4-nitroquinoline 1-oxide induces immune cells death to onset early immunosuppression during oral squamous cell carcinoma development.

4-Nitroquinoline N-oxide (4-NQO) and its derivatives react with genomic DNA to form stable quinolone monoadducts, which are highly mutagenic and genotoxic. While the chronic high-dose exposure of epithelial cells to a carcinogen such as 4-NQO leads to tumor development, its effect on other cells has not been explored yet. Since the immunosuppression due to aberrant immunological profile is recognized as a significant cause in tumors, here we determine the interaction between 4-NQO and immune cells both in vivo and in vitro, and its effect on oral squamous cell carcinoma (OSCC) progression in a murine model. Immune cell profiling of the spleen and peripheral blood revealed a significant decrease in the B-cell population in 4-NQO-exposed mice than the untreated group. Additionally, γδ T and CD5+ B lymphocyte populations decreased at both pre- and post-cancerous stages of OSCC. These results suggested that 4-NQO induced tumor transition from pre-malignant lesions to OSCC by altering certain immune cells systemically. Next, to establish the effect of 4-NQO on immune cells, human B- and T-cell lines were subjected to 4-NQO; the reduction in cell viability, increase in DNA damage response marker, and induction of apoptosis were more pronounced in B than T cells. Altogether, our results indicated that in addition to the genotoxicity of oral epithelial cells, 4-NQO potentiates long-range effects on specific immune cells to induce cell death to cause very-early immunosuppressive response during oral carcinogenesis, and thus immunosuppression and tumor development are coevolved.

Can propranolol act as a chemopreventive agent during oral carcinogenesis? An experimental animal study.

The multistep process of oral carcinogenesis provides a biological rationale for the use of chemoprevention in individuals at increased risk of developing oral cancer. We aimed to determine if low doses of propranolol can prevent the development of oral cancer using a tobacco-relevant and p53-associated animal model of cancer initiation. Twenty-six Wistar rats were randomly allocated into two groups, vehicle, and propranolol. All animals received 4-nitroquinoline N-oxide (4NQO) at 25 ppm diluted in the drinking water for 20 weeks. Animals from the propranolol group received propranolol (0.1 mg/kg) 5 days per week by gavage for 18 weeks. The clinical analysis was performed by measuring the area of the lesion and assessment of scores based on lesion appearance (papule; plaque; nodule or ulcerated). Histopathological analysis was performed to determine the presence of epithelial dysplasia or invasive squamous cell carcinoma (SCC). The average lesion area in 4NQO + vehicle and in 4NQO + propranolol groups were 0.20 and 0.28 mm2, respectively (P = 0.53). The percentage of cases clinically graded as papules, thick plaques, nodular areas, and ulcerated lesions was similar between groups (P = 0.94). Histopathological diagnosis also did not differ between groups (P = 0.65), with 54.5 and 70% of cases being diagnosed as SCC in 4NQO and in 4NQO + propranolol groups, respectively. In conclusion, daily doses propranolol at 0.1 mg/kg were not as effective as a chemopreventive therapy in an animal model of 4NQO-induced carcinogenesis.

Suppression of Rat Oral Carcinogenesis by Agonists of Peroxisome Proliferator Activated Receptor γ.

Peroxisome-proliferator-activated receptor γ (PPARγ) is a ligand-activated transcription factor that regulates cell proliferation, differentiation, and apoptosis. In vivo studies were performed to evaluate the activities of two thiazolidinedione PPARγ agonists, rosiglitazone and pioglitazone, as inhibitors of oral carcinogenesis in rats. Oral squamous cell carcinomas (OSCC) were induced in male F344 rats by 4-nitroquinoline-1-oxide (NQO; 20 ppm in the drinking water for 10 weeks). In each study, groups of 30 NQO-treated rats were exposed to a PPARγ agonist beginning at week 10 (one day after completion of NQO administration) or at week 17 (7 weeks post-NQO); chemopreventive agent exposure was continued until study termination at week 22 (rosiglitazone study) or week 24 (pioglitazone study). Administration of rosiglitazone (800 mg/kg diet) beginning at week 10 increased survival, reduced oral cancer incidence, and reduced oral cancer invasion score in comparison to dietary controls; however, chemopreventive activity was largely lost when rosiglitazone administration was delayed until week 17. Administration of pioglitazone (500 mg/kg diet beginning at week 10 or 1000 mg/kg diet beginning at week 17) induced significant reductions in oral cancer incidence without significant effects on OSCC invasion scores. Transcript levels of PPARγ and its three transcriptional variants (PPARγv1, PPARγv2, and PPARγv3) were not significantly different in OSCC versus age- and site-matched phenotypically normal oral tissues from rats treated with NQO. These data suggest that PPARγ provides a useful molecular target for oral cancer chemoprevention, and that overexpression of PPARγ at the transcriptional level in neoplastic lesions is not essential for chemopreventive efficacy.

Chemopreventive and therapeutic modulation of green tea polyphenols on drug metabolizing enzymes in 4-Nitroquinoline 1-oxide induced oral cancer.

Oral cancer is one of the most common cancers in the world. Drugs can modulate the expression of drug metabolizing enzymes and are useful in chemoprevention as well as therapy in cancer. 4-Nitroquinoline 1-oxide (4-NQO) is used to induce oral cancer in the present study. In the present investigation, the effect of green tea polyphenols (GTP) on the activities of cytochrome b5, cytochrome P450, cytochrome b5 reductase (cyt b5 R), cytochrome P450 reductase (cyt P450 R), arryl hydrocarbon hydroxylase (AHH), DT-diaphorase (DTD)(Phase I enzymes) and glutathione-S-transferase (GST) and UDP-glucuronyl transferase (UDP-GT) (Phase II enzymes) were assessed in tongue and oral cavity. In induced rats, there was a decrease in the activity of Phase II enzymes and an increase in the activity of Phase I enzymes. On supplementation of GTP by both simultaneous and post treatment mode (200mg/kg) there was a significant increase in the activity of GST and UDP-GT and a significant decrease in the activity of Phase I enzymes. There was a significant decline in the number of tumors, tumor volume and oral squamous cell carcinoma in both simultaneous and post GTP treated animals relative to 4-NQO induced animals; on comparing simultaneous and post GTP treated animals the number of tumors, tumor volume and oral squamous cell carcinoma was significantly reduced in post treated animals. Thus inhibition of Phase I enzymes could be attributed to the protective efficacy of GTP which deactivates carcinogen and GTP induced the expression of Phase II enzymes that detoxifies the 4-NQO. It can be proposed that GTP plays role as a detoxifying agent by which its modulating role prevented/inhibited the formation of tumor.