The native fluorescence spectra of retinoic acid (RA)-treated and untreated human breast cancerous cells excited with the selective wavelengths of 300 nm and 340 nm were measured and analyzed using a blind source separation method namely Nonnegative Matrix Factorization (NMF). The results show that the fluorophores of human malignant breast cells change their compositions when they are treated with RA. The reduced contribution from tryptophan, NADH and flavin to the fluorescence of the treated breast cancerous cells was observed in comparison with that of the untreated cells. The results indicate that the decrease of adenosine triphosphate (ATP) in the RA-treated cells. The possible clinical applications of this native fluorescence study are discussed.

Key words: Breast cancer cells; Selective excitation wavelength; Native fluorescence; Tryptophan; Reduced nicotinamide adenine dinucleotide (NADH); Flavin; Nonnegative Matrix Factorization (NMF); Chemo-therapeutic effect; and Retinoic acid.