Induction Of Squamous Cell Carcinoma Research Articles

Abstract 98: The role of HORMAD1 in transformation of keratinocytes following vemurafenib treatment

Abstract BRAF inhibitor (BRAFi) therapies are highly effective treatments for metastatic melanoma. However, BRAFi monotherapies are associated with a significant risk of squamous cell carcinoma (SCC) development in melanoma patients. Consequently, BRAF inhibition results in an unanticipated activation of the MAPK pathway in surrounding cells that harbour wildtype BRAF. Fortunately, a combination approach with both a BRAFi and the selective MAPK inhibitor (MEKi), trametinib, attenuates BRAFi-induced risk of SCCs. Despite the fact that this combination therapy is widely used in clinical practice, the mechanisms associated with SCC induction and why this effect is attenuated with a MEK inhibitor remain poorly understood. HORMAD1, a meiosis specific gene, has been shown to have an impact on genomic instability and proliferation in the development of SCCs. Moreover, recent work in our lab has demonstrated that the MAPK pathway regulates HORMAD1 expression in SCC cell lines. Therefore, we sought to investigate a potential role of HORMAD1 in the risk and development of SCCs as a mechanism of BRAFi that is attenuated with the co-administration of the MEKi, trametinib. Using the BRAFi, vemurafenib, we inhibited the kinase activity of activated BRAF (V600E) and the MEKi, trametinib to evaluate the expression of HORMAD1 in melanoma and normal keratinocyte cell lines. To determine the effects of these two inhibitors, a cell proliferation assay was conducted followed by the evaluation of various components of cell cycle regulation and genomic instability. We found that HORMAD1 protein expression levels increased following treatment with the BRAFi, vemurafenib, in the normal keratinocyte cell line, HaCaT, but not in the melanoma cell line, A375. In contrast, HORMAD1 expression decreased following treatment with the MEKi, trametinib in both HaCaT and A375. Cell proliferation assays depict a vulnerability to both vemurafenib and trametinib in both normal and melanoma cell lines, however, HaCaT cells appear to be more susceptible to increased levels of genomic instability following treatment with vemurafenib when compared to A375. Our results suggest that HORMAD1 likely plays a key role in the development of SCCs by increasing genomic instability and proliferation in normal keratinocytes following BRAFi monotreatment. The increased risk of SCC formation is attenuated by dampening HORMAD1 levels with the co-administration of the MEKi, trametinib. Citation Format: Jennifer Gantchev, Amelia Martinez Villarreal, Brandon Ramchatesingh, Ivan V. Litvinov. The role of HORMAD1 in transformation of keratinocytes following vemurafenib treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 98.

286 HORMAD1 Contributes to the Development of Squamous Cell Carcinomas in Melanoma Patients

BRAF inhibitor (BRAFi) therapies are effective treatments for metastatic melanoma. However, BRAFi monotherapies are associated with a significant risk of squamous cell carcinoma (SCC) in melanoma patients. Consequently, BRAF inhibition results in an activation of the MAPK pathway in cells that harbour wildtype BRAF. Fortunately, a combination approach with both a BRAFi and the selective MAPK inhibitor (MEKi), trametinib, attenuates BRAFi-induced risk of SCCs. Despite the wide use of this therapy, the mechanisms associated with SCC induction remain poorly understood. HORMAD1, a meiosis gene, has been shown to have an impact on genomic instability and proliferation in the development of SCCs. Recent work has shown that HORMAD1 expression is regulated by the MAPK pathway in SCC cell lines. Therefore, we sought to investigate a potential role of HORMAD1 in the risk and development of SCCs that is attenuated with the administration of the MEKi, trametinib. We used BRAFi, vemurafenib and the MEKi, trametinib to evaluate the expression of HORMAD1 in melanoma and normal keratinocyte cell lines. To determine the effects of the two inhibitors, a cell proliferation assay was conducted followed by the evaluation of various components of cell cycle regulation and genomic instability. We found that HORMAD1 protein expression increased following treatment with vemurafenib in normal keratinocytes but not in a melanoma cells. In contrast, HORMAD1 expression decreased following treatment with trametinib in both HaCaT and A375. Cell proliferation assays depict a vulnerability to both vemurafenib and trametinib in both normal and melanoma cell lines, however, HaCaT cells appear to be more susceptible to increased levels of genomic instability following treatment with vemurafenib. Our results suggest that HORMAD1 likely plays a key role in the development of SCCs by increasing genomic instability and proliferation in normal keratinocytes following BRAFi monotreatment. The increased risk of SCC formation is attenuated by dampening HORMAD1 levels with the co-administration of the MEKi, trametinib.

