Bone marrow autotransplantation for solid tumors--prospects

Autologous bone marrow transplantation (AuBMT) is in clinical trial for patients with metastatic solid tumors, particularly breast cancer. This review deals with the potential of this approach. AuBMT is curative for the leukemias and lymphomas. Curative cancer chemotherapy has, almost without exception, required combinations of agents wherein dose was well maintained. However, curative chemotherapy strategies for the hematologic neoplasms have not proven successful for the common solid tumors. An important exception is that standard adjuvant chemotherapy can "cure" some micrometastatic tumors. Preclinical studies indicate the effectiveness of alkylating agents in terms of maintained dose effect through multiple logs of tumor cell kill; difficulty in developing drug resistance; general lack of cross resistance; and synergy for alkylating agents used in combination. There is an increasingly effective experimental basis for the construct of intensification regimens employing combinations of alkylating agents. Differing nonmyelosuppressive toxicity for alkylating agents provides a basis for maintaining dose when employed in combination in the autologous marrow situation. The aforementioned studies and cytokinetic analyses of combined intensive alkylating agent therapy for breast cancer support the potential of this approach. Clinical trials indicate a high response rate in refractory breast cancer. Trials involving induction chemotherapy followed by combined alkylating agent intensification have produced substantial complete remission rates. The duration of response has, in most studies, been short. This approach is associated with major toxicity, including mortality, and is expensive. Experimental and preliminary clinical evidence as marshalled in this review indicate that this is a promising area for therapeutic research.     

Characterization of two different cytoplasmic protein tyrosine kinases from human breast cancer

Two different protein tyrosine kinases were detected in the cytosolic fraction of different human tumor tissues. After partial purification, the two enzymes, which were highly active in breast tumor tissues, were characterized. One of them, soluble tyrosine kinase-1 (STK-1), represents a soluble form of the c-Src protein, which is apparently underphosphorylated on its C-terminal tyrosine residue whereas the other (STK-2) is a 48-kDa protein tyrosine kinase (PTK), which is molecularly and functionally related to the C-terminal Src kinase (Csk). These two protein tyrosine kinases clearly exhibit a different substrate specificity, and are responsible for the high tyrosine kinase activity present in the cytosolic fraction of human breast cancer. In addition, it was observed that STK-1 and STK-2 are also expressed in the breast cancer cell line, CAL-51.      

Familial hypomagnesemia maps to chromosome 9q, not to the X chromosome: genetic linkage mapping and analysis of a balanced translocation breakpoint

Familial hypomagnesemia with secondary hypocalcemia (HSH) (MIM 307600) was studied in three inbred Bedouin kindreds from Israel. The three kindreds, one extended and two nuclear families, contained 13 affected individuals, 11 males and two females. Assuming that the individuals affected with hypomagnesemia shared a chromosomal region inherited from a common ancestor, we used a DNA pooling strategy in a genome-wide search for loci which show homozygosity for shared alleles in affected individuals. DNA samples from affected individuals within a single kindred were pooled and used as the template for PCR amplification of short tandem repeat polymorphic markers (STRPs). Pooled DNA from unaffected siblings and parents were used as controls. A shift towards homozygosity was observed in the affected DNA pool compared with the control pools with D9S301 (GATA7D12). Genotyping of individual DNA samples with D9S301 and several flanking markers confirmed linkage to chromosome 9 with maximum LOD scores of 3.4 (theta = 0.05), 3.7 (theta = 0) and 2.3 (theta = 0) for the three families. We have identified a 14 cM interval on chromosome 9 (9q12-9q22.2), flanked by proximal marker D9S1874 and distal marker D9S1807, within which all affected individuals from the three kindreds are homozygous for a shared haplotype. The disease segregates with a common affected haplotype in the three families, suggesting that hypomagnesemia is caused by a common ancestral mutation in these families. Although HSH has been previously reported to be X linked, these linkage data demonstrate that the disorder is an autosomal recessive disease in these kindreds. Mapping of a chromosomal breakpoint in a somatic cell line established from a patient with HSH and a balanced X;9 translocation placed the chromosomal breakpoint in a 500 kb region flanked by D9S1844 and D9S273. Identification of the gene responsible for hypomagnesemia will provide insight into the regulation of this essential cation.      

