Response of Aldehyde Dehydrogenase (ALDH) after Cisplatin and All-Trans Retinoic Acid (ATRA) treatment of Spheroid-derived Cells (SDCs) from cervical cancer cell lines

Background:

Cancer stem cells (CSC) can be enriched by 3- dimensional culture techniques (Spheroids). ALDH is regarded a ubiquitous CSC marker. It contributes to cancer drug resistance due to its detoxificating property. ATRA is a downstream product of ALDH and is capable to induce CSC differentiation. We observed the impact of ATRA or/and cisplatin on ALDH expression in cervical cancer cell line-derived SDCs.

Materials and methods:

Cell lines, Hela, MRIH186, and SiHa were used to generate spheroids and subsequently treated with different concentrations of ATRA or/and cisplatin. ALDH expression was evaluated after 72h drug administration using ALDEFLUOR kit by flow cytometry. The mRNA expression of ALDH isotypes was detected by real time PCR.

Results:

Compared to the corresponding monolayer cells, the spheroid-derived cells showed higher ALDH+ cell frequency (5.12-, 1.89-, 1.85-fold up-regulated Hela, MRIH186, and SiHa, respectively; p < 0.05). Upon treatment with different concentrations of ATRA, the ALDH+ cell proportion showed a dose-dependent reduction in all cell lines. A bi-phasic response was found after cisplatin treatment. At concentrations below its IC₅₀, cisplatin increased ALDH+ frequency (1.83-, 1.67-, 2.04-fold in Hela, MRIH186, and SiHa, respectively; p < 0.05). At higher cisplatin concentration ALDH+ cell frequency was sharply reduced. Combined treatment with ATRA and cisplatin resulted in an enhanced decline of ALDH expression. mRNA expression of ALDH1A1 and ALDH1A3 was reduced by ATRA.

Conclusions:

ATRA can reduce ALDH+ cell frequency in cervical SDCs. The combination of ATRA with cytotoxic drugs might be a promising strategy to overcome the chemo-resistance caused by CSC.