Carbohydrate restriction and lactate transporter inhibition in a mouse xenograft model of human prostate cancer

What's known on the subject? and What does the study add? It is known that both lactate inhibition and carbohydrate restriction inhibit tumour growth. What is unknown is whether the two work synergistically together. This study adds that though the combination of lactate inhibition and carbohydrate restriction did not synergistically slow tumour growth in our model, we confirmed that carbohydrate restriction started after tumour inoculation slowed tumour growth. Moreover, lactate inhibition resulted in changes in the tumour microenvironment that may have implications for future metabolic targeting of prostate cancer growth.

OBJECTIVE

• ? To determine if a no‐carbohydrate ketogenic diet (NCKD) and lactate transporter inhibition can exert a synergistic effect on delaying prostate tumour growth in a xenograft mouse model of human prostate cancer.

MATERIALS AND METHODS

• ? 120 nude athymic male mice (aged 6–8 weeks) were injected s.c. in the flank with 1.0 × 10⁵ LAPC‐4 prostate cancer cells.
• ? Mice were randomized to one of four treatment groups: Western diet (WD, 35% fat, 16% protein, 49% carbohydrate) and vehicle (Veh) treatment; WD and mono‐carboxylate transporter‐1 (MCT1) inhibition via α‐cyano‐4‐hydroxycinnamate (CHC) delivered through a mini osmotic pump; NCKD (84% fat, 16% protein, 0% carbohydrate) plus Veh; or NCKD and MCT1 inhibition.
• ? Mice were fed and weighed three times per week and feed was adjusted to maintain similar body weights.
• ? Tumour size was measured twice weekly and the combined effect of treatment was tested via Kruskal–Wallis analysis of all four groups. Independent effects of treatment (NCKD vs WD and CHC vs Veh) on tumour volume were tested using linear regression analysis.
• ? All mice were killed on Day 53 (conclusion of pump ejection), and serum and tumour sections were analysed for various markers. Again, combined and independent effects of treatment were tested using Kruskal–Wallis and linear regression analysis, respectively.

RESULTS

• ? There were no significant differences in tumour volumes among the four groups (P= 0.09).
• ? When testing the independent effects of treatment, NCKD was significantly associated with lower tumour volumes at the end of the experiment (P= 0.026), while CHC administration was not (P= 0.981). However, CHC was associated with increased necrotic fraction (P < 0.001).

CONCLUSIONS

• ? Differences in tumour volumes were observed only in comparisons between mice fed a NCKD and mice fed a WD.
• ? MCT1 inhibition did not have a significant effect on tumour volume, although it was associated with increased necrotic fraction.

     

On the interaction of rabbit antithrombin III with the luminal surface of the normal and deendothelialized rabbit thoracic aorta in vitro

Pure rabbit antithrombin III was isotope labeled (with 125I or 3H) by two different methods; neither procedure caused a loss of antithrombin activity although both methods affected the affinity of the protein for Sepharose-heparin. From segments from freshly excised rabbit aorta, the uptake of isotope-labeled antithrombin III by the endothelium was rapid and saturable, although relatively small compared to the uptake of thrombin; binding of 3H-antithrombin III to the endothelium resembled that of 125I-antithrombin III. Transendothelial passage of antithrombin III into the subendothelial layers (intima-media) was slow and progressive. Endothelium binding was not affected by pretreating the vessel with either heparin, thrombin, or glycosaminoglycan-specific enzymes. Endothelium-bound antithrombin III was not selectively displaced by either heparin or thrombin. In contrast, endothelium-bound thrombin was rapidly dislodged by antithrombin III as a thrombin- antithrombin III complex. The surface of the deendothelialized aorta (ie, subjected to a balloon catheter) bound antithrombin III avidly. Pretreatment of the deendothelialized vessel with glycosaminoglycan- specific enzymes, particularly heparitinase, decreased intima-media binding by up to 80%. 125I-antithrombin III, when bound to the deendothelialized vessel surface, was actively displaced by either heparin, thrombin, or by unlabeled antithrombin III. The relatively poor binding of antithrombin III compared with that of thrombin by the endothelium in vitro supports an earlier proposal (Lollar P, Owen WG: J Clin Invest 66:1222-1230, 1980) that thrombin bound to high-affinity sites, possibly pericellular proteoglycan, of the endothelium is inactivated by plasma antithrombin III in vivo. Such a situation probably holds for large arteries at least.     

