Amplification of N-myc oncogene in human melanoma cells.

Tissue specimens from two melanoma patients and two patients with laryngeal carcinoma were studied for the expression of c-myc, N-myc and v-src oncogenes. Out of three different probes, only the N-myc probe one signalled amplification. While the two patients with laryngeal carcinoma showed only single copy of the N-myc gene in tumor cells, amplification of this gene was found in both two melanoma patients. The patients with 1 extra copy of the N-myc gene and its protein product had an early recurrence but is still alive, while the other melanoma patient with 4 extra copies of the gene, relapsed very early and died of melanoma within 7 months after diagnosis. Thus a higher amplification (4 extra copies) seems to correlate with very poor outcome of the disease.

Cytogenetic study of 130 patients with acute nonlymphocytic leukemia.

Results of cytogenetic examination of 130 patients (62 males and 68 females, mean age 48.7 +/- 18.7 years) with acute nonlymphocytic leukemia (ANLL) are presented. All patients were examined at the onset of the disease. According to the FAB classification, 35 (26.9%) patients were diagnosed as having M 1, 42 (32.3%) M 2,9 (6.9%) M 3, 29 (22.3%) M 4, 8 (6.2%) M 5 and 7 (5.4%) M 6 subtype of ANLL. Normal karyotype (NN) was found in 29 (22.3%) patients studied, normal and abnormal clones (AN) in 24 (18.5%) and abnormal chromosomes only (AA) in 77 (59.2%) patients. Thus 78% of patients showed a clonal karyotypic abnormality. Specific chromosomal abnormalities t(8;21), t(15;17), t(9;22), inv(16), del(16), del(11q) were found in 30.7% of AA and AN patients. Nonrandom chromosomal changes (+8, 5q--, --5, --7) were noted in 53.4% of them. Single chromosomal change was found in 40.5% of patients and complex changes with more chromosomal clones were presented in the test. Relationship between prognosis and chromosomal finding was evaluated.

The importance of blast cell DNA content for prognosis of childhood acute lymphoblastic leukemia.

The prognostic value of cellular DNA content measured by static cytophotometry was evaluated in 69 children with acute lymphoblastic leukemia (ALL) using the pretreatment distribution of the DNA content in blast cells of bone marrow and peripheral blood. The median follow-up of the whole group of patients was 45 months. Aneuploidy was detected in 71% of children, most of them showing a hyperdiploid content (DNA index greater than 1.05). The duration of complete remission was significantly longer in patients with distinct hyperdiploid DNA content (DNA index greater than 1.16) than in those with less hyperdiploid and diploid DNA content (DNA index less than 1.16). The results achieved by static cytophotometry were compared with flow cytometry analysis and with cytogenetic investigations of chromosomal abnormalities in leukemic cells. Higher correlation was found between flow cytometry and cytogenetics. Flow cytometry proved to be a more convenient method for detection of the DNA content in leukemic cells than static cytophotometry.

Determination of antineoplastic activity and toxicity of tumor necrosis factor (TNF) in animal experiments. Correlation to clinical findings.

Because of the deep evolutionary roots which macrophages and their products have, it should be possible to relate effects of the biological response modifier TNF observed in cancer patients with those determined in animal species. We have tested this hypothesis both with regard to antitumor efficacy and unwanted side-effects in murine tumor models. In the intramuscularly (i.m.) transplanted B16 melanoma, TNF had both after intratumoral (i.t.) and intravenous (i.v.) administration (qd 7-11, 14-17) a significant and dose-dependent effect on tumor growth. This effect was transitory and led only to a moderate increase in survival time of the animals. This correlates well with the also unsatisfactory clinical antineoplastic activity of TNF. From the measurement of body weight reduction, WBC counts, platelets, recalcification time, transaminases and body temperature in tumor bearing mice it can be concluded that there are close similarities to the side-effects observed in patients, although the level and/or time course of the noticed changes were differently expressed. In principle, it seems possible to predict clinical effects of biological response modifiers in animal experiments even if not all mechanisms are clearly understood.

