Squamous Carcinoma Cell Lines Fail to Respond to 1,25-Dihydroxyvitamin D Despite Normal Levels of the Vitamin D Receptor

Abstract

Squamous carcinoma cells (SCC) fail to differentiate under conditions that are favorable for the growth and differentiation of normal human keratinocytes. Human keratinocytes differentiate from a highly proliferative basal cell to a terminally differentiated cornified cell in culture in the presence of physiological levels of extracellular calcium. 1,25-Dihydroxyvitamin D (1,25[OH]2D3) potentiates this process. Previous studies have shown that the differentiation process in keratinocytes is associated with increased expression of the genes for involucrin and transglutaminase, the products of which participate in cornified envelope formation. The mRNA for involucrin and transglutaminase was not detected in the SCC lines studied (viz. SCC4, 12B2, 12F2, A431, and HACAT) when they were grown in serum free medium. Addition of at least 2% fetal bovine serum for 48 h triggered the expression of these genes, which could then be maintained in the absence of serum. Serum was not required for induction of these genes in keratinocytes. In these cells, 1,25(OH)2D3 stimulated the expression of involucrin and transglutaminase in a concentration-dependent manner, while the SCC lines failed to respond to 1,25(OH)2D3 regardless of whether these cells had been pre-exposed to serum. An important factor that mediates 1,25(OH)2D3-stimulated gene expression is the vitamin D receptor, but vitamin D receptor mRNA levels in all the SCC lines examined were comparable to those in keratinocytes. Furthermore, the vitamin D receptor protein levels in SCC lines as assessed by ligand-binding analysis were comparable to those of keratinocytes. Thus, the mediators of 1,25(OH)2D3 action on gene expression other than the vitamin D receptor may be missing or defective in SCC lines, whereas the mediators of as yet undefined agents in serum may be better expressed in SCC lines than in keratinocytes. Our results indicate that, although SCC lines are capable of expressing the genes for the proteins involved in differentiation, the control of the expression of these genes by 1,25(OH)2D3 is abnormal in SCC despite the presence of a functional vitamin D receptor in concentrations equivalent to those in keratinocytes.

In vitro biocompatibility of poly(vinylidene fluoride–trifluoroethylene)/barium titanate composite using cultures of human periodontal ligament fibroblasts and keratinocytes

“…In addition, it was noticed that the expression of keratin 14 gene remains high on P(VDF-TrFE)/BT even in later periods. This occurs owing to inherent features of SCC cell lines, which maintain the expression of keratins typically expressed by less differentiated keratinocytes [51]. Despite the finding that P(VDFTrFE)/BT supported the expression of typical keratinocyte markers, cell spreading and cell proliferation were impaired under a lower plating density.…”

Altered SMRT levels disrupt vitamin D3 receptor signalling in prostate cancer cells

“…The active metabolite of vitamin D, 1a,25(OH) 2 D 3 , is readily able to initiate gene transactivation and acutely regulate proliferation of normal prostate, breast, and colon epithelial cells and myeloid CD 34-positive precursors (Konety et al, 1996;Ratnam et al, 1996;Tong et al, 1998;Rashid et al, 2001b;Zinser et al, 2002). By contrast, cancer and leukaemic cell lines from these tissues display a spectrum of sensitivities including complete insensitivity to 1a,25(OH) 2 D 3 , irrespective of VDR expression (Munker et al, 1986;Campbell et al, 1997;Kubota et al, 1998;Palmer et al, 2001).…”

Vitamin D and skin cancer: A problem in gene regulation

“…However, the presence of VDR and the ability to produce 1,25(OH) 2 D 3 do not distinguish normal keratinocytes from transformed keratinocytes. All SCC lines that we have tested have both VDR [1] and the ability to produce 1,25(OH) 2 D 3 [11]. More recent studies observed increased 1OHase and VDR expression in the BCC and SCC tumors examined compared with normal epidermis, and increased 25OHase expression in the SCC tumors [2,12].…”

“…Using a model for mammary cancer induction in which medroxyprogesterone pellets are implanted before oral administration of DMBA at ages 5.5 and 7 weeks, Zinser et al [28] found that 85% of VDR-null mice developed tumors (primarily papillomas but some BCCs), whereas none of the wild type mice did. However, transformed keratinocytes are less responsive to the antiproliferative actions of 1,25(OH) 2 D 3 than are normal keratinocytes despite having normal levels of VDR [1,11,15]. One potential mechanism for this resistance proposed by Goltzman et al [29] involves increased serine phosphorylation of the retinoid X receptor ␣ (RXR␣).…”

“…This includes the three major types of skin cancers: basal and squamous cell carcinomas (BCC and SCC) [1,2] and melanomas [3]. These skin cancers are the most common of all malignancies.…”