in this video we'll talk about the tumor antigens it's an antigenic substance which is produced by the tumor cells so why tumor antigens are useful tumor antigens are useful because they can be serving as a tumor biomarker so it it would Aid in diagnosis also there are tumor Associated antigens which are potential candidates for promising cancer therapy let us talk about tumor antigens in bit more details so this is a tumor cell which has grown in vicinity of normal cells now neoplastic cells are self cells they are just transformed into carcinogenic state and most of
the antigens that are present on the surface of tumor cells are actually self antigens so T Cell should not identify them as a foreign substance any immune response should not be worked however in cancer cells or in tumor cells there are specific set of antigens which are new or unique and these antigens might not be a present in a normal cell hence it can be detected by the immune system as foreign so potential immune response can be generated against them so that's the whole point of tumor Associated antigen or tumor antigens so imagine this is
a normal cell which is expressing a self peptide on MHC class 1 any cd8 positive T cells would not recognize this and they should not engage because long back due to Central tolerance and peripheral tolerance all self-reactive cd8 positive T cells were eliminated from the systems and this is a safeguard mechanism in our immune system but in cancer cells there are specific antigens which might be unique or there are some antigens which are existing antigens but mutated in that case those unique proteins would be detected by the cd8 positive T cytotoxic cells and that would
mount an immune response again these cell types and this is what happens in tumor so let us understand few more scenarios in bit more details so here in yellow you can see the normal cells and in pink you can see the cancer cells so in cancer cell you might have altered self-peptide which might have resulted due to a mutation that has generated a completely different or unique peptide and now that is presented on class 1 MHC so T cells can recognize that and engage in an alternate scenario you can imagine that there are specific oncopeptides
that are not present in normal cells and there is a inappropriate expression of these particular peptides in this cell type maybe these cells are only present in fetal State and not supposed to be present in the adult state but somehow these cells are now expressing this protein and that's why it is treated as a foreign in alternate scenario maybe there is a self protein but now it is over expressed or expressed in much more quantity than it is supposed to be and all this scenario might lead to an immune response or recognition of these cells
as a potential immune targets now let's talk about the classification of tumor antigens there are two broad categories tumor specific antigens and tumor Associated antigens as the name suggests tumor specific antigens are unique to tumor cells whereas tumor Associated antigens are normal cellular proteins with unique expression patterns so imagine there are there is a gene a whose product is protein a and there is a mutation in this particular Gena which is oncogenic mutation as a result of this mutation altered peptide is generated which is now displayed on the MHC class 1 molecule so this would
become a tumor specific antigen now imagine a situation where a particular cell expresses a particular protein which is present only in the fetus now this particular protein should not be expressed in an adult state but imagine in a cancer cell this protein is expressed that means that would this would be treated as a potential immune Target and this is known as tumor Associated antigens let us take some real life example to appreciate this better in markets lymphoma where ipsene bar Virus Infection has been reported the EBV proteins are displayed on class 1 MHC molecules or
on Class 2 MHC molecules and this particular evv proteins are treated as foreign antigens so immune cells engage against them in cervical cancer HPV E7 and E6 proteins are associated with cancer progression and immunity against these cancer cells now there are two well-studied onco fetal antigens which are Alpha phytoprotein and carcino embryonic antigen or cea among them Alpha phetoprotein is associated with ovarian cancer liver cancer testicular cancer and carcino embryonic protein or carcino embryonic antigen is associated with many other cancer types but in general they are found in liver cells when the fetus is two
to six months old and it's not supposed to be present in adults but now it is upregulated and found in colorectal cancer 90 of advanced colorectal cancer and 50 percent of the early stage colorectal cancer shows a cea elevation in the patient serum so it can also work like a biomarker for detection or staging of these cancer and now we understand what is the importance of tumor specific antigen or tumor Associated antigens I hope this was informative you can follow our Facebook page or Instagram page for more notes and flashcards you can support our Channel
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