A research scientist injects hepatocellular carcinoma cells into the liver parenchyma of an experimental guinea pig. Serial observations show that the tumor cells progressively proliferate and invade the liver parenchyma to form a large mass. After some time, malignant cells begin to penetrate the vascular basement membrane to gain access to the circulation. During the process of basement membrane invasion, expression of which of the following substances is most likely to be increased in the tumor cells?

Question

A research scientist injects hepatocellular carcinoma cells into the liver parenchyma of an experimental guinea pig.  Serial observations show that the tumor cells progressively proliferate and invade the liver parenchyma to form a large mass.  After some time, malignant cells begin to penetrate the vascular basement membrane to gain access to the circulation.  During the process of basement membrane invasion, expression of which of the following substances is most likely to be increased in the tumor cells?

Quizplus · Accepted Answer

Metalloproteinases are zinc-containing enzymes that degrade components of the extracellular matrix (ECM) and basement membrane, which are composed primarily of laminin and collagens IV and VII. These enzymes participate in many physiologic processes, such as tissue remodeling and embryogenesis. They also facilitate basement membrane penetration, which distinguishes an invasive tumor from carcinoma in situ and includes the following steps: (Choice A) Acid hydrolases, which function at acidic pH, are primarily degradative lysosomal enzymes. (Choice B) In humans, alkaline phosphatase is concentrated in liver cells; elevated levels suggest an obstructive biliary process. (Choice C) Carboxypeptidases cleave peptide bonds at the carboxy-terminal; some participate in the synthesis of insulin and neuropeptides. (Choice E) Hyaluronic acid is an ECM component. Educational objective: Metalloproteinases are zinc-containing enzymes that degrade the extracellular matrix. They participate in normal tissue remodeling and in tumor invasion through the basement membrane and connective tissue.

A Research Scientist Injects Hepatocellular Carcinoma Cells into the Liver