Induction of squamous cell carcinoma after MAP3K8 overexpression in murine salivry gland epithelial cells.

Salivary gland neoplasms are relatively rare and comprise only 1%-4% of all human neoplasms. Salivary gland neoplasms also show an extremely wide range of morphological diversity. Currently, the genetic alterations and corresponding molecular mechanisms underlying salivary gland neoplasms development remain largely unknown. We generated an inducible Tet-MAP3K8::MMTV-rTA mouse model by crossing the MAP3K8 transgenic mice with MMTR-rTA transgenic mice to express MAP3K8 in the salivary gland. MAP3K8 overexpression in the murine salivary glands of Tet-MAP3K8::MMTR-rTA transgenic mice induces tumorigenesis. Pathological investigations reveal partial fibrosis and adenosis of salivary glands, and foci of atypical squamoid cellular proliferation, which represent invasive squamous cell carcinoma (SCC). MAP3K8 overexpression is associated with SCC development in murine salivary glands. It provides an in vivo framework for the understanding of molecular mechanisms underlying SCC development in the salivary glands and also for the development of a future therapeutic strategy targeting this tumor type.

Re-Examination of the Esophageal Squamous Cell Carcinoma Model in Rats Induced by N-Nitrososarcosine Ethyl Ester Precursors.

Studies of the molecular mechanisms of esophageal cancer development have to be carried out on sufficient amount of tumor material, obtained under conditions of controlled exposure to carcinogenic factors. Esophageal cancer models on laboratory animals serve an indispensable source of this material. One of these models is esophageal cancer induction in rats by N-nitroso compound precursors. Despite adequate reproduction of human esophageal cancer, this model in fact has not been used since the 1990ies. Re-examination of esophageal cancer model, induced by N-nitrososarcosine ethyl ester precursors, is carried out and its efficiency in induction of squamous cell carcinoma is confirmed.

Predicted increased risk of squamous cell carcinoma induction associated with sunbed exposure habits.

Solar ultraviolet radiation (UVR) is recognized as the principal environmental cause of skin cancer. In particular, the risk of induction of squamous cell carcinoma (SCC) has been shown to increase with cumulative exposure to UVR. Models of risk of SCC induction have been developed but these do not include the use of sunbeds. To explore the links between sunbed exposure and risk of SCC induction. To this end, the values of published on-site UVR levels emitted from sunbeds were used to provide real measured sunbed exposure levels to inform the model. The model incorporated three conditions of exposure: day-to-day, holiday and sunbed exposure. The risks associated with different exposure scenarios were implemented in the model. Baseline exposure comprised day-to-day and holiday exposure. Relative risk (RR) was defined as the risk of SCC induction from (sunbed + baseline dose)/baseline dose. The RR of SCC induction from estimated median sunbed exposure output [176 standard erythemal dose (SED) per year; 20-35 years of age] in addition to median baseline sun exposure level (166 SED year + 85.5 SED per year holiday) was 1.9 (90% risk increase) up to 55 years of age. A higher sunbed exposure (302 SED per year; 20-35 years of age) produced an RR value of 2.8 (180% increase) at 55 years of age. This is the first time that a risk model for SCC of the skin has been developed that includes estimated sunbed doses derived from measured irradiance data. The model demonstrates that the additional risk associated with sunbed use may be significant, particularly when high-output, fast-tan sunbeds are used.

