Can you elaborate by what you mean by "the purity wasn't good".

Do you mean there was a lot of DNA also? - that's an easy fix with DNase treatment.

Or do you mean the RNA was degraded? That requires starting over with new samples.

Cut tumour into small pieces (~5×5x5 mm), immediately submerge completely in ~10× volume RNAlater (tissue:RNAlater ≈ 1:10), keep at 4°C overnight to allow penetration, then transfer to −80°C for long-term storage; process for RNA extraction from thawed tissue after removing excess RNAlater. After removing excess RNAlater, place the tissue into the RNA lysis buffer and then homogenize the tissue thoroughly using an appropriate homogenizer (e.g., bead mill or rotor-stator). RNA was then isolated following the manufacturer’s protocol for the respective kit or manually