Raft-dependent endocytosis of autocrine motility factor/phosphoglucose isomerase: a potential drug delivery route for tumor cells.

Abstract

BACKGROUND:

Autocrine motility factor/phosphoglucose isomerase (AMF/PGI) is the extracellular ligand for the gp78/AMFR receptor overexpressed in a variety of human cancers. We showed previously that raft-dependent internalization of AMF/PGI is elevated in metastatic MDA-435 cells, but not metastatic, caveolin-1-expressing MDA-231 cells, relative to non-metastatic MCF7 and dysplastic MCF10A cells suggesting that it might represent a tumor cell-specific endocytic pathway.

METHODOLOGY/PRINCIPAL FINDINGS:

Similarly, using flow cytometry, we demonstrate that raft-dependent endocytosis of AMF/PGI is increased in metastatic HT29 cancer cells expressing low levels of caveolin-1 relative to metastatic, caveolin-1-expressing, HCT116 colon cells and non-metastatic Caco-2 cells. Therefore, we exploited the raft-dependent internalization of AMF/PGI as a potential tumor-cell specific targeting mechanism. We synthesized an AMF/PGI-paclitaxel conjugate and found it to be as efficient as free paclitaxel in inducing cytotoxicity and apoptosis in tumor cells that readily internalize AMF/PGI compared to tumor cells that poorly internalize AMF/PGI. Murine K1735-M1 and B16-F1 melanoma cells internalize FITC-conjugated AMF/PGI and are acutely sensitive to AMF/PGI-paclitaxel mediated cytotoxicity in vitro. Moreover, following in vivo intratumoral injection, FITC-conjugated AMF/PGI is internalized in K1735-M1 tumors. Intratumoral injection of AMF/PGI-paclitaxel induced significantly higher tumor regression compared to free paclitaxel, even in B16-F1 cells, known to be resistant to taxol treatment. Treatment with AMF/PGI-paclitaxel significantly prolonged the median survival time of tumor bearing mice. Free AMF/PGI exhibited a pro-survival role, reducing the cytotoxic effect of both AMF/PGI-paclitaxel and free paclitaxel suggesting that AMF/PGI-paclitaxel targets a pathway associated with resistance to chemotherapeutic agents. AMF/PGI-FITC uptake by normal murine spleen and thymus cells was negligible both in vitro and following intravenous injection in vivo where AMF/PGI-FITC was selectively internalized by subcutaneous B16-F1 tumor cells.

CONCLUSIONS/SIGNIFICANCE:

The raft-dependent endocytosis of AMF/PGI may therefore represent a tumor cell specific endocytic pathway of potential value for drug delivery to tumor cells.

• Authors: Liliana D Kojic, Sam M Wiseman, Fariba Ghaidi, Bharat Joshi, Hinyu Nedev, H Uri Saragovi, Ivan R Nabi
• Journal: PloS one (PLoS One) Vol. 3 Issue 10 Pg. e3597 ( 2008) ISSN: 1932-6203 [Electronic] United States
• PMID: 18974847 (Publication Type: Evaluation Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Receptors, Cytokine
• AMFR protein, human
• Amfr protein, mouse
• Receptors, Autocrine Motility Factor
• Ubiquitin-Protein Ligases
• Glucose-6-Phosphate Isomerase
• Paclitaxel

Topics

• Animals
• Antineoplastic Agents (administration & dosage)
• Caco-2 Cells
• Carcinoma (metabolism, pathology)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Colonic Neoplasms (metabolism, pathology)
• Drug Delivery Systems (methods)
• Endocytosis (physiology)
• Glucose-6-Phosphate Isomerase (metabolism)
• HCT116 Cells
• HT29 Cells
• Humans
• Melanoma (metabolism, pathology)
• Membrane Microdomains (metabolism, physiology)
• Mice
• Neoplasms (drug therapy, metabolism)
• Paclitaxel (administration & dosage, chemistry)
• Receptors, Autocrine Motility Factor
• Receptors, Cytokine (metabolism)
• Ubiquitin-Protein Ligases (metabolism)