Topically Applied Hsp90 Inhibitor 17AAG Inhibits UVR-Induced Cutaneous Squamous Cell Carcinomas

We present here that Heat shock protein 90 (Hsp90) inhibitor 17-(allylamino)-17-demethoxygeldanamycin (17AAG), when topically applied to mouse skin, inhibits ultraviolet radiation (UVR)-induced development of cutaneous squamous cell carcinoma (SCC). In these experiments, DMSO:acetone (1:40 v/v) solution of 17AAG (500nmol) was applied topically to mouse skin in conjunction with each UVR exposure (1.8 kJ/m2). The UVR source was Kodacel-filtered FS-40 sun lamps (approximately 60% UVB and 40% UVA). In independent experiments with three separate mouse lines (SKH-1 hairless mice, wild-type FVB, and PKCε overexpressing transgenic FVB mice), 17AAG treatment increased the latency and decreased both the incidence and multiplicity of UVR-induced SCC. Topical 17AAG alone or in conjunction with UVR treatments elicited neither skin nor systemic toxicity. 17AAG-caused inhibition of SCC induction was accompanied by decrease in UVR-induced: 1) hyperplasia, 2) Hsp90β-PKCε interaction, 3) expression levels of Hsp90β, Stat3, pStat3Ser727, pStat3Tyr705, pAktSer473 and matrix metalloproteinase (MMPs). The results presented here indicate that topical Hsp90 inhibitor 17AAG is effective in prevention of UVR-induced epidermal hyperplasia and SCC. One may conclude from the preclinical data presented here that topical 17AAG may be useful for prevention of UVR-induced inflammation and cutaneous SCC either developed in UVR exposed or organ transplant population.

Neonatal mice do not have increased sensitivity to induction of squamous cell carcinomas

Squamous cell carcinoma (SCC) is linked with the lifelong cumulative effect of ultraviolet radiation (UVR). In contrast, epidemiological data have shown that sunburn in childhood is a stronger risk factor for cutaneous malignant melanoma than continuous UVR, indicating a higher carcinogenic sensitivity early in life. We investigated how a high neonatal dose of UVR affects the development of SCC in mice irradiated later in life. We used simulated solar radiation (sun) and solarium radiation (solarium). Ninety-nine C3.Cg/TifBomTac-immunocompetent hairless mice received 0, 25 or 35 standard erythema doses (SED) UVR when they were 4 days old followed by 4 SED sun or 4 SED solarium three times/weekly from 9 weeks of age. Tumours developed faster in mice treated with 35 SED UVR + 4 SED sun compared with 4 SED sun, but no change was observed in the cumulative dose required to achieve tumours. Tumours also developed faster in mice treated with 35 SED UVR + 4 SED solarium compared with 4 SED solarium, and a difference was also observed in the cumulative dose required to achieve tumours. If the Skin Cancer Utrecht-Philadelphia-murine spectrum was used to weigh the delivered irradiance instead of the International Commission on Illumination erythema action spectrum, tumours developed after the same accumulated dose. In conclusion, this study does not indicate increased sensitivity to induction of SCC early in life.

Effects of heme oxygenase-1 on induction and development of chemically induced squamous cell carcinoma in mice

Heme oxygenase-1 (HO-1) is an antioxidative and cytoprotective enzyme, which may protect neoplastic cells against anticancer therapies, thereby promoting the progression of growing tumors. Our aim was to investigate the role of HO-1 in cancer induction. Experiments were performed in HO-1+/+, HO-1+/−, and HO-1−/− mice subjected to chemical induction of squamous cell carcinoma with 7,12-dimethylbenz[a]anthracene and phorbol 12-myristate 13-acetate. Measurements of cytoprotective genes in the livers evidenced systemic oxidative stress in the mice of all the HO-1 genotypes. Carcinogen-induced lesions appeared earlier in HO-1−/− and HO-1+/− than in wild-type animals. They also contained much higher concentrations of vascular endothelial growth factor and keratinocyte chemoattractant, but lower levels of tumor necrosis factor-α and interleukin-12. Furthermore, tumors grew much larger in HO-1 knockouts than in the other groups, which was accompanied by an increased rate of animal mortality. However, pathomorphological analysis indicated that HO-1−/− lesions were mainly large but benign papillomas. In contrast, in mice expressing HO-1, most lesions displayed dysplastic features and developed to invasive carcinoma. Thus, HO-1 may protect healthy tissues against carcinogen-induced injury, but in already growing tumors it seems to favor their progression toward more malignant forms.

