Some clarification
Its not the GM crop that is causing the alleged tumours, it is the Roundup, which is a chemical. All the genetic modification does is make the crop resistant to this herbicide, which assists in effective monoculture. Of course, as the DDT and numerous other past experiences tell us, using more Roundup is not necessarily a good thing but is not the genetic modification that is at fault.
Sorry to disagree with you drexciya, but promoter genes, or genetic material in general, will have absolutely no effect on an organism that consumes it. Potentially the promoter could promote the wrong gene, but that is unlikely as resistance markers are used to ensure it is correct.
As with all tech, its not the technology but how it is used. GMOs are used to produce insulin for diabetics as much as for GM crops. We need oversight of its use, not of the tech itself. The ignorance of vocal pressure groups, such as Greenpeace, does nothing but cloud the issue with misinformation.