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Drug resistance is a major problem in treatment with nelarabine, and its resolution requires elucidation of the underlying mechanisms. We established two nelarabine-resistant subclones of the human T-cell lymphoblastic leukemia cell line CCRF-CEM. The resistant subclones showed changes in the expression of several genes related to nelarabine intracellular activation and inhibition of apoptosis. Activation of the Akt protein upon nelarabine treatment was observed in both subclones. The combination treatment with nelarabine and PI3K/Akt inhibitors was shown to inhibit cell growth. Cross-resistance was observed with ara-C and not with vincristine, daunorubicin, or etoposide treatment. Thus, changes in the expression of cellular activation-related genes, inhibition of apoptosis, and induction of Akt may be involved in the development of nelarabine resistance in the CCRF-CEM cell model. The use of different classes of chemotherapeutic agents and combination therapy with PI3K/Akt pathway inhibitors may be used to overcome resistance to nelarabine.

Approximately 20% of pediatric patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) relapse or are refractory to chemotherapy despite the low frequency of TP53 mutations. The nucleolar stress response is a P53-activating mechanism via MDM2 inhibition by ribosomal protein L11 (RPL11). We analyzed the role of the nucleolar stress response using BCP-ALL cell lines and patient samples by drug sensitivity tests, Western blotting, and reverse transcription polymerase chain reaction. We revealed that the nucleolar stress response works properly in TP53 wild-type human BCP-ALL cell lines. Next, we found that 6-mercaptopurine, methotrexate, daunorubicin, and cytarabine had anti-leukemic effects via the nucleolar stress response within BCP-ALL treatment. Comparing the samples at onset and relapse in children with BCP-ALL, RPL11 mRNA expression decreased at relapse in seven of nine cases. Furthermore, leukemia cells with relapse acquired resistance to these four drugs and suppressed P53 and RPL11 expression. Our findings suggest that the nucleolar stress response is a novel anti-leukemia mechanism in BCP-ALL. As these four drugs are key therapeutics for BCP-ALL treatment, dysfunction of the nucleolar stress response may be related to clinical relapse or refractoriness. Nucleolar stress response may be a target to predict and improve the chemotherapy effect for pediatric BCP-ALL.

The pathogenesis of cyclophosphamide (CY)-induced cardiotoxicity remains unknown, and methods for its prevention have not been established. To elucidate acute structural changes in myocardial cells and pathways leading to myocardial damage in mice treated with high-dose CY, we performed detailed pathological analyses of myocardial tissue obtained from C57BL/6J mice that received high-dose CY. In addition, we analyzed the genome-wide cardiomyocyte expression profile of mice that received high-dose CY. Treatment with CY caused marked ultrastructural aberrations with electron microscopy, although these could not be observed with optical microscopy. Expansion of the transverse tubule and sarcoplasmic reticulum, turbulence of myocardial fiber travel, and low contractile protein density in cardiomyocytes were observed. High-dose CY treatment changed cardiomyocyte expression of 1,210 genes associated with cell-cell junctions, inflammatory responses, cardiomyopathy, and cardiac muscle function, as detected by microarray analysis (│Z-score│ > 2.0). The expression of functionally important genes related to myocardial contraction and the regulation of calcium ions was validated using real-time polymerase chain reaction analysis. Our results of gene expression profiles, functional annotation clustering, and the Kyoto Encyclopedia of Genes and Genomes pathway functional classification analysis suggest that cardiotoxicity induced by CY is associated with a disruption of the Ca2+ signaling pathway.

Persistent cloaca involves fusion of the bladder, vagina, and rectum into a single duct called the common duct. Although its pathogenesis remains unclear, it has been associated with hyperchloremic metabolic acidosis. Herein, we present the case of a neonatal girl with high-confluence type variant of persistent cloaca treated with vesicostomy (Blocksom) for refractory metabolic acidosis. She was diagnosed with persistent cloaca before birth; colostomy was performed and a urinary catheter was placed in the bladder. Voiding cystourethrography on day 19 after birth showed that most of the contrast material leaked into the rectum; hence, the urinary catheter was removed. On day 27, hyperchloremic metabolic acidosis was detected and treatment with oral sodium bicarbonate was initiated; however, the infant showed no response. Because hyperchloremia occurred after removal of the urinary catheter, continuous urine retention in the colon through the common duct was believed to have caused the progression of hyperchloremic metabolic acidosis through transporters in the intestinal mucosa. As reinstallation of a urinary catheter was technically difficult, vesicostomy was performed on day 29, after which the metabolic acidosis improved. This report suggests vesicostomy as an effective treatment for refractory hyperchloremic metabolic acidosis associated with high-confluence type persistent cloaca.