Antiangiogenesis Targeting Tumor Microenvironment Synergizes Glucuronide Prodrug Antitumor Activity

Abstract

Purpose: This study is aimed at investigating the in vivo antitumor activity of a novel cellimpermeable glucuronide prodrug, 9-aminocamptothecin glucuronide (9ACG), and elucidating the synergistically antitumor effects of antiangiogenesis therapy by targeting the tumor microenvironment. Experimental Design:We analyzed the antitumor effects of 9ACG alone or combined with antiangiogenic monoclonal antibody DC101on human tumor xenografts by measuring tumor growth and mouse survival in BALB/c nu/nu nude and NOD/SCID mice. The drug delivery, immune response, and angiogenesis status in treated tumors were assessed by high performance liquid chromatography, immunohistochemistry, and immunofluorescence assays. Results: We developed a nontoxic and cell-impermeable glucuronide prodrug, 9ACG, which can only be activated by extracellular h-glucuronidase to become severely toxic. 9ACG possesses potent antitumor activity against human tumor xenografts in BALB/c nu/nu nude mice but not for tumors implanted in NOD/SCID mice deficient in macrophages and neutrophils, suggesting that these cells play an important role in activating 9ACG in the tumor microenvironment. Most importantly, antiangiogenic monoclonal antibody DC101 potentiated single-dose 9ACG antitumor activity and prolonged survival of mice bearing resistant human colon tumor xenografts by providing strong h-glucuronidase activity and prodrug delivery through enhancing inflammatory cell infiltration and normalizing tumor vessels in the tumor microenvironment. We also show that inflammatory cells (neutrophils) were highly infiltrated in advanced human colon cancer tissues compared with normal counterparts. Conclusions: Our study provides in vivo evidence that 9ACG has potential for prodrug monotherapy or in combination with antiangiognesis treatment for tumors with infiltration of macrophage or neutrophil inflammatory cells.

PET Imaging of β-Glucuronidase Activity by an Activity-Based 124I-Trapping Probe for the Personalized Glucuronide Prodrug Targeted Therapy

“…bG is considered as a tumor marker (14,15,20) and a prodrug-activating enzyme for cancer prodrug therapies (35,36). Connors and Whisson demonstrated that high bG levels present in plasmacytomas were correlated with higher drug sensitivity of the tumors (37).…”

“…9-11) and gene-directed enzyme prodrug therapy (GDEPT; refs. 6, 12, 13) as well as directly in prodrug monotherapy, which relies on the elevated levels of bG found in the tumor microenvironment (14)(15)(16) to selectively convert prodrug into active drug. For instance, Albin and colleagues reported that the level of bG human breast tumors was up to 6-times greater than that in normal tissues (17).…”

“…Elevated levels of bG present in the tumor environment are believed to be due to tumor overexpression (14) and release from necrotic tumor tissues (19) or tumor-infiltrating immune cells (15). Because bG has been considered as a tumor marker (14,15,20), it would be very useful to image bG activity in vivo to personalize glucuronide prodrug treatment and greatly improve exogenous or endogenous bG-based targeted therapy.…”

Selective Release of a Cyclopamine Glucuronide Prodrug toward Stem-like Cancer Cell Inhibition in Glioblastoma

“…For instance, Juan and colleagues (29) demonstrated that antiangiogenic agents can synergize the antitumor activity of glucuronide prodrugs by selectively enhancing concentration of the activating enzyme in the tumor microenvironment. More recently, the concept of glucuronidase-responsive albumin-binding prodrugs seemed to represent a promising approach to limiting the rapid renal clearance observed with previous glucuronide prodrugs (46).…”

“…In fact, several studies have shown that glucuronide prodrugs can be activated by b-glucuronidase present in high concentrations in necrotic areas of most solid tumors, including glioblastomas (27). b-Glucuronidase is secreted extracellularly in tumors by inflammatory cells such as neutrophils and macrophages, while in healthy tissues, its activity is confined to lysosomes (28,29). This enzymatic specificity of the tumor microenvironment allows glucuronide prodrugs to discriminate between malignant and normal tissues.…”