Metastasis is a complex process that propagates cells from the primary or initial site of the cancer occurrence to
distant parts of the body. Cancer cells break from the cancer site and circulate through the bloodstream or lymph vessels,
allowing them to reach nearly all parts of the body. These circulating tumour cells (CTCs) contain specialized metastasisinitiating
cells (MICs) that reside in the biological heterogeneous primary tumour. Researchers have hypothesized that
metastasis of renal cell carcinoma is initiated by circulation of MICs in patients’ blood and bone marrow. Based on the
cancer stem/progenitor cell concept of carcinogenesis, understanding the molecular phenotypes of metastasis-initiating
cells (MICs) in renal cancer could play a vital role in developing strategies for therapeutic interventions in renal cancer.
Existence of MICs among CTCs in renal carcinoma has not been proven in large scale. However, some studies have
reported that specialized markers are found on the surface of circulating cells from the primary tumour. In mice, MICs
have been isolated from CTCs using such markers, which have then been transplanted into xenograft model to show
whether they give rise to metastasis in different organs. Considering these findings, in this review we have attempted to
summarize the studies connected with MICs and their gene expression profiles that are responsible for metastasis in renal
Keywords: Circulating tumour cells, metastasis-initiating cells, renal cell carcinoma, tumour-initiating cells.
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