How does chemotherapy affect cancer?
Cancer occurs when the cells divide uncontrollably and cannot be stopped by surrounding cells. There are checkpoints during the cell cycle that are broken in cancer cells. Chemo drugs mainly disrupt the cell division and stop the cells from reproducing. There are many ways that chemo drugs can affect cancer cells. One type of chemo drug can bond with the DNA and cause it to break during cell reproduction, causing the cells to die and not being able to divide. Another type of chemo drug can cause the DNA to divide unevenly, therefore making it so that the cell can not divide properly when trying to even out the amount of DNA that is in each cell.
When does Chemotherapy start affecting Cancer cells?
Different chemo drugs can target the cell at different stages during cellular reproduction. Some chemo drugs target the cells during the S phase, or DNA and RNA replication. Others can affect the G phases, where the organelles duplicate and where the cell is checked for DNA equality, and some are not phase specific and can target the cell during any stage in it's life. This is why these types of drugs are the most effective in cancer treatment and the most widely used. The ability to attack the cancer as soon as possible increases the chances of survival for the patient which is very important.
Can cancer grow resistant to chemotherapy? What happens after that?
Cancer cells are almost like normal cells. They can try to fight off anything that will try to harm them and adapt to what is happening. After a period of treatment, cancers can grow and start to fight the effects of the chemo drug that is being used. This is when you hear the doctor tell you that the Chemotherapy "failed." After this happens, the patient is given the option to either switch chemo drugs or use another form of cancer treatment other than chemotherapy. Chemo resistance may occur when a cell that is not killed by the chemo mutates and grows resistance, the cancer cells learn how to repair broken DNA, the proteins that carry the drug across the cell wall could not be functioning properly, etc. There are many reasons why this could happen, scientist are currently trying to develop a way to reduce the chances of chemotherapy resistance.