Induction of human squamous cell-type carcinomas by arsenic.

Arsenic is a potent human carcinogen. Around one hundred million people worldwide have potentially been exposed to this metalloid at concentrations considered unsafe. Exposure occurs generally through drinking water from natural geological sources, making it difficult to control this contamination. Arsenic biotransformation is suspected to have a role in arsenic-related health effects ranging from acute toxicities to development of malignancies associated with chronic exposure. It has been demonstrated that arsenic exhibits preference for induction of squamous cell carcinomas in the human, especially skin and lung cancer. Interestingly, keratins emerge as a relevant factor in this arsenic-related squamous cell-type preference. Additionally, both genomic and epigenomic alterations have been associated with arsenic-driven neoplastic process. Some of these aberrations, as well as changes in other factors such as keratins, could explain the association between arsenic and squamous cell carcinomas in humans.

Abstract 1881: Plumbagin, a medicinal plant-derived naphthoquinone, inhibits ultraviolet radiation-induced cutaneous damage and development of squamous cell carcinomas

Abstract Plumbagin (PL) (5-hydroxy-2-methyl-1,4-napthoquinone), a medicinal plant-derived naphthoquinone, was isolated from the roots of the Plumbago zeylanica L. (also known as Chitrak;). The roots of Plumbago zeylanica have been used in Indian medicine for more than 2,500 years for treatments of various ailments. PL is also present in black walnut and other various medicinal plants. In Ayurveda, this herb is considered one of the most potent medicines used for various skin ailments, like leucoderma, psoriasis, leprosy, and scabies. We present here that topical application of non-toxic doses (100-500 nmoles) of PL to skin elicits dose-dependent inhibition of ultraviolet radiation (UVR)-induced cutaneous damage and development of squamous cell carcinomas (SCC). In this experiment, FVB/N mice were exposed to UVR (2 kJ/m2) three times weekly from a bank of six kodacel-filtered FS40 sunlamps (approximately 60% UVB and 40% UVA). The vehicle acetone or the indicated doses of PL in 0.2 ml acetone were applied to the dorsal skin 15 min after UVR exposure. Carcinoma incidence in mice treated with vehicle, 100, 200 or 500 nmoles PL, at 44 weeks post UVR, were 86%, 80% (p=0.67), 53% (p=0.06) and 7% (p=0.0025), respectively. Both vehicle and PL treated mice gained weight and did not exhibit any sign of toxicity during the entire period of the experiment. The molecular mechanisms associated with inhibition of UVR-induced development of SCC involved both induction of apoptosis and inhibition of cell proliferation. Specific findings are that PL treatment increased UVR-induced expression of fas-associated death domain (FADD) protein, Bax, p21, p27 and PARP cleavage. PL treatment also inhibited cell survival by decreasing the expression of pERK1/2, p85 PI3K, pAKT(ser473), Bcl2, and BclXL. Plumbagin also inhibited constitutive activation of transcription factors Stat3, NF-kB and AP-1. In summary, PL has been shown to exert both anticancer and antiproliferative activities in animal models as well as in cell culture. For example, PL, fed in the diet (200 ppm), significantly inhibits azoxymethane-induced intestinal tumors in rat. PL has chemotherapeutic potential as an anti-cancer agent. PL inhibits ectopic growth of breast cancer cells MDA-MB-231, nonsmall cell lung cancer cells A549, melanoma A375-52 cells and prostate cancer DU145 cells in nude mice (J Biol Chem 2006,281:17023, Cancer Res. 2008, 68:9024). We have now shown that PL inhibits the induction of SCC elicited by UVR, the most ubiquitous environmental carcinogen. Taken together, we conclude that PL may be explored as a naturally occurring agent in the prevention and treatment of human cancers (Support: NIH grants CA102431, CA35368 and T32ES007015) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1881.

