Nanoparticle-based delivery systems provide new opportunities to overcome the limitations associated with traditional small-molecule drug therapy for cancer and to achieve both therapeutic and diagnostic functions in the same platform. Preclinical trials are generally designed to assess therapeutic potential and not to optimize the design of the delivery platform. Consequently, progress in developing design rules for cancer nanomedicines has been slow, hindering progress in the field. Despite the large number of preclinical trials, several factors restrict comparison and benchmarking of different platforms, including variability in experimental design, reporting of results, and the lack of quantitative data. To solve this problem, we review the variables involved in the design of preclinical trials and propose a protocol for benchmarking that we recommend be included in in vivo preclinical studies of drug-delivery platforms for cancer therapy. This strategy will contribute to building the scientific knowledge base that enables development of design rules and accelerates the translation of new technologies. Cancer Res; 75(19); 1–5. ©2015 AACR.

Nanoparticle-based delivery systems provide new opportunities to overcome the limitations associated with traditional small molecule drug therapy for cancer, and to achieve both therapeutic and diagnostic functions in the same platform. Pre-clinical trials are generally designed to assess therapeutic potential and not to optimize the design of the delivery platform. Consequently, progress in developing design rules for cancer nanomedicines has been slow, hindering progress in the field. Despite the large number of pre-clinical trials, several factors restrict comparison and benchmarking of different platforms, including variability in experimental design, reporting of results, and the lack of quantitative data. To solve this problem, we review the variables involved in the design of pre-clinical trials and propose a protocol for benchmarking that we recommend be included in in vivo pre-clinical studies of drug delivery platforms for cancer therapy. This strategy will contribute to building the scientific knowledge base that enables development of design rules and accelerates the translation of new technologies.

Heparanase is the only enzyme in mammals capable of cleaving heparan sulfate, an activity implicated in tumor inflammation, angiogenesis and metastasis. Heparanase is secreted as a latent enzyme that is internalized and subjected to proteolytic processing and activation in lysosomes. Its role under normal conditions has yet to be understood. Here we provide evidence that heparanase resides within autophagosomes where studies in heparanase-deficient or transgenic mice established its contributions to autophagy. The pro-tumorigenic properties of heparanase were found to be mediated in part by its pro-autophagic function, as demonstrated in tumor xenograft models of human cancer and through use of inhibitors of the lysosome (chloroquine) and heparanase (PG545), both alone and in combination. Notably, heparanase-overexpressing cells were more resistant to stress and chemotherapy in a manner associated with increased autophagy, effects that were reversed by chloroquine treatment. Collectively, our results establish a role for heparanase in modulating autophagy in normal and malignant cells, thereby conferring growth advantages under stress as well as resistance to chemotherapy.

Carbonic anhydrase buffers tissue pH by catalyzing the rapid interconversion of carbon dioxide (CO2) and bicarbonate (HCO3−). We assessed the functional activity of CAIX in two colorectal tumor models, expressing different levels of the enzyme, by measuring the rate of exchange of hyperpolarized 13C label between bicarbonate (H13CO3−) and carbon dioxide (13CO2), following injection of hyperpolarized H13CO3−, using 13C-magnetic resonance spectroscopy (13C-MRS) magnetization transfer measurements. 31P-MRS measurements of the chemical shift of the pH probe, 3-aminopropylphosphonate, and 13C-MRS measurements of the H13CO3−/13CO2 peak intensity ratio showed that CAIX overexpression lowered extracellular pH in these tumors. However, the 13C measurements overestimated pH due to incomplete equilibration of the hyperpolarized 13C label between the H13CO3− and 13CO2 pools. Paradoxically, tumors overexpressing CAIX showed lower enzyme activity using magnetization transfer measurements, which can be explained by the more acidic extracellular pH in these tumors and the decreased activity of the enzyme at low pH. This explanation was confirmed by administration of bicarbonate in the drinking water, which elevated tumor extracellular pH and restored enzyme activity to control levels. These results suggest that CAIX expression is increased in hypoxia to compensate for the decrease in its activity produced by a low extracellular pH and supports the hypothesis that a major function of CAIX is to lower the extracellular pH. Cancer Res; 75(19); 1–10. ©2015 AACR.

Carbonic anhydrase (CA) buffers tissue pH by catalyzing the rapid interconversion of carbon dioxide (CO2) and bicarbonate (HCO3-). We assessed the functional activity of CAIX in two colorectal tumor models, expressing different levels of the enzyme, by measuring the rate of exchange of hyperpolarized 13C label between bicarbonate (H13CO3-) and carbon dioxide (13CO2), following injection of hyperpolarized H13CO3-, using 13C magnetic resonance spectroscopy (13C-MRS) magnetization transfer measurements. 31P-MRS measurements of the chemical shift of the pH probe, 3-aminopropylphosphonate, and 13C-MRS measurements of the H13CO3-/13CO2 peak intensity ratio showed that CAIX overexpression lowered extracellular pH in these tumors. However, the 13C measurements overestimated pH due to incomplete equilibration of the hyperpolarized 13C label between the H13CO3- and 13CO2 pools. Paradoxically, tumors overexpressing CAIX showed lower enzyme activity using magnetization transfer measurements, which can be explained by the more acidic extracellular pH in these tumors and the decreased activity of the enzyme at low pH. This explanation was confirmed by administration of bicarbonate in the drinking water, which elevates tumor extracellular pH and restored enzyme activity to control levels. These results suggest that CAIX expression is increased in hypoxia to compensate for the decrease in its activity produced by a low extracellular pH, and supports the hypothesis that a major function of CAIX is to lower the extracellular pH.