Radiation-altered genes

Several genetic alterations can influence radiosensitivity of cancer cells and radioresponsive tumors are known to allow more easily radiation-induced apoptosis. Therefore, the proper functioning of the apoptotic machinery regulates radiosensitivity. As described above, a cracial role is played by p53, and its downstream genes p21 and bax, in activating the apoptotic process. Those cancers with mutations at these levels are expected to be radioresistant. 

In the broadest sense, genetic engineering refers to any artificial process that alters the genetic composition of an organism. Such alterations can be carried out indirectly through chemical methods, radiation, or selective breeding. The term usually refers to the process whereby genes or portions of chromosomes are chemically altered. 

Physical. Anecdotal accounts abound of enhanced plant resistance to disease achieved by transient exposure to a wide variety of physical stimuli, e.g., heat, light, microwaves, other electromagnetic radiation, electric current, sound waves, and vibration. In our own laboratory, we have made cucumbers resistant to anthracnose by vibration (Stromberg and Kuc, unpublished). However, these phenomena are poorly understood and may include enhanced resistance resulting from non-specific altered (stress) physiology, nonspecific phytoalexin elicitation, modification of the action of gene products, or sensitization. This interesting but little explored area will not be further discussed in this paper. 

The damages caused by ionizing radiations in nucleic acid and their components are obviously detrimental to the passage of genetic information that requires specific order of intact purine and pyrimidine bases in the DNA strands. Alterations in these bases and the DNA molecules in general can lead to mutations and lethal genes. The disruption of RNA molecules interferes with protein synthesis and can result in eventual cell death. 

Alpha radiation from plutonium produces cytotoxic and genotoxic effects in cultured cells. These can include cell death, chromosomal aberrations (dicentrics, translocations, and complex exchanges), and pretransformation molecular alterations such as upregulation of oncogene products coupled with inactivation of tumor suppressor genes. 

Rakozy C, Grignon DJ, Li Y, et al. p53 gene alteration in prostate cancer after radiation failure and their association with clinical outcome A molecular and immunohistochemical analysis. Pathol Res Pract 1999 195 129-135. 

---