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hi. cancerous cell may exhibit different receptors in their membrane (exposed to extracellular media) than healthy cells. in some cancer, thoses receptors may allow the cell to "refuse" to kill themselves (and so clear the ill cell) by a natural mechanism.

consequently, antibodies (wherever they came, naturally produced by the body, or by RNA vaccines) that targets thoses receptors should be able to recognize a cancerous cell in a normal population and engage the immune system in the elimination of the cell.

This is correct, but I don't think it quite answers the OP's question.

I believe they're asking why, if those cancer-specific cell surface markers are already present on the surface of malignant cells in the body, the immune system doesn't generate antibodies to them.

In other words, what's special about an mRNA vaccine and the way it presents tumor-associated antigens to the body that prompts an immune response and antibody generation, when those same antigens don't do anything by themselves when they're sitting on the surface of a cancer cell?

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as the other commenter said, this doesn’t answer the question of why need the mRNA vaccine to activate that response from the immune system when those chemicals are already present in cancerous cells in the body

The immune system is very adapt in recognizing foreign biological matter like bacteria, viruses and even another eucaryote organism's cells.

On the other hand, the body selects it's own immune cells for low responsiveness to its own proteins to prevent autoimmunity.

Cancer is essentially constituted of a body's very own cells gone aberrant. That means, these cells usually share several of the following characteristics:

• Internally and/or externally unregulated growth, proliferation, and expansion
• Loss of tissue function
• Migration to neighbouring tissues
• Denial of internal and/or external apoptotic stimuli (self-destruction)
• Evasion of immune cell recognition
• Inhibition of immune cell signalling

To break it down in terms of your question: cancer cells are naturally less likely to be targeted by immune cells than external pathogens, as they are basically a body's own cells. Immune cells, nevertheless, will kill wildly aberrant cells rapidly. That basically means cancer cells are naturally selected for variants that circumvent this line of defense. Either, they lose receptors by which they are primarily recognized by immune-cells, or gain/upregulate mechanisms by which they suppress immune cell-responses despite proper recognition.

Now, mRNA vaccines can reverse these effects by different mechanisms. You could potentially use them to

• increase the expression of receptors the immune cells use naturally
• decrease the expression of receptors inhibiting immune cell response
• introduce new epitopes the body knows how to react to, like surface proteins of a bacterium

All of these increase efficiency, efficacy and precision of the immune cell response against the targeted tumor cell.

you're absolutely right and apologize for it. read too quickly!

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