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Biomedical Science
Abstract
Background: Maintaining a balance between keratinocyte proliferation and differentiation is essential for epidermal homeostasis. Disruption of this balance can lead to hyperplasia and cancer. Epidermal homeostasis is regulated by various signaling pathways, including those mediated by reciprocal regulation between protein tyrosine kinases and protein tyrosine phosphatases. T-cell protein tyrosine phosphatase (TC-PTP), encoded by the PTPN2 gene, is one such phosphatase known to inhibit epidermal cell proliferation through the direct dephosphorylation of STAT3, a key transcription factor involved in cell survival and proliferation following exposure to chemical toxicants. Our previous studies have demonstrated the crucial role of TC-PTP in the prevention of skin cancer formation induced by chemical carcinogenesis by regulating apoptosis and cell proliferation. This study aims to determine whether TC-PTP plays a role in tumor promoter TPA (12-O-tetradecanoylphorbol-13-acetate) induced epidermal differentiation.
Methods: Immortalized primary keratinocytes (IPKs) derived from either wild-type FVB mice (TC-PTP/WT) or transgenic mice overexpressing TC-PTP (TG4-1) were cultured under standard conditions. Both cell types were exposed to TPA for 12, 24, 48, and 72 hours. Following TPA treatment, cells were collected at each time point for protein extraction and quantification. Western blot analysis was performed to measure the expression levels of differentiation markers, including cytokeratin 1 (CK1), transglutaminase 1 (TG1), and involucrin, as well as proliferation markers such as proliferating cell nuclear antigen (PCNA) and Ki67. For in vivo analysis, groups of wild-type and TC-PTP overexpressing mice were treated with TPA, and dorsal skin samples were collected at 24-, 48-, and 72-hours post-treatment. The skin samples were fixed in 10% neutral-buffered formalin, embedded in paraffin, and sectioned for immunofluorescent analysis to examine the expression of differentiation markers (involucrin, loricrin, and CK10).
Results: TC-PTP overexpressing cells exhibited significantly higher expression levels of differentiation markers (CK1, TG1, and involucrin) at all examined time points compared to wild-type cells. Conversely, proliferation markers (PCNA and Ki67) were more prominently expressed in wild-type cells. In the in vivo analysis, the epidermis of TC-PTP overexpressing mice showed increased expression of differentiation markers and decreased expression of the proliferation marker PCNA compared to wild-type mice. These results suggest that TC-PTP overexpression enhances the differentiation response of keratinocytes to TPA exposure, indicating its potential protective function against skin tumor promotion.
Conclusion: Our findings provide new insights into the molecular mechanisms by which TC-PTP regulates epidermal differentiation in response to TPA treatment. Understanding these mechanisms could inform the development of novel therapeutic strategies for skin disorders and cancer prevention.
Presentation Type
Poster
Recommended Citation
Hensley, Jared; Marupudi, Smaran; Shim, Lindsey; Hafeez, Bilal; and Joon Kim, Dae, "TC-PTP Overexpression in Mouse Skin is Linked to Enhanced Epidermal Differentiation in Response to Tumor Promoter TPA Exposure" (2024). Research Colloquium. 56.
https://scholarworks.utrgv.edu/colloquium/2024/posters/56
Included in
TC-PTP Overexpression in Mouse Skin is Linked to Enhanced Epidermal Differentiation in Response to Tumor Promoter TPA Exposure
Background: Maintaining a balance between keratinocyte proliferation and differentiation is essential for epidermal homeostasis. Disruption of this balance can lead to hyperplasia and cancer. Epidermal homeostasis is regulated by various signaling pathways, including those mediated by reciprocal regulation between protein tyrosine kinases and protein tyrosine phosphatases. T-cell protein tyrosine phosphatase (TC-PTP), encoded by the PTPN2 gene, is one such phosphatase known to inhibit epidermal cell proliferation through the direct dephosphorylation of STAT3, a key transcription factor involved in cell survival and proliferation following exposure to chemical toxicants. Our previous studies have demonstrated the crucial role of TC-PTP in the prevention of skin cancer formation induced by chemical carcinogenesis by regulating apoptosis and cell proliferation. This study aims to determine whether TC-PTP plays a role in tumor promoter TPA (12-O-tetradecanoylphorbol-13-acetate) induced epidermal differentiation.
Methods: Immortalized primary keratinocytes (IPKs) derived from either wild-type FVB mice (TC-PTP/WT) or transgenic mice overexpressing TC-PTP (TG4-1) were cultured under standard conditions. Both cell types were exposed to TPA for 12, 24, 48, and 72 hours. Following TPA treatment, cells were collected at each time point for protein extraction and quantification. Western blot analysis was performed to measure the expression levels of differentiation markers, including cytokeratin 1 (CK1), transglutaminase 1 (TG1), and involucrin, as well as proliferation markers such as proliferating cell nuclear antigen (PCNA) and Ki67. For in vivo analysis, groups of wild-type and TC-PTP overexpressing mice were treated with TPA, and dorsal skin samples were collected at 24-, 48-, and 72-hours post-treatment. The skin samples were fixed in 10% neutral-buffered formalin, embedded in paraffin, and sectioned for immunofluorescent analysis to examine the expression of differentiation markers (involucrin, loricrin, and CK10).
Results: TC-PTP overexpressing cells exhibited significantly higher expression levels of differentiation markers (CK1, TG1, and involucrin) at all examined time points compared to wild-type cells. Conversely, proliferation markers (PCNA and Ki67) were more prominently expressed in wild-type cells. In the in vivo analysis, the epidermis of TC-PTP overexpressing mice showed increased expression of differentiation markers and decreased expression of the proliferation marker PCNA compared to wild-type mice. These results suggest that TC-PTP overexpression enhances the differentiation response of keratinocytes to TPA exposure, indicating its potential protective function against skin tumor promotion.
Conclusion: Our findings provide new insights into the molecular mechanisms by which TC-PTP regulates epidermal differentiation in response to TPA treatment. Understanding these mechanisms could inform the development of novel therapeutic strategies for skin disorders and cancer prevention.