Why can a HeLa cell survive with such an abnormal karyotype?

Why do you think a cell line such as HeLa could survive with a grossly abnormal karyotype whereas an embryo can not?
I understand that HeLa cells are cancerous but I am not sure how to approach this question.
Any help is appreciated =)
Update: I know that cancer cells are immortal lol I'm just wondering how the karyotype comes into effect.
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