Scientists at Institute for Research in Biomedicine (IRB) Barcelona have discovered that some brain tumors in larvae of the fruit fly Drosophila melanogaster use the genetic program of germline cells to grow. The removal of some of these genes leads to healthy brains. This finding demonstrates that these genes are crucial for tumor development. The study was headed by Catalan Institution for Research and Advanced Studies (ICREA) researcher Cayetano González.
One of the characteristics of tumor cells is their immortality, a property that allows them to divide without obeying external signals. As a result, tissue masses form, which, in most cases, interfere with organ functions. Data collected in recent years reveal that many human tumors activate specific genes of the germinal cell line – those specialized in spermatozoids or ovules - which is thought to allow them greater and longer viability. However, the role of these genes in tumor development remains to be established. In this study, the scientists showed for the first time that silencing some of these genes leads to the disappearance of tumors in the brain of the fruit fly.
Global analysis of gene expression in tumors
Not all cells use the same genes, but they make use of them depending on the function to be performed. This gene activation profile is what determines how cells divide and what they become specialized in, in the case they have not already done so. In this study the researchers have used DNA chip technology to monitor this gene activity in tumor cells and have compared it with healthy cells. For this purpose, they have analyzed brain tumors induced by an alteration in the gene lmbt in fruit fly larvae.
Analysis of the gene expression profiles indicates that these tumor cells activate a total of 102 genes that are not activated in healthy cells. When the researchers examined the functions of these genes they observed that, in many cases, they were unknown, although 25% of them were responsible for functions related to germline cells. “These results show that these tumors mimic the gene expression profiles of germline cells,” explains Ana Janic, first author of the study and a PhD student in González’s lab.
Germline genes contribute to tumor growth
When the scientists studied the possible role of these specific genes of the germinal cell line in tumor expansion, they observed that by the silencing four lead to the development of healthy brains. “These experiments demonstrate that these genes are crucial for the development of this kind of tumor,” states Janic.
Data collected over the last 10 years indicate that the cancer cells of some tumors, such as melanomas and some kinds of carcinoma, activate genes of the germinal cell line. One possible diagnostic approach derived from these studies would be to use some of the proteins produced by these genes as tumor cell markers. In this context, the use of these proteins to make cancer vaccines is of particular relevance. This study sheds new light on the role of these proteins in the pathogenesis of cancer and opens up the way for new lines of research for the development of treatment against this disease in humans.
Illustration: Brain tumors in larvae of the fruit fly Drosophila melanogaster express proteins that are normally expressed in germline cells (in red). (c) IRB Barcelona. C. González.
Institute for Research in Biomedicine Barcelona News (12/23/10)
Science Daily (12/28/10)
Medical News Today (01/02/11)
Abstract (Science; 2010 Dec 24;330(6012):1761-2)