21. Cancer is often believed to arise from stem cells rather than fully differentiated cells. Following are certain views related to the above statement. Which one of the following is NOT correct?
    (1) Stem cells do not divide and therefore require fewer changes to become a cancer cell.
    (2) Cancer stem cells can self-renew as well as generate the non-stem cell populations of the
    tumor.
    (3) Terato-carcinomas prove tumors arise from stem cells without further mutations.
    (4) Stemness genes can often function as oncogenes.

The statement which is NOT correct regarding the view that cancer arises from stem cells rather than fully differentiated cells is:

(1) Stem cells do not divide and therefore require fewer changes to become a cancer cell.

Explanation:

• Stem cells are characterized by their ability to divide and self-renew throughout life. They have a long lifespan and high proliferative capacity. These properties actually make them more likely candidates for accumulating mutations leading to cancer. So, the statement saying stem cells “do not divide” is incorrect.

• Cancer stem cells (CSCs) can indeed self-renew and generate diverse populations within tumors, contributing to heterogeneity and tumor maintenance.

• Teratocarcinomas are tumors derived from pluripotent stem cells and support the notion that tumors can arise from stem cells, but additional mutations usually occur to produce malignancy, not “without further mutations” as in option (3), which is generally an oversimplification.

• Many stemness genes (genes regulating properties of stem cells) are often found to function as oncogenes, playing roles in tumor initiation and progression.

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