I asked AI (not chatgpt), this is what it said:

What Nattokinase Actually Is:

• Enzyme from fermented soybeans (natto)
• Has fibrinolytic activity - breaks down fibrin (blood clot protein)
• Used for cardiovascular health, some evidence for blood thinning

The "Fibrin Sheath" Concept
Cancer cells do sometimes get coated in fibrin - this is part of how they can evade immune detection and stick in new locations during metastasis. However:

• It's not a protective "sheath" that contains the cancer
• It's more like a camouflage/cloaking mechanism
• Breaking it doesn't "expose" cancer to immune system in a helpful way
• Fibrin also helps tumors grow blood vessels (angiogenesis)

Your Specific Questions
Does nattokinase destroy fibrin around tumors?

• In theory, possibly some effect on fibrin
• No clinical evidence it penetrates tumor microenvironment at useful concentrations
• No human trials showing anti-cancer efficacy

Would this cause metastasis like a biopsy?

• Biopsy-caused metastasis is rare and controversial itself
• Nattokinase wouldn't mechanically spread cells like a needle
• But fibrin disruption could theoretically affect tumor behavior unpredictably

Does it expose cancer to immune system?

• Oversimplified. The immune system often already sees cancer but fails to respond effectively
• Fibrin removal alone doesn't guarantee immune activation
• Cancer immune evasion is far more complex than just fibrin coating

The Bottom Line
No clinical evidence supports nattokinase as cancer treatment. The mechanistic reasoning sounds plausible but:

• Doesn't account for cancer biology complexity
• Ignores that disrupting tumor microenvironment can have pro- and anti-tumor effects
• No human data showing benefit