Abstract: 【Abstract】 Objective To evaluate the inhibitory effect of a retinoid derivative ECPIRM on proliferation of a cutaneous T-cell lymphoma （CTCL） cell line HH, and to explore its potential mechanisms. Methods Cultured HH cells were treated with ECPIRM at different concentrations of 0 （control group）, 5, 10 and 20 μmol/L separately for 72 hours, cell counting kit-8 （CCK8） assay was performed to evaluate the effect of ECPIRM on the proliferative activity of HH cells, and flow cytometry to investigate the effect of ECPIRM on apoptosis of HH cells. Some HH cells were treated with 10 μmol/L ECPIRM for 72 hours, transcriptome sequencing was performed to investigate gene expression changes triggered by ECPIRM in HH cells, and Kyoto encyclopedia of genes and genomes （KEGG） pathway analysis and gene ontology （GO） enrichment analysis were then performed to analyze differentially expressed genes in HH cells induced by ECPIRM. Reverse transcription-qPCR was subsequently conducted to verify changes in key gene expression in related pathways. Intergroup differences were analyzed by using one-way analysis of variance, and least significant difference （LSD）-t test was used for multiple comparisons. Results CCK8 assay showed that the 50% inhibitory concentration （IC50） of ECPIRM on HH cells was 4.91 ± 2.48 μmol/L, the viability of HH cells significantly differed among the control group, and 5-, 10- and 20-μmol/L ECPIRM groups （100.00% ± 2.87%, 49.58% ± 4.53%, 48.36% ± 2.88%, 31.44% ± 2.46%, respectively, F = 162.86, P < 0.001）, and was significantly lower in the 5-, 10- and 20-μmol/L ECPIRM groups than in the control group （t = 15.36, 15.73, 20.89, respectively, all P < 0.001）. Flow cytometry showed that there was a significant difference in the apoptosis rate among the 4 groups （11.51% ± 1.84%, 23.83% ± 5.72%, 36.19% ± 8.33%, 49.75% ± 4.10%, respectively, F = 17.62, P < 0.001）, and the 10- and 20-μmol/L groups showed significantly increased apoptosis rates compared with the control group （t = 4.46, 6.92 respectively, both P < 0.01）. Transcriptomics analysis revealed that the inhibitory effect of ECPIRM on the cellular proliferative activity may be related to the metabolic regulation of steroids. As reverse transcription-qPCR revealed, the 10-μmol/L ECPIRM group showed significantly decreased mRNA expression of L-amino acid oxidase （IL4I1）, acetyl-coenzyme A acetyltransferase 2 （ACAT2）, 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1 （HMGCS1）, mevalonate diphosphate decarboxylase （MVD）, 3-β-hydroxysteroid-8,7-isomerase （EBP）, very low-density lipoprotein receptor （VLDLR）, 3-hydroxy 3-methylglutaryl-CoA reductase （HMGCR） compared with the control group （all P < 0.05）. Conclusion The retinoid derivative ECPIRM exerted marked anti-proliferative and apoptosis-inducing effects on HH cells, which may be related to the decreased expression of key genes involved in steroid metabolism.

Key words: metabolism, Lymphoma, T-cell, cutaneous, Retinoids, Cell proliferation, Apoptosis, HH cells, ECPIRM