Despite clinical recovery of patients from an episode of acute kidney injury (AKI), progression to chronic kidney disease (CKD) is possible on long-term follow-up. However, mechanisms of this are poorly understood. Here, we determine whether activation of angiotensin-II type 1 receptors during AKI triggers maladaptive mechanisms that lead to CKD. Nine months after AKI, male Wistar rats develop CKD characterized by renal dysfunction, proteinuria, renal hypertrophy, glomerulosclerosis, tubular atrophy, and tubulointerstitial fibrosis. Renal injury was associated with increased oxidative stress, inflammation, α-smooth muscle actin expression, and activation of transforming growth factor β; the latter mainly found in epithelial cells. Although administration of losartan prior to the initial ischemic insult did not prevent or reduce AKI severity, it effectively prevented eventual CKD. Three days after AKI, renal dysfunction, tubular structural injury, and elevation of urinary biomarkers were present. While the losartan group had similar early renal injury, renal perfusion was completely restored as early as day 3 postischemia. Further, there was increased vascular endothelial growth factor expression and an early activation of hypoxia-inducible factor 1 α, a transcription factor that regulates expression of many genes that help reduce renal injury. Thus, AT1 receptor antagonism prior to ischemia prevented AKI to CKD transition by improving early renal blood flow recovery, lesser inflammation, and increased hypoxia-inducible factor 1 α activity.

HIF-1α has a dual role in experimental TB. This finding could have therapeutic implications because combined treatment with 2-methoxyestradiol and antibiotics appeared to eliminate mycobacteria more efficiently than conventional chemotherapy during advanced disease.

Resistance to chemotherapy hinders the successful treatment of acute lymphoblastic leukemia (ALL). The multi-drug resistance-1 (MDR1/ABCB1) gene encodes P-glycoprotein (P-gp), which plays an important role in chemoresistance; however, its transcriptional regulation remains unclear. We investigated the role of YY1 in the regulation of MDR1 and its relation to ALL outcomes. Analysis of the MDR1 promoter revealed four putative YY1-binding sites, which we analyzed using a reporter system and ChIP analysis. YY1 silencing resulted in the inhibition of MDR1 expression and function. The clinical roles of YY1 and MDR1 expression were evaluated in children with ALL. Expression of both proteins was increased in ALL patients compared to controls. We identified a positive correlation between YY1 and MDR1 expression. High levels of YY1 were associated with decreased overall survival. Our results demonstrated that YY1 regulates the transcription of MDR1. Therefore, YY1 may serve as a useful prognostic and/or therapeutic target.

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Leukemia is the most common cancer among children under the age of 15 years in the United States and many developed countries. In recent years, there has been the emergence of novel therapeutic drugs for this disease. However, the development of drug resistance by the tumor cells remains the most important obstacle in the treatment of leukemia. A widely studied mechanism of tumor resistance to chemotherapeutic drugs is through the expression of the multi-drug resistance (MDR) genes. P-glycoprotein 170 (gp170) is an MDR1 gene product which serves as an ATP-dependent cell membrane transporter; it facilitates the efflux of xenobiotics from the cells to prevent damage for prolonged drug activity, including chemotherapeutics agents. In addition to MDR1, several reports in different cancers have indicated that the transcription factor Yin Yang 1 (YY1) is over-expressed and regulates tumor cell response to chemotherapeutic drugs. TESS analysis demonstrated that the gp170 proximal promoter contains four putative binding sites for the YY-1 protein. We also hypothesized that the YY1 may too be over-expressed in ALL and that its expression may be correlated with the expression of gp170. These hypotheses were examined first by reporter systems analyze, the gp170 protein was cloned and we developed a luciferase reporter assay. Examination of the putative YY1 binding sites that were individually mutated (deleted), showed revealed that mutation at the site –1860 abolished the activity. Mutation at the site –1920 abolished approximately 50% and mutation at –1230 site abolished approximately 25%. Further, CHIP analysis demonstrated that YY1 transcription factor binds directly to the gp170 gene MDR1 promoter. In addition, we examined the expression of YY1 and gp170 in childhood ALL (n= 84). The expression of YY1 and gp170 was determined evaluated by IHC in tumor tissues and the frequency of positive cells was determined. For comparison, normal controls were also analyzed (n=53). The findings demonstrate that were a significant increase in the frequency of positive cells in ALL compared to controls for both YY1 (38% vs. 8%, p=0.001) and for gp170 (42% vs. 12%, p=0.001). There was a good correlation between the expression of YY1 and gp170 (Pearson's test, r=0.4, p=0.001). The findings suggest that YY1 transcriptionally regulates the mdr1 and may be a therapeutic target in MDR positive ALL and its inhibition may reverse resistance to chemotherapeutic drugs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4330. doi:1538-7445.AM2012-4330

