This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Substance playing a role in tumor metastasis cascade is \nSelect and explain. \nA. Collagenase IV, B. TNF-alpha, C. CD99, D. NM23', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans is 'a' i.e. Collagenase IVVarious steps of metastasis and molecules involvedDetachment of tumor cells - Down regulation of expression of either E-cadherins or cateninsAttachement to ECM (including basement membrane) - Tumor cells express integrins that helps in the attachement.Degradation of ECM - proteolytic enzymes (most impoant proteases are metalloproteinases (MMPs) including collegenase IV).Vascular dissemination and homing of tumor cells - Among adhesion molecule CD44 is of paicular interest.", 'role': 'assistant'}]