Retaining the long-survive capacity of Circulating Tumor Cells (CTCs) followed by xeno-transplantation: not only from metastatic cancer of the breast but also of prostate cancer patients.

Elisabetta Rossi,Stefania De Faveri,Marco Pizzi,Umberto Basso,Mariangela Manicone,Vito Barbieri,Giorgia Nardo,Rita Zamarchi,Alberto Amadori,Massimo Rugge,Antonella Facchinetti,Maria Chiara Scaini

doi:10.18632/oncoscience.8

Abstract

We investigated whether Circulating Tumor Cells (CTCs) isolated from epithelial tumors could survive and grow in xenotransplants. To this purpose, EpCAM-positive CTCs were enriched by CellSearch platform the only FDA-cleared automated platform that quantifies tumor burden in peripheral blood and provides clinical evidence of predictive and prognostic value. The CTCs were isolated from metastatic prostate (n=6) and breast (n=2) cancer patients. The xenograft assay was developed in 8-week-old NOD/SCID mice that were subcutaneously injected with increasing amounts of CTCs (ranging from 50 to 3000). Human CTCs were found in 8 out of 8 murine peripheral blood (muPB) and in 6 out of 8 murine bone marrow (muBM) samples, after a median follow-up of 10.3 months. Six out of 8 spleens were positive for human cytokeratin. Our assay showed higher successful rate than those previously reported in breast cancer and hepatocellular carcinoma. The role of EpCAM during carcinogenesis is controversial. The identification of human CTCs in muPB, muBM and spleen demonstrates that the EpCAM-positive fraction of CTCs retains the migratory capacity. This is the first experimental evidence that as few as 50 EpCAM-positive prostate cancer CTCs putatively contain metastasis-initiating-cells (MIC).

Highlights

The presence of epithelial tumor cells in peripheral blood (PB) of cancer patients has been longtime associated with metastasis development [1, 2]
Age-matched control mice (n=6) were processed in parallel and revealed no presence of human Circulating Tumor Cells (CTCs) by IHC analyses. This is the first report showing that EpCAM-positive CTCs isolated from prostate cancer patients are able to initiate metastasis in a xenograft assay [18]
This study is consistent with recent reports on xenografts derived from breast cancer [19] and hepatocellular carcinoma (HCC) CTCs [20], providing the proof of principle about the metastatic potential of EpCAM-positive CTCs

Summary

INTRODUCTION

The presence of epithelial tumor cells in peripheral blood (PB) of cancer patients has been longtime associated with metastasis development [1, 2]. A still open question that raises doubts about the metastatic potential of CTCs is their high grade of apoptosis [13, 14] To address these questions, we investigated whether CTCs isolated ex vivo from metastatic prostate and breast cancer patients were able to grow in NOD/SCID mice, subcutaneously (s.c.) injected with an increasing amount of cells (ranging from 50 to 3000). In order to estimate the apoptotic fraction present in the injected cells, we tested the CTCs for M30 expression, as previously reported [13] This is the first report showing that even as few as 50 EpCAM-positive live CTCs from metastatic prostate cancer patients can survive and grow in a xenograft assay, putatively containing metastasis-initiating-cells (MIC)

RESULTS

DISCUSSION

Findings

Study design