tirapazamine and Colorectal-Neoplasms

To assess the contribution of hypoxia and bone marrow-derived cells to aggressive outgrowth of micrometastases after liver surgery.. Liver surgery generates a microenvironment that fosters aggressive tumor recurrence. These areas are characterized by chronic hypoxia and influx of bone marrow-derived cells.. The contribution of hematopoietic cell types was studied in mice lacking specific components of the immune system and in irradiated mice lacking all bone marrow-derived cells. Tumor cells were derived from colorectal cancer patients and from a metastatic tumor cell line. Hypoxia-induced changes in stem cell and differentiation marker expression, clone-forming potential, and metastatic capacity were assessed. The effect of vascular clamping on cancer stem cell (CSC) characteristics was performed in mice bearing patient-derived liver metastases.. Immune cells and bone marrow-derived cells were not required for aggressive outgrowth of micrometastases in livers treated with surgery. Rather, hypoxia was sufficient to promote invasion and accelerate metastatic outgrowth. This was associated with a rapid loss of differentiation markers and increased expression of CSC markers and clone-forming capacity. Likewise, metastases residing in ischemia-reperfusion-injured liver lobes acquired CSC characteristics. Despite their renowned general resistance to chemotherapy, clone-forming CSCs were readily killed by the hypoxia-activated prodrug tirapazamine.. Surgery-generated hypoxia in the liver causes rapid dedifferentiation of tumor cells into immature CSCs with high clone- and metastasis-forming capacity. The results help explain the phenomenon of aggressive local tumor recurrence after liver surgery and offer a potential strategy to kill aggressive CSCs by hypoxia-activated prodrugs.

Topics: Animals; Antineoplastic Agents; Biomarkers, Tumor; Blotting, Western; Catheter Ablation; Cell Line, Tumor; Colorectal Neoplasms; Flow Cytometry; Hematopoietic Stem Cells; Hepatectomy; Humans; Hypoxia; Immunohistochemistry; Liver Neoplasms, Experimental; Male; Mice; Mice, Inbred BALB C; Mice, Inbred NOD; Mice, Nude; Mice, SCID; Neoplasm Invasiveness; Neoplasm Micrometastasis; Neoplasm Recurrence, Local; Neoplasm, Residual; Neoplastic Stem Cells; Phenotype; Postoperative Complications; Real-Time Polymerase Chain Reaction; Reperfusion Injury; Tirapazamine; Triazines

Radiofrequency ablation (RFA) is a common procedure for the management of colorectal liver metastases. RFA-generated lesions are surrounded by a rim of hypoxia that is associated with aggressive outgrowth of intrahepatic micrometastases. Hypoxia-activated prodrugs such as tirapazamine are designed selectively to induce apoptosis in tumour cells under hypoxic conditions. Therefore, it was hypothesized that tirapazamine may have therapeutic value in limiting hypoxia-associated tumour outgrowth following RFA.. Murine C26 and MC38 colorectal cancer cells were grown under hypoxia and normal oxygenation in vitro, and treated with different concentrations of tirapazamine. Apoptosis and cell cycle distribution were assessed by western blot and fluorescence-activated cell sorting analysis. Proliferative capacity was tested by means of colony-formation assays. Mice harbouring microscopic colorectal liver metastases were treated with RFA, followed by a single injection of tirapazamine (60 mg/kg) or saline. Tumour load was assessed morphometrically 7 days later.. Tirapazamine induced apoptosis of colorectal tumour cells under hypoxia in vitro. Under normal oxygenation, tirapazamine caused a G2 cell cycle arrest from which cells recovered partly. This reduced, but did not abolish, colony-forming capacity. A single dose of tirapazamine largely prevented accelerated outgrowth of hypoxic micrometastases following RFA. Tirapazamine administration was associated with minimal toxicity.. Tirapazamine induced apoptosis in colorectal cancer cells in a hypoxia-dependent manner and potently suppressed hypoxia-associated outgrowth of liver metastases with limited toxicity. This warrants further study to assess the potential value of tirapazamine, or other hypoxia-activated prodrugs, as adjuvant therapeutics following RFA treatment of colorectal liver metastases.

Topics: Animals; Antineoplastic Agents; Apoptosis; Blotting, Western; Catheter Ablation; Cell Hypoxia; Colorectal Neoplasms; Flow Cytometry; Liver Neoplasms; Liver Neoplasms, Experimental; Male; Mice; Mice, Inbred BALB C; Neoplasm Transplantation; Prodrugs; Tirapazamine; Triazines; Tumor Cells, Cultured

Topics: Animals; Antineoplastic Agents; Catheter Ablation; Colorectal Neoplasms; Liver Neoplasms; Male; Prodrugs; Tirapazamine; Triazines