Human pancreatic leiomyosarcoma (PZX-7) growing as a serially transplantable xenograft in immunosuppressed mice

Background. Several human leiomyosarcoma xenografts have been established, but pancreatic smooth muscle sarcomas have never been serially transplanted and investigated. Method. Immunosuppression of CBA/CA mice was achieved by thymectomy, whole- body irradiation, and bone marrow reconstruction. Tumor fragments were subc utaneously implanted from a Grade III pancreatic leiomyosarcoma and seriall y passaged for more than 24 mo. The xenografted tumors were characterized b y morphological, morphometrical, biochemical, and flow cytometric methods. Results. The tumor has retained its characteristic morphology and no furthe r differentiation occurred. The mitotic counts and the amount of the connec tive tissue all remained constant. The calculated volume doubling time was 11.3 d. Immunohistochemically, the tumor proved to be p53-negative, but the strong expression of the bcl-2 remained as a constant feature throughout s uccessive transplantations. The DNA index and the proliferation indices did not change significantly with the time (mean DI: 1.65, range: 1.561-1.70; mean PI: 17.9%, range: 15.3-20.7%). Lactose dehydrogenase (LDH) isoenzyme e lectrophoresis evidenced a retained human pattern of the tumor even after 3 2 mo of transplantations. Conclusion. The first human pancreatic leiomyosarcoma xenograft (PZX-7) gro wing in immunosuppressed mice is described and characterized.