Expression of homeobox genes in oral squamous cell carcinoma cell lines treated with all‐trans retinoic acid

Abstract

Oral squamous cell carcinoma (OSCC) may arise from potentially malignant oral lesions. All-trans retinoic acid (atRA), which plays a role in cell growth and differentiation, has been studied as a possible chemotherapeutic agent in the prevention of this progression. While the mechanism by which atRA suppresses cell growth has not been completely elucidated, it is known that homeobox genes are atRA targets. To determine if these genes are involved in the atRA-mediated OSCC growth inhibition, PCR array was performed to evaluate the expression of 84 homeobox genes in atRA-sensitive SCC-25 cells compared to atRA-resistant SCC-9 cells following 7 days with atRA treatment. Results showed that the expression of 8 homeobox genes was downregulated and expression of 4 was upregulated in SCC-25 cells but not in SCC-9 cells. Gene expression levels were confirmed for seven of these genes by RT-qPCR. Expression of three genes that showed threefold downregulation was evaluated in SCC-25 cells treated with atRA for 3, 5, and 7 days. Three different patterns of atRA-dependent gene expression were observed. ALX1 showed downregulation only on day 7. DLX3 showed reduced expression on day 3 and further reduced on day 7. TLX1 showed downregulation only on days 5 and 7. Clearly the expression of homeobox genes is modulated by atRA in OSCC cell lines. However, the time course of this modulation suggests that these genes are not direct targets of atRA mediating OSCC growth suppression. Instead they appear to act as downstream effectors of atRA signaling.

Altered epigenetic regulation of homeobox genes in human oral squamous cell carcinoma cells

“…4(a), Supplementary Table 8 and data not shown). In accord with earlier reports [7,8,56], SCC-9 responses to RA treatment, as assessed by RNAseq, were limited to a small number of transcripts (Supplementary Table 8). PRRX2 and HOXA5 were the only two homeobox transcripts that changed upon RA treatment of SCC-9 cells in our RNAseq experiment (Supplementary Table 8).…”

“…PRRX2 and HOXA5 were the only two homeobox transcripts that changed upon RA treatment of SCC-9 cells in our RNAseq experiment (Supplementary Table 8). Transcripts of homeobox genes in control and RA-treated SCC-9 cells were evaluated by qRT-PCR by an earlier report; among 84 genes included in the assessed panel only two, HOXD12 and MEOX1, exhibited transcript changes of greater than 3-fold upon RA treatment [56]. …”

Identification of putative retinoic acid target genes downstream of mesenchymal Tbx1 during inner ear development

“…This screen identified eighteen genes that have been shown in other systems to be downstream of RA signaling (Figure 1). All genes were altered in the direction of known response to RA, with Adm (Minamino et al, 1995), Cp (Tice et al, 2002), Myt1 (Franco et al, 1999), Ncam1 (De Laurenzi et al, 2000), Pak1 (Csomos et al, 2010), and Vwf (Hatzopoulos et al, 1998) up-regulated and Aplnr (Zhong et al, 2005), Bhmt (Xu et al, 2010), Col2a1 (Jimenez et al, 2001), Clu (Orlandi et al, 2005), Dlx3 (Acquafreda et al, 2010), Fgf4 (Maerz et al, 1998), Hoxc9 (Mao et al, 2011), Itga2b (Liu et al, 2000), Itgb3 (Csomos et al, 2010), Mia1 (Dietz et al, 1996), Msc (Hishikawa et al, 2005), Otor (Roberts et al, 2000), and S100a8 (Liu et al, 2000) down-regulated, consistent with previously published data in vitro or in other model systems (Table 1). …”

“…Expression was lost in the developing semicircular canals (SC) of Mes t -KO embryos, while expression in the endolymphatic duct remained intact (red arrow, Figure 3K). A recent report using an oral squamous cell carcinoma line treated with atRA suggests that Dlx3 is negatively regulated by RA (Acquafreda et al, 2010). …”

“…3K). A recent report using an oral squamous cell carcinoma line treated with atRA suggests that Dlx3 is negatively regulated by RA (Acquafreda et al, 2010).…”