A team of researchers has found that the expression pattern of certain microRNAs, or miRNAs, may predict tumor aggressiveness in some patients with lung cancer. These findings indicate that miRNAs may represent a new class of diagnostic and prognostic tools for lung cancer. The study is a collaboration among researchers at
The Ohio State University Comprehensive Cancer Center, Columbus, Ohio; the Jikei University School of Medicine, Tokyo, Japan; National Cancer Center Research Institute, Tokyo, Japan; and the Center for Cancer Research at the National Cancer Institute (NCI), which is part of the National Institutes of Health. The study results appear in the March 13, 2006, issue of Cancer Cell.
miRNAs are small segments of genetic material called ribonucleic acid, or RNA, and are thought to control gene expression. Their actions could change the expression of cancer-related genes within a cell and lead to malignancies.
The researchers identified two miRNAs — has-mir-155 and has-let-7a-2 — that could be used as prognostic indicators in patients with adenocarcinoma, a malignancy of the mucous glands in the lungs. High levels of has-mir-155 or low levels of has-let-7a-2 were associated with poor prognosis. Specifically, overexpression of has-mir-155, or the signalling of the miRNA to change the amount of a protein produced, was the most significant indicator of this prognosis, independent of tumor stage. Although these miRNAs have been identified in other cancers, this is the first evidence linking has-mir-155 to lung cancer.
A tumor with an overexpression of has-mir-155 or reduced expression of has-let-7a-2 would indicate the need for aggressive chemotherapy or radiation treatments. Other tumors that do not show high has-mir-155 or low has-let-7a-2 levels are less aggressive, and those patients might not require more therapy.
“This study is significant because it provides another tool for studying prognosis that is independent of tumor stage,” said Curtis Harris, M.D., chief of the Laboratory of Human Carcinogenesis at NCI and co-leader of this study. “Following surgery, 50 to 60 percent of patients with stage I lung cancer will develop metastatic disease within five years. This may indicate that there are micrometastases that have not been detected by imaging, scanning or pathology.” Harris noted that “in the future, we can use miRNAs and other biological predictors to select patients who may need more aggressive treatment versus those who may not. Additional studies confirming these results are the next step before incorporating miRNA analysis into routine clinical practice.”
Lung cancer is the leading cause of death due to cancer and is primarily caused by exposure to tobacco smoke. Scientists seek to better understand the mechanisms underlying this disease, and miRNAs may provide a way to examine the regulation of cancer-related genes.
NCI Media Relations Branch
Message posted by: Rashmi Nemade
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