To establish whether Obatoclax-induced lysosomal alterations are also observed in vivo, we treated thyroid cancer-carrying [Pten,Trp53]thyr−/− mice with vehicle or Obatoclax for 6 days, after which thyroid single cell suspensions were loaded with Lysotracker and analyzed by flow cytometry. The gene discussed is PTEN; the disease is thyroid gland carcinoma.