Abstract 1591: Protein kinase Cε, which is linked to ultraviolet radiation-induced cutaneous damage and development of squamous cell carcinomas, associates with Hsp90β, a core component of multiprotein complex inolving several collaborating chaperones Hsp70/Hsp40, Hop/sti, Cdc37 and p21

Abstract Chronic exposure to ultraviolet radiation (UVR) is the most common etiologic factor linked to the development of squamous cell carcinoma (SCC), a nonmelanoma form of skin cancer that can metastasize. We have reported that protein kinase C epsilon (PKCε) expression level dictates the susceptibility of mice to the development of SCC by UVR. As compared to wildtype littermates, PKCε over-expressing transgenic mice exhibit decreases in tumor latency by 12 weeks and a 3-fold increase in tumor multiplicity (Cancer Research, 64, 7756, 2004). To find clues about the mechanism by which PKCε may impart susceptibility to UVR-induced development of SCC, we found that PKCε interacts with heat shock protein (Hsp) 90β. Hsp90 is a ubiquitous molecular chaperone, which plays key roles in the folding, activation and assembly of a range of structurally and functionally different client proteins (e.g., telomerase, nuclear hormone receptors, protein kinases) in eukaryotic cells. Hsp90, a core component of multiprotein complex involving several collaborating chaperons (e.g., Hsp70/Hsp40, Hop/sti1, Cdc37, p21), exhibits a high degree of specificity towards client proteins. In the present experiments, mice were exposed to a single UVR (2 kJ/m2) treatment, emitted by Kodacel-filtered FS-40 sun lamps (approximately 60% UVB and 40% UVA). In reciprocal immunoprecipitation/blotting experiments, Hsp90β and its associated chaperons Hsp70 and p21 co-immunoprecipitated with PKCε in intact mouse epidermis in vivo. The association of PKCε with Hsp90β was further enhanced after UVR exposure of dorsal skin in both PKCε transgenic and wild-type mice. The association of PKCε with Hsp90β was significantly increased in PKCε over-expressing transgenic mice as compared to wild-type littermates. In summary, association of Hsp90 with its client PKC is essential for both its maturation into a signaling-competent enzyme and enzyme stability (JBC, 284: 4921, 2008). In UVR mouse skin carcinogenesis, association of Hsp90β with PKCε may be required for sustained PKCε activity. We have previously reported that PKCε interacts with Stat3, phosphorylates Stat3Ser727 and is essential for Stat3-regulated gene expression (Cancer Research, 67, 1385, 2007). PKCε overexpressing transgenic mice exhibits constitutive activation of Stat3 and increased susceptibility to SCC induction by UVR. Association of Hsp90 with PKCε may critical for these biological effects. We conclude that Hsp90, PKCε and Stat3 are potential molecular targets for human cancer prevention and treatment (Support: NIH grants CA102431, CA35368 and T32ES007015) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1591.

Protein kinase Cɛ mediates Stat3Ser727 phosphorylation, Stat3-regulated gene expression, and cell invasion in various human cancer cell lines through integration with MAPK cascade (RAF-1, MEK1/2, and ERK1/2)