Effect of recombinant human granulocyte-macrophage colony-stimulating factor on chemotherapy-induced myelosuppression

An increase in the dose of chemotherapy enhances the response of many experimental and clinical cancers, but the extent of dose escalation is often limited by myelosuppression. In preliminary trials, recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) has augmented leukocyte numbers and function, but the optimal dose is not established. We treated 16 adults who had inoperable or metastatic sarcomas with escalating doses of rhGM-CSF before and immediately after a first cycle of chemotherapy (cycle 1) to assess hematologic response and toxicity. A second cycle of chemotherapy (cycle 2) was given without rhGM-CSF. RhGM-CSF was tolerated well at doses of 4 to 32 micrograms per kilogram of body weight per day. At 64 micrograms per kilogram per day, edema and thrombi around a central venous catheter developed in two of four patients. Leukocyte and granulocyte counts increased significantly during the rhGM-CSF infusion. Neutropenia after cycle 1 was significantly less severe and shorter in duration than after cycle 2 (P less than 0.01). Mean total leukocyte and platelet nadirs were 1.0 and 101 x 10(9) per liter for cycle 1 and 0.45 and 44 x 10(9) per liter for cycle 2 (P less than 0.01), and the median intervals from day 1 of chemotherapy to neutrophil recovery (greater than 0.500 x 10(9) per liter) were 15 and 19 days, respectively (P less than 0.01). The duration of neutropenia was 3.5 days with cycle 1 and 7.4 days with cycle 2 (P less than 0.01). We conclude that rhGM-CSF is tolerated well at doses up to 32 micrograms per kilogram per day and is biologically active in leukopenic patients. It merits further evaluation for the prevention of morbidity from chemotherapy.     

A Phase I Study of High-dose BCNU,Etoposide and Escalating-dose Thiotepa (BTE) with Hematopoietic Progenitor Cell Support in Adults with Recurrent and High-risk Brain Tumors

This phase I dose-escalation study was performed to determine the tolerability of three-drug combination high-dose BCNU (B) (450 mg/m²), escalating-dose thiotepa (500–800 mg/m²) and etoposide (1200 mg/m²) in divided doses over four days in 22 adults with malignant primary brain tumors. Patients received G-CSF and hematopoeitic support with peripheral blood progenitor cells (PBPC) (n=18) or both PBPC and marrow (n=4). The maximum tolerated dose of thiotepa with acceptable toxicity was determined as 800 mg/m². The 100-day mortality rate was 9% (2/22). Grade III/IV toxicities included mucositis (71%), diarrhea (29%), nausea/vomiting (19%), and hepatic toxicity (14%). Neurological toxicities occurred in 24% and included seizures (two patients) and encephalopathy (three patients). Encephalopathy was transient in two patients and progressive in one patient. All patients had neutropenic fever. Median time to engraftment with absolute neutrophil count (ANC) >0.5×10⁹/l was 10 days (range 8–30 days). Platelet engraftment >20×10⁹/l occurred after 11 days (range 9–65 days). In the eighteen patients supported solely with PBPC, there was a significant inverse correlation between CD34⁺ dose and days to ANC (rho=–0.78, p=0.001) and platelet engraftment (rho=–0.76, p=0.002). Overall, 11% of evaluable patients (2/18) had a complete response to BTE. Median time to tumor progression (TTP) was 9 months, with an overall median survival of 17 months. BCNU (450 mg/m²), thiotepa (800 mg/m²) and etoposide (1200 mg/m²) in divided doses over four days is a tolerable combination HDC regimen, the efficacy of which warrants further investigation in adults with optimally resected chemoresponsive brain tumors.