Practice Questions

TLS Online TPP Program

#Question id: 1384

Mutations that block expression of the E-cadherin gene are thought to be an important step in metastasis. To better understand how loss of E-cadherin contributes to metastasis, scientists created two cell lines that differed in their expression of E-cadherin. One cell line expressed normal E-cadherin, but at 10% of the usual levels. The other cell line expressed normal E-cadherin at the usual levels, and also, at high levels a mutant form that included the cytoplasmic domain but lacked the rest of the protein. Both cell lines exhibited strongly reduced cell adhesion in culture. However, only the cell line with reduced expression of normal E-cadherin metastasized when introduced into mice.

Which of the following hypotheses is most consistent with the observations on cell adhesion and metastasis in these cell lines?

#Unit 4. Cell Communication and Cell Signaling

Loss of E-cadherin releases signalling proteins that normally bind to its cytoplasmic domain, but promote metastasis when free.
The cytoplasmic domain of E-cadherin binds proteins required for cell adhesion, but those proteins are not involved in metastasis.
The E-cadherin transmembrane domain by itself is sufficient to promote the cell–cell adhesion that prevents metastasis.
The loss of adhesion caused by inactivation of E-cadherin is sufficient to explain how E-cadherin mutations promote metastasis.