TeachableMedicalNews article 07162020

Teachable moment in classrooms:

  1. chemical basis of life – tertiary structure of proteins
  2. cellular basis of life chapter – cell cycle
  3. cellular basis of life chapter – stages of mitosis
  4. reproductive system chapter – structures of the mammary gland

The news item:  Recently a new form of cancer treatment was in the news:

Newer drug extends lives of young breast cancer patients, study finds

The drug Kisqali (ribociclib) is already approved by the FDA, and new research shows it helps some breast cancer patients live longer

The article states that the drug Kisquali extended the survival time of breast cancer patients, and that the drug is a CDK4/6 inhibitor.

So, Why Do I Care??  In the USA alone there will be over 270,000 breast cancer cases in 2020, and it is expected that more than 47,000 breast cancer deaths will happen.  Any improvement in the survival rate over the treatment by traditional chemotherapy is good news.  In addition, attacking breast cancer from a new direction may improve the treatment of other cancers as well.

Plain English, Please!!! First, let’s talk about breast cancer. This cancer is not actually the cancer of the entire breast. Within the breast tissue there is a gland called mammary gland that makes milk in mothers after giving birth. The milk is made in deeper segments of the gland, and several tubes called lactiferous ducts bring the milk to the skin surface. It is the cells of those ducts that develop cancer in most breast cancers.

Second let’s talk about how cancer cells are different from normal cells.  While there are many subtle biochemical differences between normal and cancer cells, the most decisive difference is that cancer cells multiply, divide, uncontrollably. So, most breast cancer develop, because of the cells of the mammary gland ducts divide uncontrollably.

Third, let’s talk about cell division. If cell division is like a drive from one end of the town to the other. The destination of this drive is the creation of two cells from one. When we drive we obey road signs and traffic lights.  Normal cells react to red lights by stopping on the way to cell division. In cancer cells all traffic lights are green, so the cancer cell speeds through town to arrive at the destination. The protein molecules CDK4 and CDK6 are molecular switches of traffic lights for cell division. In normal cells CDK4 and CDK6 turn red lights to green only when needed, and allow cells to proceed to cell division. In cancer cells CDK4 and CDK6 are continuously active.

Third, let’s talk about way this new cancer fighting drug works. CDK4 and CDK6 turns the traffic light green by adding phosphate groups to some proteins. When those proteins have no phosphate attached to them that represents a red light for cell division. The action of adding a phosphate to another protein requires energy, and Kisquali binds to CDK4 and CDK6, and prevents them from receiving energy for the chemical reaction.

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