If there were a current TP53 gene therapy clinical trial would you recommend that Lee enroll in it? Why or why not?
s biopsy are in and it ap Show more Part III Gene Expression and Disease Unfortunately the results from Lees biopsy are in and it appears that he has adrenocortical carcinoma (ACC). Fortunately Dr. Aikenhed (who in addition to her clinical practice in the area of oncology also conducts research) is on the cutting edge of developing treatments for this condition. She is part of a consortium of researchers that are trying to catalog all of the different genes that may be involved in adrenal cancer. This will help physicians and scientists to discover drugs to target specific cancer-contributing gene products. Cancer genes can be categorized in many different ways. Proto-oncogenes produce proteins that are involved in promoting the cell cycle. Mutations in these genes tend to cause either an over-production of protein (over-expression) or a protein to be constitutively active (pushing the cell cycle forward even in the absence of a signal to divide (e.g. growth factor)). Tumor suppressor genes on the other hand put the brakes on the cell cycle usually at key checkpoints. Mutations in tumor suppressor genes that contribute to carcinogenesis can cause either abnormally low levels of protein or no functional protein (under-expression) at all. A mutation like this could allow a damaged or rogue cell to divide when it shouldnt. Genome-maintenance genes can also play a role in cancer and they include the telomerase gene (which helps extend the life of a chromosome and consequently the number of cell division cycles that it can undergo) and DNA repair genes (which keep the level of mutations in all genes low). Dr. Aikenhed and her colleagues use microarrays containing the most common genes implicated in ACC to analyze gene expression (both over- or under-expressed genes) in cancer samples compared to normal tissue. To understand more about this technique you decide to review the basics of microarray analysis by going through slides 1-9 at this website: www.hhmi. org/biointeractive/genomics/microarray_analyzing/01.html. It never ceases to amaze you how they can put thousands of tiny pieces of single-stranded DNA on these microarray chips in an organized way creating all sorts of different sequences for samples to hybridize (bind) to. Several microarrays were made with the most common genes implicated in ACC. DNA samples from six patients with ACC were analyzed. Lee F. is Patient #3. The last row represents a control using normal adrenal tissue from a healthy individual. Table 3 Different Genes* Implicated in ACC IGF2 TP53 RAS BCLXL CHRB APC DDB1 MRPL48 EGRF1 CTNNB1 Patient 1 R Y Y Y G R Y Y Y Y Patient 2 R Y Y G Y R Y Y Y Y Patient 3 Y G Y Y Y Y Y Y Y Y Patient 4 Y G Y Y Y R Y Y Y R Patient 5 Y Y R Y Y Y Y Y G Y Patient 6 Y G Y Y G R Y Y Y Y Control Y Y Y Y Y Y Y Y Y Y *gene symbols are consistent with HGNC & OMIM R=red (high expression in diseased compared with normal cells) G=green (low expression in diseased compared with normal cells) Y=yellow (the same expression in both cell types) Questions 1. What can you conclude about gene expression in your patients cells? You decide to search the following World Health Organization website which contains important statistics on this gene: www-p53.iarc.fr/Statistics.html. 2. The most common type of germ line mutation (occurring in ~72% of cases) is a ___________ mutation. 3. Describe how this type of mutation changes the amino acid sequence of a polypeptide made from this gene. Part IV Gene Therapy Despite trying to maintain a professional level of emotional distance you have become attached to Lee and his good natured family. You spend evenings searching the medical literature for potential treatments including clinical trials to help them. You remember learning about gene therapy trials for SCID (Severe Combined ImmunoDeficiency) and LCA (Lebers Congenital Amaurosisa type of hereditary blindness) in the New England Journal of Medicine. Questions 1. How would you describe the main goal of gene therapy to this family? 2. Several different types of viruses including adenoviruses have been used as vectors for gene therapy in humans. Why are viruses used for gene therapy? 3. The two basic types of gene therapy are _________ and _________. What is the main difference between them? 4. Which type would best help this patient and his family? Why? 5. What types of risks/problems are currently associated with gene therapy? You discover that there have been gene therapy trials involving TP53. For a variety of reasons however the treatment has not been approved by the FDA (U.S. Food & Drug Administration) and the trials stalled. The main problem appeared to be that the company developing the treatment did not provide enough evidence to the FDA that the treatment was effective. 6. If there were a current TP53 gene therapy clinical trial would you recommend that Lee enroll in it? Why or why not? Show less
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