Antimetastatic action of diltiazem on LS/BL tumor cells in liver tumor-colony assay.

Inhibition of experimental metastases of lymphosarcoma LS/BL cells by diltiazem, a calcium blocking agent, was tested. Diltiazem treatment (2 X 30 mg/kg p.o. for 12 days) resulted in a maximum of 72.8% inhibition of liver metastases. The authors suggest that diltiazem might become suitable candidate for antimetastatic treatment in humans.

Reductive effect of lonazolac on lung metastasis formation in mice.

The purpose of this study was to determine the antimetastatic potential of lonazolac. Intravenous inoculation of Lewis lung carcinoma (LLC) or melanoma B-16 (B-16) cells induced macroscopically detectable lung metastases on day 15 after inoculation. After pre- and post-treatment with lonazolac-Ca at oral doses of 1, 25, and 50 mg/kg, the numbers of animals with lung metastases and the score of metastases significantly decreased. Lonazolac-Ca had similar effects also on the formation of spontaneous lung metastases. After treatment with lonazolac-Ca at oral daily doses of 1, 25, and 50 mg/kg during 8 days (LLC) or 10 days (B-16) after inoculation of the tumor cells, the number of animals developing spontaneous lung metastases and the score of metastases also decreased. Intravenous injection of lonazolac natrium was effective in protecting the mice inoculated with 1 X 10(6) melanoma B-16 cells against acute pulmonary embolic death.

The effect of hyperthermia on the mouse testis.

The response of different stages of spermatogenesis to heat have been assessed by scoring the cell types in testis tubules at 14, 28 and 35 days after treatment. Deficiencies in spermatids at these times can be related back to the stage that the precursor would have been in 14 and 28 days earlier. On the 35th day the number of repopulated tubules was counted. The testes of CBA mice were heated using a radiofrequency equipment and controlled by a thermocouple in the other testis. Great difficulty was experienced in achieving a uniform temperature of 43 degrees C for a period of 30 minutes. The testes can be grouped into 2 categories: those with an appropriate heat profile and those which were overheated. The data showed that the weight of the testis at 14 days was only 65% of control and had slightly increased by 28 days to 88%. The number of sperm heads and late spermatids decreased to 33% at 14 days, but had increased to 88% by day 28. On the 35th day after heating to 43 degrees C cell depletion and shrinking of the tubules occurred. Sixty-four percent of examined tubules only had normal appearance and were repopulated. This shows that the temperature of 43 degrees C impairs the stem cells and it can be a warning to clinicians who think of applying hyperthermia for treatment of human tumors located in the testis area.

Malignant neoplastic disease in women.

This study refers to a longitudinal population study of women in Gothenburg, Sweden. The prevalences of malignant neoplastic disease in two cross-sectional studies in 1968-1969 and in 1980-1981, respectively, and incidence figures for the 12-year period between these cross-sectional studies are presented. The data on malignant neoplasms were based on interview of the participants in the population study, on information from the Cancer Registry of the Swedish National Board of Health and Welfare and from the Swedish National Bureau of Statistics and were confirmed by death certificates, inpatient and outpatient records and reexaminations of tissue specimens from the tumor tissue. The prevalences of malignant neoplastic disease increased with age from 0.3% at the age of 38 to 9.9% in women aged 60. The incidence rates during the 12-year period increased with age from about 2% in women aged 38 at the beginning of the study to be about 10% in women initially aged 60. Breast cancer was found to be the most common single malignant neoplasm followed by cancer of uterus and cancer of the ovaries.

Evaluation of carcinoembryonic antigen (CEA) and brain-type creatine kinase (CK-BB) in serum from patients with carcinoma of the lung.

