Control of a human tumour (Ewing sarcoma) in mice by a single lethal dose of dimethyl-myleran and bone marrow

High-dose chemoradiotherapy (HDC) in the Ewing family of tumors (EFT)

EFT is defined by the expression of ews/ets fusion genes. The type of the fusion transcript impacts on the clinical biology. EFT requires risk adapted treatment. A risk-adapted treatment is determined by tumor localisation, tumor stage and volume. For metastatic and relapsed disease the pattern of spread and the time of relapse are the determinants of risk stratification. Staging of Ewing tumors has been considerably improved by magnetic resonance imaging and modern isotope scanning techniques. However, the determination of the extent of the metastatic spread in particular number of involved bones remains an unresolved issue. The prognosis for high-risk Ewing tumors has been improved by multimodal and high-dose radio/chemotherapy (HDC). The concepts for high-dose therapy in Ewing tumors are based on dose response and dose intensity relationships. In single agent HDC most experience exists with Melphalan. Several chemotherapeutic agents have been used in combination HDC with or without TBI such as Adriamycin, BCNU, Busulphan, Carboplatin, Cyclophosphamide, Etoposide, Melphalan, Thiotepa Procarbazin and Vincristine. To date, superiority of any high-dose chemotherapy regimen has not been established. However, the clinical biology, the pattern of spread and the time of relapse determine the prognosis of patient who are eligible for HDC. In particular, patients with multifocal bone or bone marrow metastases have a poorer prognosis than patients with lung metastases. In addition, patients with a relapse within 24 months have a poorer prognosis than patients with a relapse later than 24 months after diagnosis. This review will analyze the results of single- and multi-agent chemotherapy with respect to agent combination, dose and risk stratum of patient population. Future therapeutic modalities for the treatment of EFT might encompass immunotherapeutic and genetic strategies including allogeneic stem cell transplantation.

Xenografts in pharmacologically immunosuppressed mice as a model to test the chemotherapeutic sensitivity of human tumors

A human tumor xenograft model using pharmacologically immunosuppressed mice was assessed for its suitability to test preclinically the sensitivity of colorectal carcinomas, bone sarcomas and melanomas against anticancer agents. Besides ionizing radiation, 14 cytotoxic drugs including 5-fluorouracil (5-FU), dimethylmyleran (DMM), cytosine arabinoside, cyclophosphamide, melphalan, BCNU, mitomycin C, adriamycin, bleomycin, etoposide, vinblastine, cisplatin, procarbazine and DTIC were assayed. Ionizing radiation, 5-FU and DMM were also applied at lethal doses followed by bone-marrow rescue heavy therapy. Four colon carcinomas responded poorly to most of the agents but one tumor displayed marked sensitivity to BCNU. Lethal doses of radiation, 5-FU and DMM could also show considerable activity. High sensitivity was shown by a Ewing sarcoma to DMM and cyclophosphamide and by an osteosarcoma to the latter drug. No strong effects were seen against melanomas. Lethal doses of DMM induced the best regression of one colon carcinoma. In general, the superiority of heavy therapy for solid human tumors compared to maximally tolerated doses was demonstrated. Individual carcinomas of the same type displayed different drug sensitivity.

Protection by bone marrow grafts against lethal doses of 5-fluorouracil

C3H (H-2k) mice were treated with lethal doses of the antimetabolite 5-fluorouracil (5-FU). After 16 hr the mice received an intravenous injection of 25 X 10(6) syngeneic or allogeneic bone marrow cells. With syngeneic cells, survival after a single dose of 350 mg/kg 5-FU was increased from 27 to 83% and after 450 mg/kg 5-FU from 14 to 84%. Allogeneic CBA (H-2k) donor cells allowed 81% of the mice to survive after 350 mg/kg 5-FU and 42% after 450 mg/kg 5-FU. Allogeneic marrow from A (H-2a) donors was ineffective after both doses of 5-FU. The results show that the lethality of 5-FU is largely prevented by a hemopoietic graft. Experimentally, 5-FU belongs to the agents which may be applied in cancer chemotherapy at lethal and thus potentially tumor-eradicative doses in combination with autologous or syngeneic bone marrow. In humans it remains to be seen whether the use of this protocol is precluded by prevailing gut toxicity.

Decreased tolerance to dimethyl-myleran, cyclophosphamide and radiation in lymphoma-bearing mice

A lethal dose of the cytotoxic agent dimethyl-myleran (DMM) is survived by 75-100% of mice reinfused with autologous bone marrow. In mice inoculated beforehand with a syngeneic Moloney lymphoma and then treated with lethal DMM, hemopoietic restoration and survival are compromised. With subcutaneous tumour challenge, in the face of substantial early toxicity, a therapeutic effect of DMM prevails. With intravenous or intraperitoneal tumour challenge the restorative potency of the autograft and thus the therapeutic drug effect are lost since practically all animals die from DMM. The reduced tolerance of mice carrying the Moloney lymphoma applies more generally to cytotoxic measures. The toxicity from sublethal doses of DMM, cyclophosphamide (CY) and total-body irradiation (TBI) is increased in mice inoculated subcutaneously shortly before with the lymphoma cells. The LD50 of the three agents is reduced by up to 70% according to the number of injected tumour cells or the time allowed for their multiplication. The effect is also provided by a cell-free tumour filtrate. Since the filtrate reduces bone marrow cellularity, the decreased tolerance could be due to the impairment of hemopoiesis by a tumour factor. Two human cancers growing as xenografts in immunosuppressed mice did not increase the sensitivity to DMM.

Comparative growth of human tumors in pharmacologically immunosuppressed, immune-deprived, cyclosporin A-treated and nude mice

The growth of three human tumor xenografts, namely an Ewing sarcoma, a colon carcinoma and an osteosarcoma, was compared in nude and conditioned mice. Conditioning protocols included (1) immune deprivation (thymectomy, lethal irradiation and cytosine arabinoside pretreatment); (2) immunosuppression with procarbazine, cyclophosphamide and antithymocyte serum; and (3) continuous administration of cyclosporin A. Similar tumor growth was seen in nude mice, immune-deprived mice and mice treated with the medium and high-dose immunosuppressive protocol. Cyclosporin A allowed only very modest tumor growth. In the main comparative experiment with the Ewing sarcoma and the colon carcinoma, overall survival was lowest with nude mice (17%), higher with immune-deprived mice (61%) and best with immunosuppressed mice (81 and 87%). For the screening of anticancer agents the immunosuppressive protocol consisting of synergistic procarbazine, cyclophosphamide and antithymocyte serum may be added to the already available models. It allows adequate tumor growth with good animal survival and does not require operative procedures and irradiation.