Question

You believe protein D is involved in the metastatic process. Describe experiments in how you would rule out it was not involved in primary tumor growth, but it is involved in growth at the secondary site. What could be the pitfalls of your experimental set-up? (limit 2 pages; 10 pts)

Please type answers, written answers are hard to read.

Answer 1

Before answering the given question, it would be imperative to understand the basic difference between cancer and metastasis. The word "cancer" literarily means uncontrolled or abnormal cell division. The word "metastasis" means migration or dislodging of cancerous cells from the primary site of development to the secondary site leading to tumorous growth. In general, cancer falls into two categories i.e. benign (harmless and localized) and malignant (harmful and often migratory). The term metastasis often refers to a malignant tumor. Usually, in the metastatic form of cancer, abnormal cells migrate from the primary site through lymphatic and/or circulatory system (blood), invade tissues or organs at a different site. Also, during metastatic cancer, a process of angiogenesis plays a significant role where new blood vessels are formed that divert the flow of nutrition to cancerous cells instead of normal cells or tissues.

When we think of the molecular mechanism of metastatic cancer development, it is essential to note that it is a cascade of reactions involving multiple intermediates. It generally involves tissue invasion, intravasation (penetration of cancerous cells into lymphatic or vasculatory system), extravasation (invading extracellular matrix), attachment, and proliferation of cells to new locations forming secondary tumors.

A mutation in proto-oncogene could result in the activation of oncogenes leading to an uncontrolled rate of cell division. The inactivation of the tumor suppressor gene leads to the development of cancer. These genes are solely responsible for the growth and development of primary tumors. The genes responsible for metastasis always function downstream of oncogenes. When one believes that protein named "D" has a role in the metastatic process, it can't be an oncogene and so not responsible for primary tumor growth or development. As it functions downstream of oncogenes, it may be responsible for traveling of cancerous cells to a different location, penetration into tissues or extracellular matrix, etc. So, to test this hypothesis, we must study the function or role of protein D. The gene expression studies (e. g. DNA microarray) could be useful to identify the role of metastaic genes. It reveals the upregulation or downregulation of genes involved in cancer. The techniques such as subtractive hybridization, microcell-mediated chromosome transfer, or RNAseq can be helpful to identify suppressor genes that regulate metastatic process. Other potential methods involve the use of multiple types of RNAs, subtractive hybridization, etc. While setting up an experiment, one has to keep in mind that the role of a particular protein decides its site of action whether primary tumor or tumor at a secondary site. As multiple suppressor and promoter genes regulate the process of metastasis, it would be a difficult task.