Protein kinase C epsilon (PKCε), a novel calcium-independent PKC isoform, has been shown to be a transforming oncogene. PKCε-mediated oncogenic activity is linked to its ability to promote cell survival. However, the mechanisms by which PKCε signals cell survival remain elusive. We found that signal transducers and activators of transcription 3 (Stat3), which is constitutively activated in a wide variety of human cancers, is a protein partner of PKCε. Stat3 has two conserved amino acid (Tyr705 and Ser727) residues, which are phosphorylated during Stat3 activation. PKCε interacts with Stat3α isoform which has Ser727 and not with Stat3β isoform which lacks Ser727. PKCε-Stat3 interaction and Stat3Ser727 phosphorylation was initially observed during induction of squamous cell carcinomas and in prostate cancer. Now we present that: 1) PKCε physically interacts with Stat3α isoform in various human cancer cells: skin melanomas (MeWo and WM266-4), gliomas (T98G and MO59K), bladder (RT-4 and UM-UC-3), colon (Caco-2), lung (H1650), pancreatic (PANC-1), and breast (MCF-7 and MDA:MB-231). 2) Inhibition of PKCε expression using specific siRNA inhibits Stat3Ser727 phosphorylation, Stat3-DNA binding, Stat3-regulated gene expression as well as cell invasion. 3) PKCε mediates Stat3Ser727 phosphorylation via integration with the MAPK cascade (RAF-1, MEK1/2, and ERK1/2). The results indicate that PKCε-mediated Stat3Ser727 phosphorylation is essential for constitutive activation of Stat3 and cell invasion in various human cancers.

Abstract PL05-03: Future challenges of targeted therapy

Abstract PL05-03: Future challenges of targeted therapy

Re: Modulation of basal and squamous cell carcinoma by endogenous estrogen in mouse models of skin cancer

Patched1 heterozygous mice (Ptch1(+/-)) are useful for basal cell carcinoma (BCC) studies, being remarkably susceptible to BCC induction by ultraviolet or ionizing radiation. Analogously, skin carcinogenesis-susceptible (Car-S) mice are elective for studies of papilloma and squamous cell carcinoma (SCC) induction. We previously reported a striking effect of gender on BCC induction in Ptch1(+/-) mice, with total resistance of females; likewise, Car-S females show increased skin tumor resistance relative to males. Here, we investigated the protective role of endogenous estrogen in skin keratinocyte tumorigenesis. Control (CN) and ovariectomized Ptch1(+/-) or Car-S females were irradiated for BCC induction or topically treated with chemical carcinogens for SCC induction. Susceptibility to BCC or SCC was dramatically increased in ovariectomized Ptch1(+/-) and Car-S females and restored to levels observed in males. Remarkably, progression of initially benign papillomas to malignant SCC occurred only in ovariectomized Car-S females. We explored the mechanisms underlying tumor progression and report overexpression of estrogen receptor (ER)-alpha, downregulation of ERbeta and upregulation of cyclin D1 in papillomas from ovariectomized Car-S relative to papillomas from CN females. Thus, an imbalanced ERalpha/ERbeta expression may be associated with estrogen-mediated modulation of non-melanoma skin carcinogenesis, with a key role played by cyclin D1. Our findings underscore a highly protective role of endogenous estrogen against skin tumorigenesis by diverse agents in two independent mouse models of skin cancer.

Modulation of basal and squamous cell carcinoma by endogenous estrogen in mouse models of skin cancer

Patched1 heterozygous mice (Ptch1(+/-)) are useful for basal cell carcinoma (BCC) studies, being remarkably susceptible to BCC induction by ultraviolet or ionizing radiation. Analogously, skin carcinogenesis-susceptible (Car-S) mice are elective for studies of papilloma and squamous cell carcinoma (SCC) induction. We previously reported a striking effect of gender on BCC induction in Ptch1(+/-) mice, with total resistance of females; likewise, Car-S females show increased skin tumor resistance relative to males. Here, we investigated the protective role of endogenous estrogen in skin keratinocyte tumorigenesis. Control (CN) and ovariectomized Ptch1(+/-) or Car-S females were irradiated for BCC induction or topically treated with chemical carcinogens for SCC induction. Susceptibility to BCC or SCC was dramatically increased in ovariectomized Ptch1(+/-) and Car-S females and restored to levels observed in males. Remarkably, progression of initially benign papillomas to malignant SCC occurred only in ovariectomized Car-S females. We explored the mechanisms underlying tumor progression and report overexpression of estrogen receptor (ER)-alpha, downregulation of ERbeta and upregulation of cyclin D1 in papillomas from ovariectomized Car-S relative to papillomas from CN females. Thus, an imbalanced ERalpha/ERbeta expression may be associated with estrogen-mediated modulation of non-melanoma skin carcinogenesis, with a key role played by cyclin D1. Our findings underscore a highly protective role of endogenous estrogen against skin tumorigenesis by diverse agents in two independent mouse models of skin cancer.

