Correct option is C
Explanation-
Statement A: Increased telomerase expression always contributes to increased cell death in cancer cells.
Telomerase is an enzyme that adds repetitive DNA sequences to the ends of chromosomes (telomeres). In most normal somatic cells, telomerase is inactive, so with each division, telomeres shorten. Eventually, this triggers senescence (growth arrest) or apoptosis. In cancer cells, telomerase is re-activated, allowing cells to divide indefinitely. Telomerase prevents cell death by maintaining telomere length.
This immortalizes cancer cells, allowing continuous proliferation.
So, this statement is incorrect.
Statement B: Overproduction of anti-apoptotic protein (Bcl2) can lead to inappropriate cell survival and is associated with chronic lymphoblastic leukemia (CLL).
Bcl2 (B-cell lymphoma 2) is a key anti-apoptotic protein. It acts by inhibiting mitochondrial pathways of apoptosis, allowing cells to survive under conditions where they should die. In CLL (chronic lymphocytic leukemia), Bcl2 is often overexpressed due to chromosomal translocations. This overexpression prevents apoptosis, allowing abnormal lymphocytes to accumulate. Bcl2 blocks programmed cell death, contributing to the persistence of malignant cells. So, this statement is correct.
Statement C: The E5, E6 and E7 proteins encoded by human papilloma virus (HPV) are tumor suppressors.
HPV is associated with cervical and other cancers. It expresses oncogenic (cancer-causing) proteins. These proteins are not tumor suppressors, they are oncoproteins. They contribute to tumor formation by disabling host tumor suppressors. E6 and E7 inactivate p53 and Rb, promoting uncontrolled cell division. So, this statement is incorrect.
Statement D: Overexpression of cyclin D1 or loss of p16 and Rb can cause inappropriate, unregulated passage through the restriction point in late G1.
The G1 checkpoint (also called the restriction point) is a critical control in the cell cycle. It ensures cells only proceed to DNA replication (S phase) if conditions are right.
Cyclin D1: Drives cells through G1 by activating CDK4/6.
p16: A tumor suppressor that inhibits Cyclin D-CDK4/6.
Rb (Retinoblastoma protein): Binds and inhibits E2F, a transcription factor needed for S phase.
Overexpressed Cyclin D1 or loss of p16 or Rb removes these regulatory brakes. This allows cells to enter S phase unchecked, contributing to genomic instability and cancer.
So, this statement is correct.
Correct Option c — B and D
