Myeloma cells fused with spleen cells in hybridoma technology are:
The principle of cellular compartmentalization and cell cycle explains that SNARE-mediated trafficking, Hayflick limit, P53 and cyclin regulation control proliferation. Hence Hypoxanthine guanine phosphoribosyl transferase lacking cells fits best because it aligns with membrane trafficking and cell cycle control, as documented in authoritative sources on cell biology.
Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 17, Cell Cycle and Regulation, explains Cdc2, cyclins, P53, proteasomes, Hayflick limit, primary culture and immortalization mechanisms governing proliferation and genomic stability.