Distinct patterns of all‐trans retinoic acid dependent expression of HOXB and HOXC homeogenes in human embryonal and small‐cell lung carcinoma cell lines

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Abstract
The expression patterns of the class I homeogenes HOXB and HOXC clusters in the presence of retinoic acid (RA) were studied in two human small‐cell lung cancer (SCLC) cell lines and compared to that of NT2/D1 embryonal carcinoma cells. Contrasting with the sequential 3′‐5′ induction of the HOX genes observed after RA treatment of embryonic NT2/D1 cells, in the SCLC cells the responding genes (induced or down‐regulated) were interspersed with insensitive genes (expressed or unexpressed), while no genomic alteration affected the corresponding clusters. These findings imply that HOX gene regulatory mechanisms are altered in non‐embryonic SCLC cells, perhaps reflecting their ability to respond to more diversified stimuli, in relation with their origin from adult tissues.