Before I get into evaluating the next stock, I thought I’d start a new intermittent series called Back to the Basics. If you have a degree in biology, this is may bore you a little, but I promise, they won’t all be this basic and feel free to throw your two cents in the comments. As a side benefit of reading this post, you’ll get to find out which stock I’m going to review next.

The building blocks of cells looks like this:

DNA—–>RNA—->Proteins

It’s a pretty linear process with potential for feedback to regulate the expression of the protein. I’ll break down each one briefly and talk about drugs that are made from them and drugs that affect each one.

DNA

DNA encodes our genes. In the large scheme of things, DNA doesn’t really do anything. It just sits there and gets transcribed (see RNA below). Mutations in genes often result in cancer. Mutations can be inherited, but they can also occur spontaneously.

Drugs that affect DNA:

• Some chemotheraputic agents (anti-cancer drugs) like cisplatin damage the DNA in an attempt to kill the cancer cells

• Drugs like dacarbazine/DTIC inhibit DNA replication (making copies of itself), thus preventing cancer cells from dividing.

Drugs that are made of DNA:

• In order to alleviate the protein instability problem (see below), many attempts have been made to make DNA drugs. The DNA enters the cell and is then made into proteins by the cells (gene therapy). I don’t think that any have been given FDA approval, but please correct me if there’s ones I’m unaware of.

RNA

The DNA is transcribed into messenger RNA. There are some RNAs that do actually perform functions in combination with proteins, but the majority of RNAs don’t really do anything. This step of the building blocks is basically a regulatory step. The transcription levels of any particular gene can be tightly regulated and this how cells end up having different functions. The muscle cells transcribe genes for structural proteins while immune cells transcribe genes that encode for proteins that help fight infections. There are certainly other places that a cell can regulate protein levels, but it usually starts at the RNA level.

Drugs that affect RNA:

• Antibiotics often inhibit the transcription of RNA in bacteria. Since the transcription machinery is different in bacteria, the drugs are designed to bind to the bacterial transcription machinery, but don’t affect our cells.

Drugs that are made of RNA:

• Rosetta Genomics, the subject of the next stock I’ll be reviewing, is partnering with companies looking for microRNAs theraputic treatments of liver cancer and virus based infectious diseases.

Proteins

So the messenger RNA in the last section encodes for proteins. Scientists call this process translation. You shouldn’t think of proteins in the same way as proteins that you eat. Those are mostly structural proteins in muscle cells, but proteins do so much more. Most of the interesting proteins are enzymes that catalyze reactions in the cells; for instance, proteins are responsible for the steps of transcription and translation. Proteins are also responsible for regulating the levels of nutrients in the cells (membrane channels). Other proteins move between cells and act as signaling molecules (growth factors).

Drugs that affect proteins:

• This would be a majority of the drugs on the market so I’m not going to list them all. The basic idea, is you design a small molecule that will bind to a protein and inhibit it’s function. By inhibiting it’s function you can turn off a pathway (for instance, one that is promoting tumor growth). Its also possible to find a molecule that makes a protein constitutively active, thus stimulating the pathway. Alternatively, if you inhibit an inhibitor of a pathway, you can actually stimulate that pathway.

Drugs that are proteins:

• This would be a ton too. Sometimes the protein is an antibody which binds a protein and inhibits it’s function. Other times the protein is itself active and the drug’s purpose is to get more of the protein into the cells so that the pathway it affects is activated. In general, small molecules make much better drugs than proteins because they are more stable in the body.

Clear as mud? Feel free to ask questions in the comments. You might spawn another post in this series or if it’s a quick answer, look for the reply in the comments.

Filed under: Back to the Basics