Abstract 2558: Loss of TC-PTP in keratinocytes leads to increased UVB-induced autophagy

Abstract

Abstract Amongst the deteriorating effects of the sun’s ultraviolet B (UVB) radiation on cellular homeostasis is the formation of photoproducts in the DNA, such as cyclobutene pyrimidine dimers. Photoproducts cause conformational alterations in the DNA structure which may evade cellular repair machinery and persist through DNA replication processes, leading to potential gene mutations and ultimately leading to skin cancer. Photoproducts are typically repaired by nucleotide excision repair. Notwithstanding, when the repair mechanism fails, apoptosis ensues to prevent the accumulation of mutations and to restore cellular homeostasis. T-cell protein tyrosine phosphatase (TC-PTP) is one of the members of PTP family that has been shown to increase UVB-induced apoptosis in keratinocytes via the downregulation of Flk-1/JNK signaling. This implies that loss of TC-PTP causes resistance to apoptosis in UVB-damaged keratinocytes. In the present work, we report that this resistance is accompanied by an increase in UVB-induced autophagy in the absence of TC-PTP. We generated human TC-PTP-deficient (TC-PTP/KO) HaCaT keratinocytes using CRISPR/Cas9 system. The expression of microtubule-associated protein light chain 3 (LC3) was significantly increased in TC-PTP/KO HaCaT keratinocytes compared to engineered controls (TC-PTP/Mock) following treatment with UVB irradiation. Increased expression of LC3 in TC-PTP/KO keratinocytes was accompanied by a significant decrease in the expression of the p62. We also observed that treatment of TC-PTP KO keratinocytes with chloroquine (CQ), a late-phase autophagy inhibitor, caused a remarkable increase in LC3 expression following UVB exposure in comparison with untreated TC-PTP/KO keratinocytes, implying that loss of TC-PTP increases autophagy in response to UVB. With this regard, TC-PTP deficiency in human keratinocytes significantly increased cell proliferation following UVB exposure compared to similarly treated control keratinocytes. Pretreatment of CQ before UVB irradiation in TC-PTP KO keratinocytes significantly reduced cell viability compared to untreated TC-PTP KO keratinocytes. These results suggest that TC-PTP protects keratinocytes from UVB-induced damage by negatively regulating autophagy signaling. Citation Format: Obed Asare, Klarissa Zavala, Lindsey Shim, Bilal Hafeez, Dae Kim. Loss of TC-PTP in keratinocytes leads to increased UVB-induced autophagy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2558.