Small-molecule inhibitors of Ataxia Telangiectasia and Rad3 related kinase (ATR) sensitize lymphoma cells to UVA radiation. Issue 3 (December 2016)

• Record Type: Journal Article
• Authors: Biskup, Edyta; Naym, David Gram; Gniadecki, Robert
• Is Part Of: Journal of dermatological science. Volume 84:Issue 3(2016:Dec.)
• Page Start: 239
• Page End: 247
• Publication Date: 2016-12
• Subjects: ATR inhibitors -- VE-821 -- VE-822 -- Cutaneous T-cell lymphoma -- DNA damage; Dermatology -- Periodicals; Skin Diseases -- Periodicals; Dermatologie -- Périodiques; 616.5005
• DOI: 10.1016/j.jdermsci.2016.09.010
• Languages: English
• ISSNs: 0923-1811

Abstract

Highlights: Chemical inhibitors of Ataxia Telangiectasia and Rad 3 kinase (ATR), VE-821 and VE-822, potently sensitize cutaneous T-cell lymphoma cells to UVA radiation. The synergism between VE-821/2 and UVA is not solely caused by specific blocking of ATR kinase, but also due to ATR-independent photosensitization. ATR inhibitors have potential to be used as photosensitizers in photochemotherapeutic regimes for cutaneous lymphomas. Abstract: Background: Psoralen plus ultraviolet A (PUVA) photochemotherapy is a combination treatment used for inflammatory and neoplastic skin diseases such as mycosis fungoides (MF), the most common type of cutaneous T-cell lymphoma (CTCL). However, 30% of MF patients do not respond sufficiently to PUVA and require more aggressive therapies. Objective: The aim of this project was to investigate whether inhibition of Ataxia Telangiectasia and Rad3 related kinase (ATR) may enhance efficacy of phototherapy. Methods: CTCL cell lines (MyLa2000, SeAx and Mac2a) served as in vitro cell models. ATR and Chk1 were inhibited by small molecule antagonists VE-821, VE-822 or Chir-124, or by small interfering RNAs (siRNAs). Cell cycle and viability were assessed by flow cytometry. Results: Small molecule inhibitors of ATR and Chk1 potently sensitized all cell lines to PUVA and, importantly, also to UVA, which by itself did not cause apoptotic response. VE-821/2 blocked ATR pathway activation and released the cells from the G2/M block caused by UVA and PUVA, but did not affect apoptosis caused by other chemotherapeutics (etoposide, gemcitabine, doxorubicine) or by hydrogen peroxide. Knockdown of ATR and Chk1 with siRNA also blocked the ATR pathway and released the cells from G2/M block but did not sensitize the cells to UVA as observed with the small molecule inhibitors. The latter suggested that the synergism between VE-821/2 or Chir-124 and UVA was not solely caused by specific blocking of ATR kinase but also ATR-independent photosensitization. This hypothesis was further verified by administrating VE-821/2 or Chir-124 before and after UVA irradiation, as well as comparing their activity with other ATR and Chk1 inhibitors (AZD6738 and MK8776). We found that only VE-821/2 and Chir-124 kinase inhibitors had synergistic effect with UVA, and only if applied before treatment with UVA. Conclusion: Small molecule ATR and Chk1 inhibitors potently sensitize lymphoma cells to UVA radiation and induce a prominent apoptotic response. Interestingly, this effect is due to the dual (kinase inhibiting and photosensitizing) mode of action of these compounds.