Circulation times of prostate cancer and hepatocellular carcinoma cells by in vivo flow cytometry

Abstract

In metastasis, the cancer cells that travel through the body are capable of establishing new tumors in locations remote from the site of the original disease. To metastasize, a cancer cell must break away from its tumor and invade either the circulatory or lymphatic system, which will carry it to a new location, and establish itself in the new site. Once in the blood stream, the cancer cells now have access to every portion of the body. Here, we have used the ''in vivo flow cytometer'' to study if there is any relationship between metastatic potential and depletion kinetics of circulating tumor cells. The in vivo flow cytometer has the capability to detect and quantify continuously the number and flow characteristics of fluorescently labelled cells in vivo. We have improved the counting algorithm and measured the depletion kinetics of cancer cells with different metastatic potential. Interestingly, more invasive PC-3 prostate cancer cells are depleted faster from the circulation than LNCaP cells. In addition, we have measured the depletion kinetics of two related human hepatocellular carcinoma (liver cancer) cell lines, high-metastatic HCCLM3 cells, and low-metastatic HepG2 cells. More than 60% HCCLM3 cells are depleted within the first hour. Interestingly, the low-metastatic HepG2 cells possess noticeably slower depletion kinetics. In comparison, \40% HepG2 cells are depleted within the first hour. The differences in depletion kinetics might provide insights into early metastasis processes. ' 2011 International Society for Advancement of Cytometry Key terms in vivo flow cytometer; cancer metastasis; circulating tumor cells; prostate cancer; hepatocellular carcinoma; in vivo confocal imaging METASTASIS is a complicated process that has yet to be completely understood. In metastasis, the cancer cells that travel through the body are capable of establishing new tumors in locations remote from the site of the original disease. To metastasize, a cancer cell must break away from its tumor and invade either the circulatory or lymph system (1-3). Once in the blood stream, the cancer cells now have access to every portion of the body. The cancer cells in the bloodstream must fight the body's defense system and try to reattach itself in a new location. Fewer than 1 in 10,000 cancer cells survive circulation to create a new tumor. The circulation of the blood plays an important role in determining where cancer cells travel. The cancer cells usually are trapped in the first set of capillaries that they encounter downstream from their point of entry. These capillaries are often in the lung, since returning deoxygenated venous blood leaving many organs is returned to the lung for reoxygenation. From the intestines, the blood go to the liver first, thus cancer cells leaving the intestines will go there. Therefore, the lung and the liver are the two most common sites for metastasis in the human body. Many circulating cancer cells cannot finish the entire process of metastasis (4).

Real-Time Monitoring of Rare Circulating Hepatocellular Carcinoma Cells in an Orthotopic Model byIn VivoFlow Cytometry Assesses Resection on Metastasis

“…CTCs might be considered as the seed in recent studies (4)(5)(6)(7)(8)(9)(10)(15)(16)(17)(18). Nevertheless, there are few studies to monitor CTC dynamics under clinically relevant physiologic condition.…”

“…To monitor CTCs, conventional methods usually isolate and count cells expressing epithelial markers from peripheral blood samples (4)(5)(6)(7)(8)(9)(10). However, these methods are restricted by invasiveness, lower sensitivity caused by small blood sample volumes, and difficulty to record the dynamics of CTCs, which in vivo flow cytometry could overcome (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). In vivo flow cytometry is optimized to quantify circulating fluorescently labeled cells in live animals, without the need to extract blood samples.…”

“…In in vivo flow cytometry measurement, when the fluorescent cells in fast flowing blood pass through the laser slit across the artery, the fluorescence signal could be excited and be detected. The technique is capable of monitoring the varieties of target cells in circulation continuously, for example, cancer cells (15,18), hematopoietic stem cells (19,20), lymphocytes (14), and yields quantitative results without affecting the physiology of the subject.…”

“…Previously, the intravenous models have been commonly used in the in vivo flow cytometry measurement of CTCs studies (15,18). In those studies, cancer cells are labeled ex vivo and injected into blood circulation of small animals.…”

Cell counting for in vivo flow cytometry signals with baseline drift

“…Apparently, this \line-gating" method consumes both time and manpower, with a relatively low e±ciency and accuracy, thus it is replaced by the automatic threshold approach combined with a dynamic peak picking procedure. 26 Once the peak reaches beyond the threshold given by a formula, it would be regarded as a cell. This method does not require any control experiments and proves to be an e®ective method in automatic cell peak counting of the IVFC signal.…”