Which of the following statements describes a characteristic of cancer?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Cancer cells can metastasise.
In the body, cell growth and division are tightly controlled. In cancer cells this control breaks down. Normal cells stop dividing when they touch other cells; this is contact inhibition. Cancer cells have lost it, so they keep dividing and form tumours. Cells from a malignant tumour can spread to new sites; this is metastasis.
Option (1) Viruses are responsible for all types of cancer. — Incorrect. Viruses (oncogenic viruses) are only one cause. Cancer can also be caused by physical agents such as X-rays and UV, and chemical agents such as those in tobacco smoke.
Option (2) All tumors are classified as cancers. — Incorrect. Benign tumours stay in their original place, do not spread and cause little damage. Only malignant tumours invade and spread.
Option (3) Cancerous cells exhibit contact inhibition. — Incorrect. It is normal cells that show contact inhibition. Cancer cells have lost contact inhibition, which is why they keep dividing.
Option (4) Cancer cells can metastasise. — Correct. Cells from malignant tumours reach distant sites through the blood and start new tumours there.
NCERT Extract:
Cancer – “… Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Cancer cells appears to have lost this property. As a result of this, cancerous cells just continue to divide giving rise to masses of cells called tumors. Tumors are of two types: benign and malignant. Benign tumors normally remain confined to their original location and do not spread to other parts of the body and cause little damage.”
Cancer – “… Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there. This property called metastasis is the most feared property of malignant tumors. Causes of cancer : Transformation of normal cells into cancerous neoplastic cells may be induced by physical, chemical or biological agents.”