Timing of cisplatin administration for chemoradiotherapy in transgenic mice bearing lens tumors

p53 as a unique target of action of cisplatin in acute leukaemia cells

Acute promyelocytic leukaemia (APL) occurs in approximately 10% of acute myeloid leukaemia patients. Arsenic trioxide (ATO) has been for APL chemotherapy, but recently several ATO-resistant cases have been reported worldwide. Cisplatin (CDDP) enhances the toxicity of ATO in ovarian, lung cancer, chronic myelogenous leukaemia, and HL-60 cells. Hence, the goal of this study was to investigate a novel target of CDDP action in APL cells, as an alternate option for the treatment of ATO-resistant APL patients. We applied biochemical, molecular, confocal microscopy and advanced gene editing (CRISPR-Cas9) techniques to elucidate the novel target of CDDP action and its functional mechanism in APL cells. Our main findings revealed that CDDP activated p53 in APL cells through stress signals catalysed by ATM and ATR protein kinases, CHK1 and CHK2 phosphorylation at Ser 345 and Thr68 residues, and downregulation and dissociation of MDM2-DAXX-HAUSP complex. Our functional studies confirmed that CDDP-induced repression of MDM2-DAXX-HAUSP complex was significantly reversed in both nutilin-3-treated KG1a and p53-knockdown NB4 cells. Our findings also showed that CDDP stimulated an increased number of promyelocytes with dense granules, activated p53 expression, and downregulated MDM2 in liver and bone marrow of APL mice. Principal conclusion of our study highlights a novel mode of action of CDDP targeting p53 expression which may provide a basis for designing new anti-leukaemic compounds for treatment of APL patients.

Divergent effects of AKI to CKD models on inflammation and fibrosis

Chronic kidney disease (CKD) is a condition with significant morbidity and mortality that affects 15% of adults in the United States. One cause of CKD is acute kidney injury (AKI), which commonly occurs secondary to sepsis, ischemic events, and drug-induced nephrotoxicity. Unilateral ischemia-reperfusion injury (UIRI) without contralateral nephrectomy (CLN) and repeated low-dose cisplatin (RLDC) models of AKI to CKD demonstrate responses characteristic of the transition; however, previous studies have not effectively compared the pathogenesis. We demonstrate both models instigate renal dysfunction, inflammatory cytokine responses, and fibrosis. However, the models exhibit differences in urinary excretory function, inflammatory cell infiltration, and degree of fibrotic response. UIRI without CLN demonstrated worsening perfusion and function, measured with ^99mTc-mercaptoacetyltriglycine-3 imaging, and physiologic compensation in the contralateral kidney. Furthermore, UIRI without CLN elicited a robust inflammatory response that was characterized by a prolonged polymorphonuclear cell and natural killer cell infiltrate and an early expansion of kidney resident macrophages, followed by T-cell infiltration. Symmetrical diminished function occurred in RLDC kidneys and progressively worsened until day 17 of the study. Surprisingly, RLDC mice demonstrated a decrease in inflammatory cell numbers relative to controls. However, RLDC kidneys expressed increased levels of kidney injury molecule-1 (KIM-1), high mobility group box-1 ( HMGB1), and colony stimulating factor-1 ( CSF-1), which likely recruits inflammatory cells in response to injury. These data emphasize how the divergent etiologies of AKI to CKD models affect the kidney microenvironment and outcomes. This study provides support for subtyping AKI by etiology in human studies, aiding in the elucidation of injury-specific pathophysiologic mechanisms of the AKI to CKD transition.