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I have seen haploid cancer cells (I think it was leukemia cells) in a lab.

Sperms and eggs are haploid but are not destroyed by the body because they are protected by other cells surrounding them.

My questions :

  • How are haploid and diploid cells differentiated by our immune system ?

  • Why are the haploid cancer cells not killed ? I know I could as well ask why any cancer cells are not killed but I want to know if there is anything specific about these cells ?

  • How are these cells generated ? (By meiosis ?!)

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Normally , tumor cells are destroyed by NK cells. Is this a case of autoimmunity ? –  biogirl Jan 6 at 13:13
    
No, autoimmunity causes the body to attack its own cells. The other thing: Haploid cancer cells don't really make sense, since they cannot divide due to the half set of chromosomes. I only did a short search in the Pubmed but besides artificially generated haploid stem cells and "near haploid" cancer cells, nothing pops up. Do you have any references? –  Chris Jan 6 at 13:28
    
@Chris I do not have references but I have seen the cells myself.I had gone for a camp at Stanford University and our instructor had shown them to us. I am sure they were haploid. –  biogirl Jan 6 at 14:16
    
@chris But aren't tumor cells our own cells too ? –  biogirl Jan 6 at 14:17
    
What makes you sure they were haploid? Yes, tumor cells are our own cells - but out of control. So it makes sense that the immune system removes them. In an autoimmune disease all cells of a certain type are attacked. –  Chris Jan 6 at 14:30

1 Answer 1

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Now that I did some research on this, it seems to be a very rare condition of acute lymphoblastic leukemia (ALL), see this article:"Chromosomes and causation of human cancer and leukemia. XLVII. severe hypodiploidy and chromosome conglomerations in ALL.". This article ("Origin of near-haploidy in malignant hematopoietic cells.") hypothesizes that this might happen through gradual chromosome loss during cancer formation and that in the end one clone with a lower than normal number of chromosomes.

This seems connected to a much worse outcome of the cancer than for hyperdiploidies (more chromosomes than normal). See the "Atlas of Genetics and Cytogenetics in Oncology and Haematology". They also define why haploid (or near haploid means: Less than thirty chromosomes, down to 23 have been observed). This is not the normal haploidy found in germ cells. Se also "Isolation and Characterization of a Near-Haploid Human Cell Line".

Since these chromosomal changes occur inside the nucleus I think this is mostly invisible to the immune system - so there is probably no difference how these cells escape the immune system compared to other cancer cells. I think its possible that due to the chromosomal loss some proteins which control apoptosis are lost, so the cells escape this fate as well. Regarding the immune question, you can either start with the following articles or simply go over to Pubmed and choose some articles. In this field there is a lot of research going on.

If there are access problems, let me know.

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