Cancer is a chronic disease, and main reason behind it occurrence has always been unknown. The normal belief is that cancer can be caused due to genetic reasons and various environment factors. The factors responsible for cancer could also be exposure to pollution, poor diet, unhealthy living conditions, and some factors still remain unknown. It is mainly believed that damage of DNA is responsible for changing a normal cell into can cancerous cell. However, it is that DNA damage do occur in body by formation of cancer cells, but it is not likely that only DNA damage can cause a cell to become cancerous cell.