Early Events in UV Carcinogenesis—DNA Damage, Target Cells and Mutant p53 Foci†

Skin carcinomas are the most common cancers in fair-skinned populations of North West European descent. The risk is closely related to sun (UV) exposure and susceptibility to sunburn. Induction of squamous cell carcinomas (SCCs) in the skin of hairless mice by daily UVB exposure appears to emulate the genesis of these tumors in humans quite well. The carcinomas, and the UVB signature mutations that they carry in their p53 genes, can be linked most specifically to the induction of cyclobutane pyrimidine dimers (CPDs). The wavelength dependence of the induction of carcinomas parallels that of CPD induction over the UVB and UVA2 spectral regions. Microscopic clusters of cells overexpressing p53 with UVB signature mutations ("p53 patches") can be detected in the interfollicular epidermis long before the skin tumors arise. DNA repair--more precisely nucleotide excision repair--is a crucial line of defense against UV-induced p53 patches and skin carcinomas. Although chemoprevention of UV carcinogenesis, e.g. with difluoromethylornithine, may be successful by inhibiting the outgrowth of tumors, it may be better to counter the initial steps in tumor development. As the p53 patches appear to be potential precursors of SCCs, regression of p53 patches in unexposed skin should lower subsequent development of SCCs. However, "holoclonal" p53 patches might persist. Ablation of the interfollicular epidermis would be expected to abrogate development of SCC, and negation of this expectation [Faurschou A. et al., Exp. Dermatol. 2007;16:485-489] would indicate that SCCs stem from deep-seated cells in the hair follicles. Careful examination of archival material showed that although most small p53 patches arise interfollicularly, some may actually arise high up in a follicle, in the infundibulum.

The role of reactive oxygen species in apoptosis induction of squamous cell carcinoma

The role of reactive oxygen species in apoptosis induction of squamous cell carcinoma

Induction of squamous cell carcinoma of forestomach in diabetic rats by single alloxan treatment

Male rats of WBN/Kob strain are one of the diabetic model animals and develop long-lasting diabetic symptoms and some complications from about 40 weeks of age without any treatment. A single intravenous dose of alloxan, a non-genotoxic diabetogenic chemical, frequently induced proliferative lesions of squamous epithelium in tongue, esophagus and forestomach of male and female WBN/Kob rats, and hastened the onset and acceleration of diabetic conditions. Histopathologically, proliferative changes of squamous cell of forestomach varied with the severity of hyperplasia in alloxan-treated rats (100% of 31 males and 94.1% of 17 females) and progressed to SCC in approximately 20% of all rats. Metastasis to regional lymph nodes was also observed in two cases. Proliferative changes were most severe in the forestomach and were constantly accompanied with chronic suppurative inflammation of the mucosal epithelium with infection of filamentous fungi and/or bacterial colonies. In contrast, forestomach of the spontaneously diabetic male rats showed only slight hyperplasia of the mucosal epithelium confined to the limiting ridge in approximately 30% of the cases. All non-diabetic female rats showed neither proliferative changes nor the inflammatory process in the mucosa. Immunohistochemically, COX-2 and iNOS were positive in these chronic suppurative inflammatory lesions accompanied by proliferative squamous epithelium. From these results, it is suggested that chronic inflammatory processes play an important role in the pathogenesis of alloxan-induced SCC. An experimental system of alloxan-induced SCC might serve as a suitable model for the study of the inflammation-related promotion of carcinogenesis.

