In-vivo evaluation of human recombinant Co-arginase against A375 melanoma xenografts.

Metastatic melanoma is a deadly form of cancer with few therapeutic options and the cause of more than 9480 deaths annually in the USA alone. Novel treatment options for this disease are urgently needed. Here we test the efficacy of a novel melanoma drug, the human recombinant Co-arginase (CoArgIPEG), against an aggressive A375 melanoma mouse model. CoArgIPEG is a modification of the naturally occurring human enzyme with improved stability, catalytic activity, and potentially lower immunogenicity compared with current amino acid-depleting drugs. Marked tumor growth reductions (mean P=0.0057) with apoptosis induction and proliferation inhibition are noted with CoArgIPEG treatment, both in the presence and in the absence of supplemental citrulline. Further, improved therapeutic efficacy has been noted against A375 xenografts relative to the naturally occurring human recombinant arginase enzyme at lower doses of CoArgIPEG. Unfortunately, after 1 month, half of the relapsing tumors showed argininosuccinate synthase induction, which correlated with Ser62-phosphorylated cMyc. Although argininosuccinate synthase induction could not be induced in vitro, a drug targeting pathway previously demonstrated to be associated with Ser62 cMyc phosphorylation - U0126 - in combination with CoArgIPEG demonstrated an in-vitro synergistic response (combination indices 0.13±0.10 and 0.14±0.10 with or without citrulline, respectively). Overall, favorable efficacy and potential synergy with other antimelanoma drugs support CoArgIPEG as a potent, novel cancer therapeutic.

Treatment of metabolic acidosis in patients with stage 3 chronic kidney disease with fruits and vegetables or oral bicarbonate reduces urine angiotensinogen and preserves glomerular filtration rate.

Alkali therapy of metabolic acidosis in patients with chronic kidney disease (CKD) with plasma total CO2 (TCO2) below 22 mmol/l per KDOQI guidelines appears to preserve estimated glomerular filtration rate (eGFR). Since angiotensin II mediates GFR decline in partial nephrectomy models of CKD and even mild metabolic acidosis increases kidney angiotensin II in animals, alkali treatment of CKD-related metabolic acidosis in patients with plasma TCO2 over 22 mmol/l might preserve GFR through reduced kidney angiotensin II. To test this, we randomized 108 patients with stage 3 CKD and plasma TCO2 22-24 mmol/l to Usual Care or interventions designed to reduce dietary acid by 50% using sodium bicarbonate or base-producing fruits and vegetables. All were treated to achieve a systolic blood pressure below 130 mm Hg with regimens including angiotensin converting enzyme inhibition and followed for 3 years. Plasma TCO2 decreased in Usual Care but increased with bicarbonate or fruits and vegetables. By contrast, urine excretion of angiotensinogen, an index of kidney angiotensin II, increased in Usual Care but decreased with bicarbonate or fruits and vegetables. Creatinine-calculated and cystatin C-calculated eGFR decreased in all groups, but loss was less at 3 years with bicarbonate or fruits and vegetables than Usual Care. Thus, dietary alkali treatment of metabolic acidosis in CKD that is less severe than that for which KDOQI recommends therapy reduces kidney angiotensin II activity and preserves eGFR.

A comparison of treating metabolic acidosis in CKD stage 4 hypertensive kidney disease with fruits and vegetables or sodium bicarbonate.

