14. Animal cell cultures are frequently used for production of therapeutic proteins. NIH3T3 (a fibroblast cell line) and CHO (Chinese hamster ovarian cell line) are some of the popular cell lines used. Choose the best combination of cell line (for transfection) and starting material for purification of human growth hormone, a secretary protein
(1) NIH3T3 cell pellet
(2) CHO and cell pellet
(3) NIH3T3 and culture medium
(4) CHO and culture medium

The best choice is (4) CHO and culture medium.

Reasoning

Human growth hormone (hGH):

• Is a secretory protein synthesized in the ER and secreted out of mammalian cells.

• When expressed in mammalian lines like CHO, it is released into the culture medium, allowing easy harvest and proper folding/post‑translational modification.

Therefore, the best combination is:

• Cell line for transfection: CHO – robust, well‑characterized mammalian production host, widely used for biopharmaceuticals.

• Starting material for purification: culture medium, where secreted hGH accumulates.

Option-wise explanation

1. NIH3T3 cell pellet

   • NIH3T3 can be transfected, but hGH being secreted will be found mainly in the medium, not in the pellet.

   • Pellets require cell lysis and give low yields of secreted proteins.

2. CHO and cell pellet

   • Correct host but wrong starting material; secreted hGH is primarily in the supernatant, so using the pellet is inefficient.

3. NIH3T3 and culture medium

   • Medium is the right fraction, but NIH3T3 is not a common industrial production host for therapeutic proteins compared with CHO.

4. CHO and culture medium – correct

   • Combines the standard biopharmaceutical host (CHO) with the correct fraction (culture medium) for a secreted therapeutic protein like hGH.