A 54-year-old Woman Had An Episode Of Coughing With Blood-streaked Sputum. On Physical Examination She Appeared Cachectic. A Chest X-ray Showed An Irregular Mass Lesion In The Right Lung. A Transbronchial Biopsy Was Done And On Microscopic Examination Showed Small Cell Anaplastic Carcinoma. She Was Treated With A Multidrug Chemotherapy Regimen And Had A Partial Response. However, Metastatic Disease Is Now Present Eight Months Later. A Second Chemotherapy Protocol Is Tried, But No Response Is Noted.

Which Of The Following Is The Most Likely Reason For Failure Of The Second Protocol To Elicit A Response?

A The Neoplastic Cells Have An Abnormal P53 Protein

B This Carcinoma Was Caused By A Viral Infection

C A Ras Oncogene Has Been Activated

D The Neoplastic Cells Have Increased P-glycoprotein

E There Is A Second Primary Lung Cancer Present

answer / Explanation:

(d) Correct.

The Increase In P-glycoprotein Allows The Cells To Pump Out Any Toxin, Including Any Chemotherapy Agent.