The mechanism of cancer metastasis

[URB]

Generally, EMT, Epithelial to Mesenchymal Transitionchanism is thought to be involved in the mechanism in which cancer cells metastasize in the early stage. EMT is an process in which epithelial cells depolarize and lose their cell-to-cell contacts, and gain mesenchymal morphology. The mesenchymal cells is capable of reaching distant sites through blood vessels. So, EMT is thought to a necessary mechanism for metastasis.

 

However, I found a surprising report from Nature Article indicating that EMT isn't required for metastasis.

Kari R. Fischer et al., 2015,Nature. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4662610/

 

They established an EMT lineage-tracing system in mice with the mammary tumors to monitor metastasis of the epithelial cancer cells to lung through EMT using epithelial-specific and mesenchymal-specific markers. This report showed that a small proportion of cancer cells underwent EMT and lung metastasis mainly consisted of epithelial cells which didn't undergo EMT.

 

I think this report is innovative and overthrows the commonly accepted thought that EMT is necessary for metastasis,

However, some questions come to me.

 

How the epithelial cancer cells gain the motility and metastasize without undergoing EMT？

 

How do you think of this report？

 

Please tell me some related reports if you have.

[Endy0816]

Epithelial cells can be found in urine in normal circumstances. Could be purely mechanical seperation going on.

[Xalatan]

Yep I agree with Endy. Metastasis may occur via haematological, lymphoid, or transcoelomic spread. Some of these processes seem like passive processes rather than active motility-based activities - for example being carried via the blood or lymph vessels to the liver or local lymph nodes. The key histological feature may thus be breaking through the protective basement membrane rather than EMT per se - if you look at the definition of carcinoma in situ, it's often defined as a glandular or epithelial tumour being confined to the epithelium or epidermis, since the submucosa or dermis contain the blood and lymph vessels that enable metastatic spread. I guess EMT is one means to break through the basement membrane barrier but not the only.

[Endy0816]

Has me wondering if it ever happens for other cells after injuries.