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

An attempt was made to study whether light-induced fluorescencespectroscopy could be exploited to discriminate premalignantand malignant tissues of hamster buccal pouch carcinogenesisfrom normal tissues during a 16 week regimen of tri-weekly topicalapplication of 7,12- dimethylbenz[a]anthracene (DMBA) in liquidparaffin. Histologically, the DMBA-treated buccal mucosa showedhyperplastic changes at 4–6 weeks, papillomas at 8–10weeks, early invasive carcinomas at 11–13 weeks and finallywell-differentiated squamous cell carcinomas at 14–16weeks of treatment. Acetone extracts of these different stagedtissues with age matched control tissues were excited at 405and 420 nm and the emissions were scanned from 430 and 440 to700 nm respectively. The spectral profiles of control and transformedtissues were found to be different, each displaying their owncharacteristic prominent maxima and other spectral marks. Thespectra of transformed tissues showed characteristic peaks around620–630 nm which did not appear in control tissues andthe fluorescent intensifies at 630 nm [FI(630)nm] were significantlyincreased from early stages onwards when compared to controls.The spectra of DMBA carcinomas developed at the 18th week afterwithdrawal of DMBA application at the 10th week and carcinomaextract spiked with DMBA conlirmed the peak around 620–630could be attributed only to porphyrin compounds accumulatedin transformed tissues. Furthermore, the ratios of FI(520)nm/FI(630)nm of transformed tissues were also significantly decreasedwhen compared to control tissues. This diagnostic test had avery close resemblance with respect to histological studies.These results suggest that this technique using conventionallight-induced fluorescence spectroscopy may be useful for earlydiagnosis of premalignant and malignant lesions of oral cavity.