Embryo Implantation and Tumor Metastasis: Common Pathways of Invasion and Angiogenesis

Abstract

Implantation of the embryo is one of the last great mysteries of reproductive biology. There are striking similarities present between the behavior of invasive placental cells and that of invasive cancer cells. In this review, we propose that cellular mechanisms used by the cells of the placenta during implantation are reused by cancer cells to invade and spread within the body. Integrins and other cell adhesion molecules, extracellular matrix and matrix metalloproteinases all appear to be involved and are regulated by the complex endocrine, autocrine and paracrine milieu within the uterus. Angiogenesis is a common feature of both implantation and cancer spread. Endothelial cells also use similar cellular mechanisms during angiogenesis to digest the surrounding matrix, migrate and form new blood vessels. A better understanding of the mechanism of trophoblast invasion will likely lead to insights of various diseases of pregnancy such as preeclampsia. An appreciation of the maternal mechanisms to control this invasive behavior may likewise lead to a better understanding of metastatic cancer cells and lead to better methods to control their growth and spread within host tissues.

MICA triggering signal for NK cell tumor lysis is counteracted by HLA‐G1‐mediated inhibitory signal

“…Moreover, trophoblast cells are similar to tumor cells in terms of proliferative potential and host tissue invasion, specific expression of growth factors, cytokines, oncogenes and antigens. 65 Our results show that no MICA expression could be observed on freshly isolated HLA-G-positive cytotrophoblast cells. In addition to the signal mediated by HLA-G, which may inhibit the lytic activity of decidual NK cells bearing HLA-G-specific KIRs such as p49, 43 the failure to detect an NK activating signal such as MICA on cytotrophoblasts may contribute to immune privilege for the fetus.…”

Targeting Protein Kinase C: New Therapeutic Opportunities Against High-Grade Malignant Gliomas?

“…Notably, such processes are not restricted to neoplastic cells, but are physiological events inherent to normal cells, occurring, for instance, during trophoblast implantation, involution of the mammary gland, embryological morphogenesis, as well as tissue remodeling [154,155]. Tumor cell invasion is a pathological process that results from loss of control over these functions.…”

An Alternative Role of C1q in Cell Migration and Tissue Remodeling: Contribution to Trophoblast Invasion and Placental Development

“…Some of the invading trophoblast cells penetrate the spiral arteries and migrate upward against blood flow, forming intravascular islands and mosaic vessels as a result of partial replacement of the endothelium (2,3). Trophoblast cells share with tumor cells the ability to invade tissues, with the major difference that trophoblast invasion is a physiological event strictly restricted to pregnancy and spatially limited to the decidual microenvironment (4)(5)(6)(7). Impairment of this process results in pathological conditions associated with pregnancy including intrauterine growth restriction and pre-eclampsia (8,9).…”