Dr. Singh.  They have several theories...
Šrīla Prabhupāda.  Suppose you know the cause of cancer. What is the benefit? Even if you could stop cancer, you could not make a man live forever. That is not possible. Cancer or no cancer, a man has to die. He cannot stop death. Death may be caused, if not by cancer, simply by an accident. Real scientific research should aim at stopping death. That is real science, and that is Kṛṣṇa consciousness. Simply to discover some medicine to cure disease is not a triumph. The real triumph is to stop  all  disease.  Bhagavad-gītā  (8.16) asserts that the real trouble is birth, death, old age and disease.  Ābrahma-bhuvanāl lokāḥ punar āvartino 'rjuna : "From the highest planet in the material world down to the lowest, all are places of misery wherein repeated birth and death take place." The solution to the problem of repeated birth and death is Kṛṣṇa consciousness, which we are practicing and offering to everyone. The perfect result of this practice is that after the present body becomes useless and dies, one is no longer forced to accept a material body subject to birth, death, disease and old age. This is  real  science.