Cancer is a worldwide problem that afflicts millions of people each year. As such, finding new methods of treatments is of vital interest. Both chemotherapy and radiation therapy are used in the treatment of cancer. Radiation treatment has become a conventional part of cancer therapy and is used in approximately 60% of treatment regimens. The cytotoxic effect of radiation on cancer cells arises from the ability of radiation to cause breaks in one or both strands of the DNA molecules inside the cells. Cells in all phases of the cell cycle are susceptible to this effect. However, the DNA damage in cancer cells is more likely to be lethal because these cells are less capable of repairing their DNA. The side effects of radiation are similar to those of chemotherapy and occur for the same reason i.e., the damage of healthy cells and tissue. Thus, a shortcoming to radiotherapy is the destruction of normal, healthy tissue surrounding the tumor during treatment. Another shortcoming is that after cessation of treatment, recurrence of the tumor can and does occur. Recurrence of the tumor has been partly attributed to the presence of radioresistant hypoxic cells, and the enhancement of radiation doses to damage the hypoxic tumor tissue is often necessary. However, to save normal, healthy tissue, a reduction in the total radiation dose would be desirable. Obviously, these two factors are contradictory. Therefore, the use of certain drugs and chemicals that preferentially sensitize hypoxic tumor cells to radiation, radiosensitizers, are employed. Radiosensitizers normally are chemical agents that have the capacity to increase the lethal effects of radiation when administered in conjunction with radiation and there are a variety of radiosensitizers that act by more than one mechanism. Furthermore, in the treatment of cancer with radiation and chemotherapy, local tumor control is often improved when radiation is administered synchronously with the chemotherapeutic agent (21). This observation has been attributed to a super additive effect on tumor regression due to a synergistic interaction between the radiation and the drug. Nevertheless, despite the above improvements in cancer treatment, cancer remains difficult to treat and cells still become resistant to radiation therapy.
Thus, alternative methods and compositions which will increase the sensitivity of cancer cells to radiation therapy, thereby allowing for less exposure to toxic chemotherapeutic agents and radiation therapy, reduced side-effects and improved beneficial results, are still desirable. The present invention seeks to meet these and other needs.
The present description refers to a number of documents, the content of which is incorporated by reference in their entirety.