A study published in Nature (2008) identifies endogenous human microRNAs that suppress breast cancer metastasis. The research focuses on microRNAs (miRNAs) whose expression is lost as human breast cancer cells develop metastatic potential. The study shows that restoring the expression of these miRNAs in malignant cells suppresses lung and bone metastasis in vivo. Specifically, miR-126 reduces overall tumour growth and proliferation, while miR-335 inhibits metastatic cell invasion. miR-335 regulates a set of genes whose collective expression in human tumours is associated with the risk of distal metastasis. miR-335 suppresses metastasis and migration by targeting the progenitor cell transcription factor SOX4 and the extracellular matrix component tenascin C. The loss of miR-335 and miR-126 expression in primary breast tumours from patients who relapse is associated with poor distal metastasis-free survival. The study identifies miR-335 and miR-126 as metastasis suppressor microRNAs in human breast cancer. The study highlights the role of miRNAs as upstream regulators of metastatic progression, as they can post-transcriptionally regulate entire sets of genes. The research identifies miR-335, miR-126, and miR-206 as miRNAs that suppress metastasis in breast cancer cells. miR-335 and miR-126 are expressed in normal human breast tissue and their loss in tumours is associated with metastatic relapse. The study also identifies SOX4 and tenascin C as in vivo mediators of metastasis, with miR-335 directly targeting these genes. The findings suggest that miRNAs can function as suppressors of metastasis, and that their expression is inversely associated with metastatic relapse in breast cancer. The study also shows that miR-335 regulates a set of genes that are directly associated with relapse, and that the loss of miR-335 and miR-126 expression is linked to poor metastasis-free survival. The study provides evidence that miRNAs can serve as clinically meaningful suppressors of metastasis, and that their expression is important for maintaining normal tissue integrity. The findings have implications for the prognosis of breast cancer patients, as miR-335 and miR-126 may be used as prognostic markers.A study published in Nature (2008) identifies endogenous human microRNAs that suppress breast cancer metastasis. The research focuses on microRNAs (miRNAs) whose expression is lost as human breast cancer cells develop metastatic potential. The study shows that restoring the expression of these miRNAs in malignant cells suppresses lung and bone metastasis in vivo. Specifically, miR-126 reduces overall tumour growth and proliferation, while miR-335 inhibits metastatic cell invasion. miR-335 regulates a set of genes whose collective expression in human tumours is associated with the risk of distal metastasis. miR-335 suppresses metastasis and migration by targeting the progenitor cell transcription factor SOX4 and the extracellular matrix component tenascin C. The loss of miR-335 and miR-126 expression in primary breast tumours from patients who relapse is associated with poor distal metastasis-free survival. The study identifies miR-335 and miR-126 as metastasis suppressor microRNAs in human breast cancer. The study highlights the role of miRNAs as upstream regulators of metastatic progression, as they can post-transcriptionally regulate entire sets of genes. The research identifies miR-335, miR-126, and miR-206 as miRNAs that suppress metastasis in breast cancer cells. miR-335 and miR-126 are expressed in normal human breast tissue and their loss in tumours is associated with metastatic relapse. The study also identifies SOX4 and tenascin C as in vivo mediators of metastasis, with miR-335 directly targeting these genes. The findings suggest that miRNAs can function as suppressors of metastasis, and that their expression is inversely associated with metastatic relapse in breast cancer. The study also shows that miR-335 regulates a set of genes that are directly associated with relapse, and that the loss of miR-335 and miR-126 expression is linked to poor metastasis-free survival. The study provides evidence that miRNAs can serve as clinically meaningful suppressors of metastasis, and that their expression is important for maintaining normal tissue integrity. The findings have implications for the prognosis of breast cancer patients, as miR-335 and miR-126 may be used as prognostic markers.