Protein kinase Cepsilon and development of squamous cell carcinoma, the nonmelanoma human skin cancer.

Protein kinase C (PKC) represents a large family of phosphatidylserine (PS)-dependent serine/threonine protein kinases. At least five PKC isoforms (alpha, delta, epsilon, eta, and zeta) are expressed in epidermal keratinocytes. PKC isoforms are differentially expressed in proliferative (basal layer) and nonproliferative compartments (spinous, granular, cornified layers), which exhibit divergence in their roles in the regulation of epidermal cell proliferation, differentiation, and apoptosis. Immunocytochemical localization of PKC isoforms indicate that PKCalpha is found in the membranes of suprabasal cells in the spinous and granular layers. PKCepsilon is mostly localized in the proliferative basal layers. PKCeta is localized exclusively in the granular layer. PKCdelta is detected throughout the epidermis. PKC isozymes exhibit specificities in their signals to the development of skin cancer. PKCepsilon, a calcium-insensitive PKC isoform mediates the induction of squamous cell carcinoma (SCC) elicited either by the DMBA-TPA protocol or by repeated exposures to ultraviolet radiation (UVR). PKCepsilon overexpression, which sensitizes skin to UVR-induced carcinogenesis, suppresses UVR-induced sunburn (apoptotic) cell formation, and enhances both UVR-induced levels of TNFalpha and hyperplasia. UVR-induced sunburn cell formation is mediated by Fas/Fas-L and TNFalpha NFR1 extrinsic apoptotic pathways. The death adaptor protein termed Fas-associated death domain (FADD) is a common adaptor protein for both of these apoptotic pathways. PKCepsilon inhibits UVR-induced expression of FADD leading to the inhibition of both apoptotic pathways. It appears that PKCepsilon sensitizes skin to the development of SCC by UVR by transducting signals, which inhibit apoptosis on one hand, and enhances proliferation of preneoplastic cells on the other hand.

Protein kinase C delta overexpressing transgenic mice are resistant to chemically but not to UV radiation-induced development of squamous cell carcinomas: a possible link to specific cytokines and cyclooxygenase-2.

Protein kinase C delta (PKCdelta), a Ca(2+)-independent, phospholipid-dependent serine/threonine kinase, is among the novel PKCs (delta, epsilon, and eta) expressed in mouse epidermis. We reported that FVB/N transgenic mice that overexpress ( approximately 8-fold) PKCdelta protein in basal epidermal cells and cells of the hair follicle are resistant to the development of both skin papillomas and squamous cell carcinoma (SCC) elicited by 7,12-dimethylbenz(a)anthracene initiation and 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion protocol. We now present that PKCdelta overexpression in transgenic mice failed to suppress the induction of SCC developed by repeated exposures to UV radiation (UVR), the environmental carcinogen linked to the development of human SCC. Both TPA and UVR treatment of wild-type mice (a) increased the expression of proliferating cell nuclear antigen (PCNA) and apoptosis; (b) stimulated the expression of cytokines tumor necrosis factor-alpha (TNF-alpha), granulocyte macrophage colony-stimulating factor (GM-CSF), and granulocyte CSF (G-CSF); and (c) increased cyclooxygenase-2 (COX-2) expression and expression of phosphorylated Akt (p-Akt), p38, extracellular signal-regulated kinase-1 (ERK1), and ERK2. PKCdelta overexpression in transgenic mice enhanced TPA-induced but not UVR-induced apoptosis and suppressed TPA-stimulated but not UVR-stimulated levels of cell PCNA, cytokines (TNF-alpha, G-CSF, and GM-CSF), and the expression of COX-2, p-Akt, and p38. The results indicate that UVR-mediated signal transduction pathway to the induction of SCC does not seem to be sensitive to PKCdelta overexpression. The proapoptotic activity of PKCdelta coupled with its ability to suppress TPA-induced expression of proinflammatory cytokines, COX-2 expression, and the phosphorylation of Akt and p38 may play roles in the suppression of TPA-promoted development of SCC.