Are tumor-associated antigens found only on the membrane of cancerous cells or just over-expressed on the membrane of carcinogenic cells?

In other words, are these antigens also found on healthy cells?

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  • $\begingroup$ Welcome to Biology.SE! We encourage you to do some research on your own and ask questions informed by what you have already learned. In particular, your question assumes that all cancer antigens are the same, which reading the brief wikipedia article on tumor antigens reveals to not be true. ——— Please also take the time to go through the tour and then the help pages starting with How to Ask questions effectively on this site. Thanks! 😊 $\endgroup$ – tyersome Aug 30 '19 at 20:12
  • $\begingroup$ @tyersome I already know that cancer antigens aren't all the same but I want to know if these antigens can be found also on healthy cells or at least in some rare cases? $\endgroup$ – ahmed ashraf Aug 31 '19 at 12:53

I'll answer a slightly different interpretation of the question, which is whether the proteins (epitopes, actually) that are presented by cancer cells are neoantigens (varieties of proteins that only occur in the cancer cell due to mutations) vs 'wild type' antigens that can be found in other non-cancerous cells, but are over-expressed (or improperly expressed) in the cancer cell.

For melanoma, some of the potentially most useful immune-system targets are 'normal' proteins that are over expressed in cancer cells and rarely expressed in non-cancer cells. These include cancer testis antigens, which are proteins normally mainly expressed in germ line cells, but are accidentally expressed on cancer cells and lead to these cells being targeted by t-cells. See (for instance) the paper Cancer testis antigen and immunotherapy, ImmunoTargets and therapy (2013), pp. 11-19. For non-small cell lung cancer, Analysis of GAGE, NY-ESO-1 and SP17 cancer/testis antigen expression in early stage non-small cell lung carcinoma.

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  • $\begingroup$ your answer is amazingly clear and useful $\endgroup$ – ahmed ashraf Sep 10 '19 at 14:11

Carcinogenic tumor associated antigens correspond to any peptide chain (antigen) which triggers an immune response from the host. This means that they can be found anywhere inside, at the membrane, and outside of the cell: inside the cell (intracellular), at the cellular membrane and exposed to the extracellular environment, or even secreted.

Depending on the oncogene, they can be also eventually be over-expressed (anywhere there are supposed to be, including the membrane of cells).

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  • $\begingroup$ It would be worth to mention that there is a major difference between antigens recognized by antibodies and peptide antigens presented by MHC-I, since especially in the tumor context small mutations make the latter ones more likely to be significantly different from endogenous non-immunogenic peptides/antigens $\endgroup$ – Nicolai Aug 30 '19 at 8:05
  • $\begingroup$ Good point Nicolai, thank you for your feedback, I'm going to edit my answer to include these points too. $\endgroup$ – Dr. H. Lecter Aug 30 '19 at 8:38
  • $\begingroup$ Your answer would also be improved by recognizing that antigens are not necessarily proteins/peptides — for example, they will often be carbohydrates. $\endgroup$ – tyersome Aug 30 '19 at 20:15

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