Fluorescence spectroscopic identification of 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis.

An attempt was made to study whether light-induced fluorescence spectroscopy could be exploited to discriminate premalignant and malignant tissues of hamster buccal pouch carcinogenesis from normal tissues during a 16 week regimen of tri-weekly topical application of 7,12-dimethylbenz[a]anthracene (DMBA) in liquid paraffin. Histologically, the DMBA-treated buccal mucosa showed hyperplastic changes at 4-6 weeks, papillomas at 8-10 weeks, early invasive carcinomas at 11-13 weeks and finally well-differentiated squamous cell carcinomas at 14-16 weeks of treatment. Acetone extracts of these different staged tissues with age matched control tissues were excited at 405 and 420 nm and the emissions were scanned from 430 and 440 to 700 nm respectively. The spectral profiles of control and transformed tissues were found to be different, each displaying their own characteristic prominent maxima and other spectral marks. The spectra of transformed tissues showed characteristic peaks around 620-630 nm which did not appear in control tissues and the fluorescent intensities at 630 nm [FI(630)nm] were significantly increased from early stages onwards when compared to controls. The spectra of DMBA carcinomas developed at the 18th week after withdrawal of DMBA application at the 10th week and carcinoma extract spiked with DMBA confirmed the peak around 620-630 could be attributed only to porphyrin compounds accumulated in transformed tissues. Furthermore, the ratios of FI(520)nm/FI(630)nm of transformed tissues were also significantly decreased when compared to control tissues. This diagnostic test had a very close resemblance with respect to histological studies. These results suggest that this technique using conventional light-induced fluorescence spectroscopy may be useful for early diagnosis of premalignant and malignant lesions of oral cavity.