Question

Explain how the miR-200 family of miRNAs behave as tumorsuppressor genes. What happens when their expression is blocked or decreased?

Short answer

The miR-200 family acts as tumor suppressor genes by inhibiting epithelial-to-mesenchymal transition (EMT), thereby preventing cancer progression. If their expression is blocked or decreased, EMT can occur, leading to cancer progression and metastasis.

Step-by-step solution

Definition of miR-200 family

The miR-200 family of miRNAs are a group of small non-coding RNA molecules that regulate gene expression at the post-transcriptional level. They're particularly known for their role in inhibiting cancer progression and metastasis, which gives them the name 'tumor suppressor genes'.

Role of miR-200 as tumorsuppressor genes

One of the critical roles of the miR-200 family in cancer suppression involves their ability to inhibit epithelial-to-mesenchymal transition (EMT), a key process in the progression of cancers. They do this by targeting ZEB1 and ZEB2, two transcription factors which initiate EMT. By suppressing these factors, miR-200 helps to maintain the epithelial state of the cells, thus preventing cancer progression.

Effects of blocked or decreased expression of miR-200

When the expression of miR-200 genes is blocked or reduced, the inhibition on ZEB1 and ZEB2 is lifted. This lack of regulation permits EMT to take place, converting epithelial cells into a mesenchymal state, a shift that is associated with cancer progression and metastasis. The cells acquire invasive properties, leading to the spread of cancer. Therefore, decreased miR-200 expression is often linked to poor prognosis in cancer patients.