BACKGROUND AND OBJECTIVES: Current guidelines recommend Na(+)-based alkali for CKD with metabolic acidosis and plasma total CO2 (PTCO2) < 22 mM. Because diets in industrialized societies are typically acid-producing, we compared base-producing fruits and vegetables with oral NaHCO3 (HCO3) regarding the primary outcome of follow-up estimated GFR (eGFR) and secondary outcomes of improved metabolic acidosis and reduced urine indices of kidney injury. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Individuals with stage 4 (eGFR, 15-29 ml/min per 1.73 m(2)) CKD due to hypertensive nephropathy, had a PTCO2 level < 22 mM, and were receiving angiotensin-converting enzyme inhibition were randomly assigned to 1 year of daily oral NaHCO3 at 1.0 mEq/kg per day (n=35) or fruits and vegetables dosed to reduce dietary acid by half (n=36). RESULTS: Plasma cystatin C-calculated eGFR did not differ at baseline and 1 year between groups. One-year PTCO2 was higher than baseline in the HCO3 group (21.2±1.3 versus 19.5±1.5 mM; P<0.01) and the fruits and vegetables group (19.9±1.7 versus 19.3±1.9 mM; P<0.01), consistent with improved metabolic acidosis, and was higher in the HCO3 than the fruits and vegetable group (P<0.001). One-year urine indices of kidney injury were lower than baseline in both groups. Plasma [K(+)] did not increase in either group. CONCLUSIONS: One year of fruits and vegetables or NaHCO3 in individuals with stage 4 CKD yielded eGFR that was not different, was associated with higher-than-baseline PTCO2, and was associated with lower-than-baseline urine indices of kidney injury. The data indicate that fruits and vegetables improve metabolic acidosis and reduce kidney injury in stage 4 CKD without producing hyperkalemia.

Cytotoxicity of human recombinant arginase I (Co)-PEG5000 in the presence of supplemental L-citrulline is dependent on decreased argininosuccinate synthetase expression in human cells.

Human recombinant arginase I cobalt [HuArgI (Co)] coupled with polyethylene glycol 5000 [HuArgI (Co)-PEG5000] has shown potent in-vitro depletion of arginine from tissue culture medium. We now show that HuArgI (Co)-PEG5000 is toxic to almost all cancer cell lines and to some normal primary cells examined. In contrast, HuArgI (Co)-PEG5000 in combination with supplemental L-citrulline is selectively cytotoxic to a fraction of human cancer cell lines in tissue culture, including some melanomas, mesotheliomas, acute myeloid leukemias, hepatocellular carcinomas, pancreas adenocarcinomas, prostate adenocarcinomas, lung adenocarcinomas, osteosarcomas, and small cell lung carcinomas. Unfortunately, a subset of normal human tissues is also sensitive to HuArgI (Co)-PEG5000 with L-citrulline supplementation, including umbilical endothelial cells, bronchial epithelium, neurons, and renal epithelial cells. We further show that cell sensitivity is predicted by the level of cellular argininosuccinate synthetase protein expression measured by immunoblots. By comparing a 3-day and 7-day exposure to HuArgI (Co)-PEG5000 with supplemental L-citrulline, some tumor cells sensitive on short-term assay are resistant in the 7-day assay consistent with the induction of argininosuccinate synthetase expression. On the basis of these results, we hypothesize that HuArgI (Co)-PEG5000 in combination with L-citrulline supplementation may be an attractive therapeutic agent for some argininosuccinate synthetase-deficient tumors. These in-vitro findings stimulate further development of this molecule and may aid in the identification of tissue toxicities and better selection of patients who will potentially respond to this combination therapy.

Dehydroepiandrosterone intake protects against 7,12-dimethylbenz(a)anthracene-induced mammary tumor development in the obese Zucker rat model.

Obesity has been epidemic in the US for over two decades; almost 65% of adults in the US are overweight. Obesity has been linked with the risk of development of various cancers, including breast cancer. Dehydroepiandrosterone (DHEA) is an over-the-counter dietary supplement used as an immunomodulating, anti-depressant, anti-aging, anti-cardiovascular disease, and anti-cancer agent and anti-obesity supplement. The objectives of this study were to investigate the long-term effects of obesity and DHEA treatment on body weight gain and on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumor development. Forty-three six-week-old obese female Zucker rats were used. Rats were randomly assigned and had ad libitum access to water and a diet of either chow (2016) as a control diet or chow with the addition of DHEA at a concentration of 6 g/kg of chow as a DHEA diet. All rats were orally gavaged at age 50 days with 65 mg DMBA/kg body weight. Rats were weighed and palpated twice weekly for detection of mammary tumors and sacrificed 155 days post-DMBA treatment. Obese rats fed the DHEA diet gained significantly less weight than obese control diet rats (P<0.001). At the end of the experiment, 55% of the control diet group developed mammary tumors, while no tumors were detected in the DHEA diet group (P<0.001). Our results suggest that DHEA treatment can reduce body weight gain and protects against DMBA-induced mammary tumor development in the obese Zucker rat model.