One deadly scourge may lead to cures for another.

A genetically modified form of the HIV virus was used by scientists at the University of Pennsylvania to re-program cancer patients' own immune systems to attack cancer cells.

BLOG: Phosphorescent Felines Fight AIDS

The treatment seems to have knocked out cancer in two patients and weakened it in a third. All three suffered from chronic lymphocytic leukemia, but researchers believe the technique could be adapted to take down other forms of cancer.

The technique was recently published in the New England Journal of Medicine. It works like this:

1. Doctors run the patients blood through a machine that removes T-cells, but returns the rest of the blood to the patient. T-cells are virus and cancer fighting white blood cells.

2. A modified form of the HIV virus is used to infect the T-cells and insert genes that cause it to recognize and attack a particular cancer, then multiply and survive in the patients for months.

The modified HIV virus carries what Carl June, one of the doctors involved, called a "Rube Goldberg-like solution," in an interview with the New York Times. The virus carries DNA from humans, mice and cows, a virus that infects woodchucks, and one that infects cows.

The modified T-cells then carry chimeric antigen receptors, proteins which allow them to recognize and kill multiple cancer cells.

3. Chemotherapy kills any remaining T-cells in the patient. The doctors don't want un-modified T-cells impeding the new ones.

4. The modified T-cells are returned to the patient. Within the patient the newly re-programmed T-cells proliferate.

"The patient becomes a bioreactor," said June.

5. Over the next few weeks the patient develops a temperature, chills, shakes, low blood pressure, and other flu-like symptoms. The symptoms are caused by chemicals called cytokines produced by the T-cells.

The flu-like symptoms also mean the cancer is on the run. After the ordeal, doctors estimated that two pounds of cancer cells had died off in one patient, William Ludwig.

"I have my life back," Ludwig said in a New York Times article.

Six months after treatment Ludwig's cancer was still in remision and he still had the modified T-cells in his blood stream, ready to fight a resurgence of the leukemia.

BLOG: How Broccoli Fights Cancer

Another patient received a far smaller dose of T-cells, but his cancer also went into remission.

The third patient was treated with steroids at another hospital after the flu-like symptoms kicked in. He only experienced a partial remission, possibly due to the steroids, or to more advanced stage of his cancer.

The University of Pennsylvania doctors plan to use the technique on other forms of cancer, including deadly, hard to treat forms like mesothelioma, ovarian, and pancreatic cancer.