The immune system protects the body against infection caused by bacteria, viruses, fungi or parasites. Normal immne cells are able to monitor mutated cells and remove them before they accumulate and grow into solid tumors. The immune system is important to cancer patients in many ways because

• The cancer can weaken the immune system
• Cancer treatment can weaken the immune system
• The immune system may help to fight your cancer

Cancer cells can secret a number of chemicals which act on immune cells so as to evade immunosurveillance. Also, hematological cancers as well as many cancers which spread into the bone marrow can replace normal cells, leading to compromised immune response. Meanwhile, chemotherapy and radiotherapy can weaken immunity by causing a drop in the number of white blood cells made in the bone marrow.

Some cells of the immune system can recognise cancer cells as abnormal and kill them. therefore, they can be utilized as part of immunotherapy to fight cancers.

A research published on China Pharmacist [2007, 10(12)] reported that protopanaxadiol (PPD) can enhance immune response in addition to it direct inhibitory effect to fight tumor.

Scientists created 3 models of liver cancer, Lewis lung cancer and melanoma on mice, and then gave PPD at 25, 50 and 100 mg/kg for 12 days before measuring lymphocyte responsiveness as well as tumor weight and size. In all three cancer models, PPD at all doses increased the transformation rate of lymphocytes, cytotoxic activity of NK cels as well as interleukin-2 level in a dose-dependent manner, and all 3 parameters were decreased in cyclophosphamide treated mice. In addition to the enhancement of immune response, PPD also dose-dependently inhibited tumor growth, with a maximal inhibition of 43%-50% at 100mg/kg. Though the tumor inhibition by PPD was not comparable with cyclophosphamide, PPD-treated mice maintained a body weight similar to the normal control.

Overall, PPD treatment not only shrank tumor size but also enhanced immune response, and no toxicity was observed in the study. The results are in solid support of PPD’s use in cancer treatment.