Functional Characterization of Cultured Cells Derived from an Intraepidermal Carcinoma of the Skin (IEC-1)

Dicker, Tony; Serewko, Magdalena M; Dahler, Alison; Khanna, Kum Kum; Kaur, Pritinder; Li, Amy; Strutton, Geoff; Saunders, Nicholas A.

doi:10.1006/excr.2000.4944

Cited by 17 publications

(28 citation statements)

References 34 publications

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“…SCC cell lines are characterized by deregulated proliferation (accompanied by overexpressed E2F1) and insensitivity to differentiation-inducing agents (Dicker et al, 2000b). If squamous differentiation of keratinocytes is indeed characterized by an increase in the expression ratio of Sp1 to Sp3, we would predict that in SCCs, disruption of this ratio would be observed.…”

Section: Resultsmentioning

confidence: 99%

E2F suppression and Sp1 overexpression are sufficient to induce the differentiation-specific marker, transglutaminase type 1, in a squamous cell carcinoma cell line

et al. 2005

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Recently, E2F function has expanded to include the regulation of differentiation in human epidermal keratinocytes (HEKs). We extend these findings to report that in HEKs, Sp1 is a differentiation-specific activator and a downstream target of E2F-mediated suppression of the differentiation-specific marker, transglutaminase type 1 (TG-1). Deletion of elements between À0.084 to À0.034 kb of the TG-1 promoter disabled E2F1-induced suppression of promoter activity. Electrophoretic mobility shift assays (EMSAs) demonstrated that Sp1 and Sp3 bound this region. Protein expression analysis suggested that squamous differentiation was accompanied by increased Sp1/Sp3 ratio. Cotransfection of proliferating HEKs or the squamous cell carcinoma (SCC) cell line, KJD-1/SV40, with an E2F inhibitor (E2Fd/n) and Sp1 expression plasmid was sufficient to activate the TG-1 promoter. The suppression of Sp1 activity by E2F in differentiated cells appeared to be indirect since we found no evidence of an Sp1/E2F coassociation on the TG-1 promoter fragment. Moreover, E2F inhibition in the presence of a differentiation stimulus induced Sp1 protein. These data demonstrate that (i) Sp1 can act as a differentiation stimulus, (ii) E2F-mediated suppression of differentiation-specific markers is indirect via Sp1 inhibition and (iii) a combination of E2F inhibition and Sp1 activation could form the basis of a differentiation therapy for SCCs.

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Section: Resultsmentioning

confidence: 99%

E2F suppression and Sp1 overexpression are sufficient to induce the differentiation-specific marker, transglutaminase type 1, in a squamous cell carcinoma cell line

et al. 2005

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“…Growth arrest and differentiation was induced by maintaining confluent cells in culture over 48 h or by treatment with the protein kinase C (PKC) activator, 12-O-tetradecanoyl-phorbol-13-acetate (TPA, 50 ng/ml for 16 -48 h). Both these treatment regimes induce robust and reproducible differentiation in HEKs but not in SCC cell lines (10,(41)(42)(43).…”

Section: Methodsmentioning

confidence: 99%

E2F Modulates Keratinocyte Squamous Differentiation

Wong

Barnes

Dahler

et al. 2003

Journal of Biological Chemistry

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E2F regulation is essential for normal cell cycle progression. Therefore, it is not surprising that squamous cell carcinoma cell lines (SCC) overexpress E2F1 and exhibit deregulated E2F activity when compared with normal keratinocytes. Indeed, deliberate E2F1 deregulation has been shown to induce hyperplasia and skin tumor formation. In this study, we report on a dual role for E2F as a mediator of keratinocyte proliferation and modulator of squamous differentiation. Overexpression of E2F isoforms in confluent primary keratinocyte cultures resulted in suppression of differentiation-associated markers. Moreover, we found that the DNA binding domain and the trans-activation domain of E2F1 are important in mediating suppression of differentiation. Use of a dominant/negative form of E2F1 (E2F d/n) found that E2F inhibition alone is sufficient to suppress the activity of proliferation-associated markers but is not capable of inducing differentiation markers. However, if the E2F d/n is expressed in differentiated keratinocytes, differentiation marker activity is further induced, suggesting that E2F may act as a modulator of squamous differentiation. We therefore examined the effects of E2F d/n in a differentiation-insensitive SCC cell line. We found that treatment with the differentiating agent, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), or expression of E2F d/n alone had no effect on differentiation markers. However, a combination of E2F d/n ؉ TPA induced the expression of differentiation markers. Combined, these data indicate that E2F may play a key role in keratinocyte differentiation. These data also illustrate the unique potential of anti-E2F therapies in arresting proliferation and inducing differentiation of SCCs.

