The study of circulating tumor cells (CTCs) has rapidly increased in the last decade, as this entity of cells is implicated in cancer prognosis and progression. CTCs constitute a non-homogeneous population of cells, with metastatic ability. The present study tested the gene expression profile of genes involved in metastasis in particular organs, in CTCs from cancer patients representing different cancer types and stages.
Blood samples were randomly collected from 35 patients, suffering from breast, prostate, ovarian, lung, colorectal, peritoneal, bladder, endometrial and stomach cancer. CTCs were isolated using enrichment protocols and cellular-molecular based assays were used to enumerate and study their expression profiles. qRT-QPCR for genes correlated with risk metastasis in principle (TGFBR2, ITGB5, ITGB6), risk of metastasis to pleura (CCR6), skin (CCR7), lung (IGF2R, ERK1, ERK2), bone (BMPR1A, BMPR1B, BMPR2, CXCR4, BST2), liver (CXCR4, TRAILR2, FAS, MET) and brain metastasis (STAT3, CX3CR1, DSC2) performed by using ACTB as housekeeping gene. All the reactions were performed in triplicates. A normal and a reference cancer RNA was used as control.
Samples mainly from prostate, breast and squamous cancer overexpressed markers involved in general metastasis. These samples were at stage III and IV, and CTCs were 6.7±2.35/ml. For pleura and skin, overexpression was observed in samples with higher CTCs number (8.2±1.3/ml) than in prostate and ovarian cancer, respectively. Markers correlated with liver metastasis were expressed higher in breast and ovarian samples at stage IV. The majority of breast and prostate cancer samples also expressed markers correlated with bone metastasis, while squamous and ovarian cancer samples expressed genes involved in brain metastasis. By contrast, samples with lower CTCs exhibited expression in markers correlated with metastasis to lung (5.8±2.3/ml), involving breast, prostate and ovarian cancer.
Among same cancer type samples, different metastasis profiles were revealed, demonstrating that analysis of CTCs and particularly, their enumeration in comparison with their expression profile might be useful to focus the follow up and screening to specific organs.
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Research Genetic Cancer Centre Group Ethic Committee.
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All authors have declared no conflicts of interest.