Final Web Writing Assignment, Retinoblastoma, Luiza
Final Web Writing Assignment Biology 190H 2011
Retinoblastoma (Rb) is cancerous part of the eye that develops in the cells of the retina, the light-detecting tissue of the eye. Fifty-percent of the cancer cases are found as a result of a heritable mutation in a gene controlling cell division, called the Rb gene. If a parent is a carrier of the trait, the offspring has 50% of obtaining that mutation and developing retinoblastoma themselves. The cancer mostly affects children under the age of 6.
When the retinoblastoma gene (Rb) binds with the transcription factor E2F, it becomes a negative regulator of the cell cycle by repressing transcription of genes required for S phase. In a 2007 experiment led by W. Du and J. Pogoriler, studies of Rb family proteins were done on mice. Rb null mice die at their thirteenth embryonic day, and they were observed to find that they had an abnormal S phase and thus neuronal apoptosis was found in the lens and the central nervous system; defects in differentiation of muscles and red blood cells were also found. Rb null mice had unrestrained activity of E2Fs (a removal of any E2F), which caused a defected the S phase in the lens and retina.
Following this experiment, p21/p27 family of cdk inhibitors that play a role in cell cycle regulation, was removed in an Rb +/- background, and the increase in tumor development was found. When either E2F (1) or E2F (3) was removed then there was a decrease in incidences of pituitary tumors while the removal of E2F (3) in Rb +/- mice increased the incidences of thyroid cancer. This connects back to retinoblasts because these reults suggest that in some tumor types the ability of Rb to decrease tumorigenesis is related to the inhibition of the activated E2Fs, which can also be found in the removal of repressed E2F (4).
The results of the experiment with the removal and/or the modification of the Rb gene and the E2F in mice suggest that the Rb and E2F family members are directed not maily by their biochemical activities but under specific mutations, such as the removal of the p21/p27 family. Yet, null mice develop normally despite the removal of p107 or p130 which makes the 0107/p130 null mice not workable because the have defects in chondrocyptes which leads to bone abnormalities. Though rarely found to be mutated in tumors, p107/p130 play a role in tumor suppression. The experiment decreased the observed mice with loss of p107 and recorded that in Rb-/- chimaeric mice, it was enough for them to develop retinoblastomas. The greatest finding was that Rb-/- and p130-/- mice portrayed consistent development of retinoblastomas, suggesting that p130 is particularly important in restraining tumor development in the retina tissues.
A retinoblastoma can either affect one or both eyes. The pupil appears white or may have white spots. Treatment of retinoblastoma’s depend on the size and location of the tumor. Small tumors can be treated with either cryotherapy and laser surgery while radiation is used for larger tumors, and finally , chemotherapy is used when the tumor has spread beyond the eye. In the most extraneous circumstances, the eye is removed (eucleation) is necessary.
Pogoriler, J., and W. Du. "Oncogene - Retinoblastoma Family Genes." Nature Publishing Group : Science Journals, Jobs, and Information. Oncogene. Web. 08 Dec. 2011. .