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“…Known numbers of cells were placed into 6-well plates and allowed to grow for 14 days, following which plates were fixed and stained with Coomassie Blue (21) and counted. Colony forming efficiency (CFE) was expressed as the total number of colonies/total number of cells plated Â 100.…”

Section: Colony Forming Assaymentioning

confidence: 99%

“…Dysregulation of squamous differentiation is fundamental to the development of SCC and has been reported to occur early in premalignant lesions (21). In particular, there have been several recent studies that report an association between PRC2-mediated regulation of gene expression and head and neck squamous cell carcinoma (HNSCC).…”

Section: Introductionmentioning

confidence: 99%

Dysregulation of the Repressive H3K27 Trimethylation Mark in Head and Neck Squamous Cell Carcinoma Contributes to Dysregulated Squamous Differentiation

Gannon

Long

Endo‐Munoz

et al. 2013

Clinical Cancer Research

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Purpose: Head and neck squamous cell carcinoma (HNSCC) is one of the most prevalent cancers diagnosed worldwide and is associated with a 5-year survival rate of 55%. EZH2, a component of the polycomb repressor complex 2, trimethylates H3K27 (H3K27me3), which has been shown to drive squamous differentiation in normal keratinocytes. This study determined whether inhibition of EZH2-mediated epigenetic silencing could induce differentiation or provide therapeutic benefit in HNSCC.Experimental Design: We determined the effects of inhibiting EZH2, by either RNA interference or pharmacologically, on HNSCC growth, viability, and differentiation in vitro. Xenografts of HNSCC cell lines were used to assess efficacy of 3-deazaneplanocin A (DZNep), an inhibitor of H3K27 trimethylation, in vivo.Results: EZH2 was highly expressed in HNSCC cell lines in vitro and tissue microarray analysis revealed high expression in (n ¼ 59) in situ relative to normal oral epithelium (n ¼ 12). Inhibition of EZH2 with siRNA could induce expression of differentiation genes in differentiation-refractory squamous cell carcinoma cell lines. Differentiation-refractory HNSCC cell lines displayed persistent H3K27me3 on the promoters of differentiation genes. DZNep caused cancer-cell-specific apoptosis in addition to a profound reduction in colony-forming efficiency and induction of some squamous differentiation genes. Furthermore, in vivo, DZNep attenuated tumor growth in two different xenograft models, caused intratumor inhibition of EZH2, and induction of differentiation genes in situ.Conclusions: Collectively, these data suggest that aberrant differentiation in HNSCC may be attributed to epigenetic dysregulation and suggest that inhibition of PRC2-mediated gene repression may represent a potential therapeutic target.

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Functional Characterization of Cultured Cells Derived from an Intraepidermal Carcinoma of the Skin (IEC-1)

Cited by 17 publications

References 34 publications

E2F suppression and Sp1 overexpression are sufficient to induce the differentiation-specific marker, transglutaminase type 1, in a squamous cell carcinoma cell line

E2F suppression and Sp1 overexpression are sufficient to induce the differentiation-specific marker, transglutaminase type 1, in a squamous cell carcinoma cell line

E2F Modulates Keratinocyte Squamous Differentiation

Dysregulation of the Repressive H3K27 Trimethylation Mark in Head and Neck Squamous Cell Carcinoma Contributes to Dysregulated Squamous Differentiation

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