3567 Leukemia is the most common cancer among children under the age of 15 years in the United States and many developed countries. In recent years, there has been the emergence of novel therapeutic drugs for this disease. However, the development of drug resistance by the tumor cells remains the most important obstacle in the treatment of leukemia. A widely studied mechanism of tumor resistance to chemotherapeutic drugs is through the expression of the multi-drug resistance (MDR) genes. P-glycoprotein 170 (gp-170) is an MDR1 gene product which serves as an ATP-dependent cell membrane transporter; it facilitates the efflux of xenobiotics (including chemotherapeutic drugs) from the cells to prevent damage for prolonged drug activity, including chemotherapeutics agents. In addition to MDR1, several reports in different cancers have indicated that the transcription factor Yin Yang 1 (YY1) is over-expressed and regulates tumor cell response to chemotherapeutic drugs. Thus, we hypothesized that YY1 may also be over-expressed in ALL and that its expression may be correlated with the expression of gp-170. We also hypothesized that the co-expression of YY1 and gp-170 may be of prognostic significance in high risk ALL patients. These hypotheses were examined with childhood ALL (n= 88) (of median age 8.2 years, range 0.21–16). The expression of YY1 and gp-170 was determined by IHC in tumor tissues and the frequency of YY1 positive cells was determined. For comparison, normal controls were also analyzed (n= 53). The findings demonstrate that were a significant increase in the frequency of positive cells in ALL compared to controls for both YY1 (38% vs. 8%, p= 0.0001) and for gp-170 (42% vs. 12%, p= 0.001). There was a good correlation between the expression of YY1 and gp-170 using Pearson's test, r=0.4, p=0.0001. We then examined if the co-expression of YY1 and gp-170 is also associated with decreased risk. Indeed, patients with low risk (L1) had significantly less frequency of positive cells compared to patients with high risk for both YY1 (40% vs. 30%, p=0.045) and for gp-170 (48% vs. 35%, p=0.0003). The strong correlation betweenYY1 and gp-170 expression suggested that there may be a cross-talk. TESS analysis demonstrated that the gp-170 proximal promoter contains four putative binding sites for the YY-1 protein. The gp-170 protein was cloned and we developed a luciferase reporter assay. Examination of the putative YY1 binding sites that were individually mutated revealed that mutation at the sites -1860 and -270 abolished activity. Mutation at the site -1420 abolished approximately 50% and mutation at -1230 abolished approximately 75%. Further, CHIP analysis demonstrated that YY1 binds directly to the gp-170 gene. Transfection of cells with YY1 siRNA inhibited the efflux of adriamycin from the cells confirming the regulation of gp-170 expression by YY1. Overall, the findings above demonstrate that both gp-170 and YY1 are over-expressed in childhood ALL and further over-expressed in patients with high risk. The findings suggest that YY1 may be a therapeutic target in MDR positive ALL and its inhibition may reverse resistance to chemotherapeutic drugs. Disclosures: No relevant conflicts of interest to declare.