OMG! We've Cured Cancer… (or not)
Australian scientists have developed a “trojan horse” therapy to combat cancer, using a bacterially-derived nano cell to penetrate and disarm the cancer cell before a second nano cell kills it with chemotherapy drugs[…]
Sydney scientists Dr Jennifer MacDiarmid and Dr Himanshu Brahmbhatt, who formed EnGenelC Pty Ltd in 2001, said they had achieved 100 percent survival in mice with human cancer cells by using the “trojan horse” therapy in the past two years.
This is great, 100% survival in mice – We’ve cured cancer! Well, not quite…This technique uses a special delivery vehicle called an EDVs to deliver small interfering RNA (siRNA) to the cancer cells, followed by chemotherapeutic drugs. The siRNA’s are able to turn off specific genes that code for transporters that allow many cancers to pump out the drugs we are trying to use to kill them, and targeting EDV’s directly to the cancer cells allows doctors to use much lower concentrations and presumably avoid a lot of the unpleasant side-effects of chemotherapy.
The idea of using siRNA (and other forms of RNA interference) in therapies is not new. siRNA’s allows scientists to specifically turn off production of practically any protein in a cell, and have been widely used in research to study almost every aspect of cell biology. The difficulty in using siRNA’s in a therapeutic context has been getting them to the right cells, and then getting the siRNA’s inside. Happily, the entry problem seems to be solved with the EDV’s, but targeting the EDV’s to cancer cells alone is a bigger problem.
In this paper, the scientists coated the EDV’s with antibodies that specifically target the cancer cell. Antibodies can be made to target just about any large molecule (called antigens), but unfortunately, cancer cells often look a lot like the non-cancer cells that they were derived from. These scientists were using a cancer model where they already new what the unique tumor antigens were and had antibodies against them. Unfortunately, that situation will not be replicated in many human patients.