Human platelet fibrinogen: purification and hemostatic properties

Conditions were developed in which 80% to 90% of platelet fibrinogen could be routinely purified in nondegraded form from the fluid phase of platelet suspensions stimulated with the calcium ionophore, A23187, in the presence of calcium, leupeptin, and prostaglandin E1. Fibrinogen was separated from other released proteins by chromatography on diethylaminoethanol (DEAE)-cellulose using a continuous pH and ionic strength gradient. Purified platelet fibrinogen, greater than 98% homogeneous by immunoelectrophoresis and sodium-dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE), consisted of intact A alpha, B beta and gamma A chains, but not gamma' chains, and was 95% to 96% clottable. Platelet fibrinogen was shown to compete for the binding of radiolabeled plasma fibrinogen to ADP-activated platelets in a manner identical to that of unlabeled plasma fibrinogen itself. Also, at equivalent protein concentrations, platelet and plasma fibrinogens supported platelet aggregation to an equivalent extent. Based upon these results, we conclude that there is no significant difference between platelet and plasma fibrinogen with respect to their size, their clottability, their affinity for the activated platelet fibrinogen receptor, or their capacity to support subsequent platelet aggregation.     

Role of Incipient Angiogenesis in Cancer Metastasis

Metastasis is the primary cause of mortality in cancer patients. Angiogenesis is intimately involved in metastasis at the site of entry of tumor cells into the vasculature and at the site of eventual metastasis growth. In this commentary, we review current paradigms regarding angiogenesis in metastatic sites. Recent discoveries challenge some of the existing paradigms.Significant prior data suggest that successful formation of metastases requires: 1) angiogenesis in the primary tumor site; 2) downregulation of cohesive molecules and tumor cell increased motility, resulting in invasion into neovessels; 3) tumor cell embolism; 4) arrest and attachment in capillary beds of distant organs; 5) extravasation and proliferation in the organ parenchyma; and 6) re-establishment of angiogenesis when the tumor reaches >1–2mm in size [1].While most recent data largely confirm the aforementioned sequence of events, a few reports have revealed new knowledge about the earliest phases of angiogenesis of metastases. Of particular importance has been the ability to create tumor cell lines that are stably transfected with reporter genes, such as green fluorescence protein. With these tools it is now literally possible to monitor tumor formation from a single cell [2–7].     

Aminoglycoside-associated hypomagnesaemia in children with cystic fibrosis

Hypomagnesaemia in children with cystic fibrosis (CF) is under-recognized. We report a child with CF who developed significant hypomagnesaemia following intravenous (i.v.) treatment with aminoglycosides for exacerbations of Pseudomonas aeruginosa infection. Three additional cases have also been observed. Investigations in two patients have revealed excessive renal loss of magnesium. It is postulated that renal tubular damage secondary to the cumulative effects of repeated courses of aminoglycosides resulted in hypomagnesaemia, and we suggest screening for this problem by monitoring serum magnesium regularly in all patients with CF receiving multiple courses of aminoglycosides.     

Liver transplant recipients: portable duplex US with correlative angiography

Twenty patients, aged 4 months to 58 years, were evaluated for liver transplantation by duplex sonography, and 15 transplantations were completed; 42 postoperative examinations were performed. Sonographic findings were correlated with seven preoperative and five postoperative angiographic evaluations. Preoperative duplex US findings included tumors, portal vein occlusion, varices, biliary obstruction, and variant vascular anatomy. Postoperative findings included hepatic artery occlusion, portal vein occlusions (one with cavernous transformation), portal vein stenosis, biliary obstruction, intrahepatic and extrahepatic fluid collections, and air in the portal vein due to ischemic bowel. Use of angiography allowed confirmation of the vascular abnormalities and demonstrated evidence of rejection in patients with normal Doppler waveforms. Duplex sonography is a valuable portable technique for evaluating these patients and can be used in triage of patients requiring angiography.     

Synergism between parathyroid hormone and interleukin 1 in stimulating bone resorption in organ culture

The interaction of interleukin 1 (IL-1), a locally produced factor, and parathyroid hormone (PTH), a systemic factor, in stimulating bone resorption was examined using fetal rat long bone organ culture. Concentrations of IL-1 and PTH, which stimulated little bone resorption when present singly, produced marked resorption when present simultaneously. This synergistic interaction of IL-1 and PTH was not affected by the presence of the prostaglandin synthetase inhibitor indomethacin. Both interleukin 1 alpha and interleukin 1 beta were capable of producing synergy. Synergy was not produced by sequential exposure of bone to IL-1 and PTH, but required the simultaneous presence of both mediators. The leftward shift in the dose response curve of PTH produced by IL-1 may be an important mechanism controlling localized bone resorption. A role for IL-1 in stimulating bone resorption in pathologic conditions, such as arthritis and periodontal disease, is strengthened by the finding that even low concentrations of IL-1 can produce resorptive effects by synergistic interaction with PTH.