The levels of carcinoembryonic antigen (CEA) and the activities of creatine kinase isoenzyme BB (CK-BB) were assessed in 84 patients with primary lung carcinoma and in 20 patients with nonmalignant lung diseases. The level of CEA was measured by the immunoenzymatic method using monoclonal antibodies (Abbott). The activity of CK-BB was assayed using a commercial kit (Boehringer Manheim, Monotest CK-NAC aktiviert). Increased levels of CEA were observed in 62% of patients, mostly in patients with nonsmall cell lung carcinoma (NSCLC), while enhanced activities of CK-BB were found in 39%, first of all in patients with small cell lung carcinoma (SCLC). A relationship was found between enhanced levels of CEA or CK-BB and the degree of carcinoma advance. The increased values of studied markers seem to indicate the limited possibility of surgical treatment and they are also important in prognosis after the resection of lung tissue.

Influence of recipients' immune status on effectiveness of adoptive immunotherapy with TAA specific T lymphocytes and interleukin-2 in CBA polyoma mice.

We investigated causes of failure of adoptive immunotherapy in 30% of tumor implanted CBA mice which were administered Il-2 and DTH mediating T lymphocytes. The lymphocytes were taken from polyoma implanted animals and restimulated in vitro with soluble polyoma TAA and Il-2. A close correlation was observed between the percentage of tumor implanted mice for whom the therapy was ineffective and the percentage of healthy mice with low immune response assessed in vitro by blastogenic response to ConA, PHA, and allogeneic lymphocytes. Il-2 administration was indispensable to complete tumor inhibition. The level of DTH to polyoma TAA in tumor implanted recipients was correlated neither with effectiveness of the therapy nor with immune status of the recipients, assessed by above criteria, and it was diminished by the Il-2.

Secondary neoplasms following cancer treatment with a special emphasis on lung tumors.

In patients with successfully treated Hodgkin's disease, lung cancers, and particularly small cell lung cancers, are not uncommon (relative risk: +/- 5) and result essentially from radiotherapy. What is usually considered as a late recurrence of small cell lung cancer occurs also frequently in long-term surviving patients after therapy for small cell lung cancer; it is hypothesized that at least some of these tumors might be in fact induced by the therapy used for the initial lung neoplasm.

Flow cytometric analysis of DNA content in focal nodular hyperplasia and hepatocellular carcinoma.

DNA index of twenty-three surgically removed, formalin-fixed and paraffin-embedded liver specimens (10 focal nodular hyperplasias--FNH, and 13 hepatocellular carcinomas--HCC) were studied by flow cytometry. Diploid value appeared in 9/10 FNH (one was hypodiploid), while 10/13 HCC (77%) had DNA aneuploidy (one hypo- and 9 hyperdiploid). The presence of normal DNA content in 3 HCCs suggests that DNA aneuploidy only cannot indicate the malignant transformation of a benign lesion (e.g. FNH).

Carcinoembryonic antigen and alpha-lactalbumin in phylloid tumor tissues.

The concentration of carcinoembryonic antigen and alpha-lactalbumin in tumor tissue cytosol were analyzed in a group of 19 tumors of cystosarcoma phyllodes type. Both antigens were also localized in the tissue of identical tumors by means of immunohistochemical procedure. The cytosol levels of both proteins were found to be higher in the histologically defined malignant type of phylloid tumors. This group was also characterized by the simultaneous occurrence of both antigens. We did not manage to prove any relationship between the presence of alpha-lactalbumin and the steroid hormone receptor positivity in tumor tissue.

A new variant of Rous sarcoma virus-33 nondefective, pathogenic for rats.

Rous sarcoma virus-33 (RSV-33) belongs to RSVs that have the least number of passages beyond its isolation from chicken tumor No. 1 among all current strains of RSV. Biological characterization indicated that it was pathogenic for rats. The results of the proviral restriction enzyme analysis showed that the established rat tumorigenic cell lines were the most likely infected by the same virus having a full-length genome.

Antigen capture assay for detection of bovine leukemia virus proteins by monoclonal antibodies.

