Neoplasia Practice Questions

Q: The degradation of p53 through Ubiquitin-dependent proteolysis is facilitated by the binding of high-risk HPV protein.

E6. **Explanation:** The pathogenesis of Human Papillomavirus (HPV) in cervical cancer is primarily driven by two high-risk viral oncoproteins: **E6 and E7**. These proteins disrupt the cell cycle by targeting tumor suppressor proteins. **1. Why E6 is the correct answer:** The **E6 protein** of high-risk HPV types (16 and 18) binds to a cellular protein called **E6-Associated Protein (E6-AP)**, which acts as a ubiquitin ligase. This complex then binds to the **p53 tumor suppressor protein**, leading to its polyubiquitination and subsequent degradation via the **26S proteasome**. Since p53 is responsible for G1 arrest and apoptosis in response to DNA damage, its loss leads to uncontrolled cell proliferation and genomic instability. **2. Why other options are incorrect:** * **E7:** This protein primarily targets the **Retinoblastoma (Rb) protein**. E7 binds to Rb and displaces the E2F transcription factor, pushing the cell into the S-phase. It does not directly cause the ubiquitin-mediated degradation of p53. * **E8:** This is a minor protein involved in regulating viral DNA replication and maintaining latency; it does not play a direct role in p53 degradation. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **E6** targets **p53** (6 is close to 5); **E7** targets **Rb** (7 is close to 8/Rb). * **High-risk HPV types:** 16, 18 (most common), 31, and 33. * **Low-risk HPV types:** 6 and 11 (cause Genital Warts/Condyloma Acuminata). * **Koilocytes:** Pathognomonic finding on Pap smear (cells with perinuclear halo and wrinkled "raisinoid" nuclei). * **Vaccine:** Gardasil-9 covers types 6, 11, 16, 18, 31, 33, 45, 52, and 58.

Q: Which of the following is not a cyclin-dependent kinase (CDK) inhibitor?

p53. **Explanation:** The cell cycle is strictly regulated by **Cyclin-Dependent Kinases (CDKs)** and their inhibitors (CKIs). CKIs are categorized into two families: the **Cip/Kip family** (p21, p27, p57) and the **INK4 family** (p15, p16, p18, p19). **Why p53 is the Correct Answer:** **p53** is a **tumor suppressor protein**, often called the "Guardian of the Genome." It is not a direct CDK inhibitor itself [1]. Instead, it acts as a transcription factor. When DNA damage occurs, p53 levels rise and trigger the transcription of **p21**, which then binds to and inhibits CDK complexes to arrest the cell cycle [1]. Thus, while p53 *regulates* inhibitors, it does not belong to the biochemical class of CDK inhibitors. **Analysis of Incorrect Options:** * **p21 (Cip1):** A potent CDK inhibitor induced by p53. it inhibits a wide range of CDK-cyclin complexes (especially CDK2), leading to cell cycle arrest in the G1 phase. * **p27 (Kip1):** Responds to growth inhibitory signals (like TGF-β). It binds to and inhibits Cyclin E-CDK2 and Cyclin D-CDK4 complexes. * **p57 (Kip2):** A member of the Cip/Kip family primarily involved in embryogenesis. Mutations in the p57 gene are associated with **Beckwith-Wiedemann syndrome**. **High-Yield NEET-PG Pearls:** * **INK4 Family:** Specifically inhibits **CDK4 and CDK6** (involved in G1 progression). * **p16:** A member of the INK4 family; its expression is a marker for HPV-related cervical and oropharyngeal cancers. * **Rb Protein:** The "molecular brake" of the cell cycle; when phosphorylated by CDKs, it releases E2F to allow S-phase entry [1]. p53 and Rb are the two most commonly mutated genes in human cancers.

Question 1

Which benign tumor is known to show metastasis?

Accepted Answer

Ameloblastoma

Answer

Warthin's tumor

Answer

Keratocanthoma

Answer

Neurofibroma

Question 2

Which of the following tumors is most likely associated with either hyponatremia or diffuse pigmentation of the skin?

Accepted Answer

Small cell carcinoma of the lung

Answer

Renal adenocarcinoma

Answer

Hepatocellular carcinoma

Answer

Primary squamous cell carcinoma of the lung

Question 3

Which of the following childhood tumors most frequently metastasizes to the bone?

Accepted Answer

Neuroblastoma

Answer

Ganglioneuroma

Answer

Wilms' tumor

Answer

Ewing's sarcoma

Question 4

Thorium dioxide is known to cause which of the following malignancies?

Accepted Answer

Angiosarcoma

Answer

Lymphoma

Answer

Lymphangiosarcoma

Answer

Hemangioendothelioma

Question 5

The degradation of p53 through Ubiquitin-dependent proteolysis is facilitated by the binding of high-risk HPV protein.

Accepted Answer

E6

Answer

E6 and E7

Answer

E7

Answer

E6, E7 and E8

Question 6

Which of the following markers is not typically expressed by neuroendocrine tumors?

Accepted Answer

CK7

Answer

Synaptophysin

Answer

Chromogranin

Answer

CD56

Question 7

Which of the following tumors is associated with BRAF mutation?

Accepted Answer

Adenocarcinoma of the colon

Answer

Medullary thyroid carcinoma

Answer

Hodgkin's lymphoma

Answer

Hepatocellular carcinoma

Question 8

A 58-year-old woman with colon cancer presents with 3 months of increasing shortness of breath. A chest X-ray reveals numerous, bilateral, round masses in both lungs. Histologic examination of an open-lung biopsy discloses malignant gland-like structures, which are nearly identical to the colon primary. Which of the following changes in cell behavior was the first step in the process leading to tumor metastasis from the colon to the lung in this patient?

Accepted Answer

Invasion of the underlying basement membrane

Answer

Arrest within the circulating blood or lymph

Answer

Exit from the circulation into a new tissue

Answer

Penetration of vascular or lymphatic channels

Question 9

Defective DNA repair is seen in all of the following conditions EXCEPT?

Accepted Answer

Friedreich's ataxia

Answer

Xeroderma pigmentosum

Answer

Werner syndrome

Answer

Bloom syndrome

Question 10

Which of the following is not a cyclin-dependent kinase (CDK) inhibitor?

Accepted Answer

p53

Answer

p21

Answer

p27

Answer

p57

Neoplasia — MCQs

Neoplasia — MCQs

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