Can a regular speaker cables PVC jacket survive 120°C atmosphere? Or do I have to use some other cable?
You have to use some other cable.
I usually go with Teflon in difficult thermal situations.
In general, the thermal performance of PVC may be severely inadequate for the 120°C conditions you've mentioned. Many forms of PVC insulation are rated as low as 80°C. Here are some supporting references to back up this claim:
Semi-Rigid PVC (SR-PVC) under the
UL Style 1007, CSA TR-64 under
Polyvinylchloride (PVC) Insulated UL/CSA Hook-Up Wire:
PolyVinyl Chloride (PVC) under the