A capture monoclonal antibody-based assay has been established for detecting the p24 core protein and the gp51 envelope glycoprotein of bovine leukemia virus (BLV). This assay is rapid, highly sensitive and specific. Viral antigens in test samples were identified using mouse monoclonal antibody-coated or microtiter plates by adding labeled monoclonal antibodies with different epitope specificities. The choice of an appropriate epitope specificity for the specificity of monoclonal antibodies was important for optimal performance of the assay. Results of this assay were in agreement with the syncytia induction assay routinely used for detecting BLV production by cells in vitro. The sensitivity of monoclonal antibody assay was 0.5 ng/ml for p24 and 1.25 ng/ml for gp51, respectively. The specificity was demonstrated by immunoblotting. The assay can be performed in a few hours, is simple, and is comparable with more time-consuming assays with regard to sensitivity and specificity.

Detection of human papillomavirus in cervical swabs from Indian women by cytological and immunocytochemical technique.

Cervical swabs were collected from 88 women in the age group of 17-55 years in Calcutta, India to study the prevalence of human papillomavirus (HPV) infection. The viral infection was demonstrated on the basis of koilocytotic changes in Papanicolaou staining (PAP test) and the presence of viral capsid antigen as detected by immunocytochemistry (IMC test). The PAP and IMC tests revealed 25% and 28.4% of women, respectively, to be positive for HPV infection. Higher frequency (61.1% to 87.5%) of infection was observed in moderate to severe dysplastic lesions. HPV infection was observed to be more frequent in the younger age group (less than 40 years) with 1-2 parity. Although koilocytes were absent in all (n = 51) of the apparently normal subjects, 4 (7.8%) of them were positive for HPV antigen. Except for these, sensitivity of PAP test and IMC test for the detection of HPV was found to be almost similar.

Heterogeneity of transplantable melanomas differing in the rate of growth and cellular differentiation in relation to their cell transglutaminase activity.

Transglutaminase activity has been investigated by the fluorescent method in cells of two transplantable melanoma lines of the same origin but differing in rate of growth and the degree of differentiation. Transglutaminase activity within the cells under examination was not the same. In comparison with the original melanotic line, the amelanotic melanoma line, less differentiated and growing faster, was characterized by a greater heterogeneity of cells with regard to transglutaminase activity, and it also displayed greater activity of the enzyme.

Aminopeptidases and angiotensin I-converting enzyme activities in primary human lung tumors and lung parenchyma.

The activities of alanyl aminopeptidase (AAP), arginyl aminopeptidase (RAP), alpha-glutamyl aminopeptidase (EAP) and angiotensin I-converting enzyme (ACE) were investigated in primary human lung tumors of different histological types and in matched lung parenchyma. In contrast to the studied aminopeptidases whose activity differences between tumor and lung tissues were infrequently significant, the activity of ACE was decreased highly significantly in the majority of lung tumors.

Detection of cancer metastases in regional lymph nodes: comparative histological and immunohistological investigations with the broad-range anticytokeratin monoclonal antibody A45-B/B3.

A total of 113 patients with carcinomas of breast, testis, stomach and colon were examined for lymph node metastases by means of an exact case-by-case comparison by conventional histology and by immunohistochemistry using the anticytokeratin monoclonal antibody A45-B/B3. Among 891 examined lymph nodes, 90% of metastases were recognized by both methods, about 2% by histology alone, and more than 10% by immunohistochemistry alone. The method can be applied for intraoperative frozen section diagnosis.

Asymmetric PCR-based strategy for genetic analysis of the p53 tumor suppressor gene in cell lines and tumor tissues.

A novel strategy for genetic analysis of the p53 tumor suppressor gene is described, based on direct sequencing of the asymmetric polymerase chain reaction (PCR) products. A set of 10 PCR primers was designed which allows to amplify and sequence highly conserved regions of the molecule, i.e. the target areas of p53 mutations. The stepwise optimization of RNA isolation, cDNA synthesis, PCR amplifications and sequencing resulted in a procedure which is faster and more reliable than the techniques used to search for p53 mutations so far. This and similar strategies should be applicable to the study of genetic alterations in antioncogenes or other classes of genes which suffer from subtle mutations potentially scattered along large segments of the molecule.

