposure with and without oral supplementation of vitamin C. Progressive exposure of CS or p-BQ treatment caused progressive accumulation of p-BQ in the lung that was accompanied by destruction of alveolar cells and emphysema. The pathogenesis involved was arylation, oxidative stress, inflammation, and apoptosis. Vitamin C (30 mg/kg body weight/d), a potential antagonist of p-BQ, prevented accumulation of p-BQ in the lung and the pathogenesis of emphysema. Our study provides the first proof that inactivation of p-BQ, a causative factor of emphysema in CS-exposed lung, could constitute a novel and effective approach in the prevention of emphysema. We consider that a moderately high dose of vitamin C may be a simple preventive therapy for emphysema in chronic smokers.