Serum antithrombin III and alpha-2-antiplasmin concentrations in patients with Hodgkin's disease in the course of chemotherapy.

Disturbances in hemostasis in cancer disease frequently occur. This clinical situation may contribute to the spread and metastasis of cancer. The determination of inhibitors controlling hemostasis especially during treatment may be of value for the evaluation of effectiveness of treatment and balancing of hemostasis. Twenty four patients diagnosed with Hodgkin's disease were introduced to our studies. The level of antithrombin III (AT-III) and alpha-2-antiplasmin (alpha-2-AP) in sera were determined before, during and after treatment with MOPP. We found decrease of AT-III concentration before treatment, and chemotherapy increased the level of this inhibitor but still below the level of control. Alpha-2-AP concentration was higher in patients and MOPP application decreased the level below the values found in controls. The determination of concentration of both inhibitors may be important for the evaluation of the effect of treatment in understanding how the disturbances of hemostasis may be equilibrated.

Molecular and biological properties of hamster tumor cell lines transformed with B77 virus: expression of v-src does not correlate with metastatic potential.

Three hamster tumor cell lines (B77Hep, B77H1De and ML cl 3.1) were investigated with the aim to determine some biological and molecular properties of cells which are connected with invasive and metastatic ability. Except B77H1De all cell lines exhibited high metastatic capacity in syngeneic adult animals. Analysis of cell lines revealed a relationship between metastatic ability and growth properties (growth rate, saturation density and colony formation in soft agar). Southern blot analysis of genomic DNA samples from high metastatic cell line (B77Hep) and low metastatic (B77H1De) showed that the metastatic potential of these cell lines did not depend on the number of integrated proviral copies. Northern blot analysis was used to determine the level of mRNA encoded by v-src gene in B77Hep and B77H1De cell lines. We found a good correlation between the number of integrated proviral copies and the level of v-src gene expression in investigated cell lines, but not with their metastatic potential. No proviral sequences were found in genomic DNA isolated from ML cl 3.1 cell line. In cell lines used in this study we found differences in expression of endogenous proto-oncogenes c-myc and c-fos.

Do some malignant melanoma cells share antigens with the myeloid monocyte lineage?

Melanoma cells freshly isolated from 63 advanced primary lesions and 103 metastases were analyzed by staining with monoclonal antibodies MEM 28 directed against a 200 kDa antigen present on all leukocytes and tissue macrophages (CD 45), MEM 18 directed against a monocyte antigen of 53 kDa, anti CD 14--Immunotech, Marseille and 3.9 directed against a 150 kDa antigen expressed on monocytes and to even greater degree on most tissue macrophages (CD 11 c). All antibodies showed variable reactivity with melanoma cells, percentage of positive tumor cells ranged from 0 to 70.

Effects of tissue fixation conditions and protease pretreatment on immunohistochemical performance of a large series of new anti-keratin monoclonal antibodies: value in oncopathology.

A comparative study with 21 recently raised monoclonal antibodies (3 of which are reported here for the first time) to human keratin polypeptides was performed on a wide range of paraffin-embedded tissues and tumors, aimed at the examination of effects of four different fixatives and protease pretreatment on the immunohistochemical detection of keratins. Our data demonstrated that: (a) formaldehyde-based fixatives modified by acidification and/or addition of methanol gave results superior to those achieved by routinely used formol saline; (b) relatively rare antibodies (4 out of 21) could be identified which gave reliable immunostaining patterns even on routine formalin-fixed material; (c) a proteolytic digestion step preceding the immunostaining was beneficial for the performance of the majority of antibodies in our panel. Additional options which could potentially lead to further improvement of keratin immunohistochemistry in paraffin embedded specimens are also suggested. This work provides the necessary basis for wider application of the anti-keratin antibodies of the C-series in both routine oncopathology and research-oriented retrospective studies.

High prevalence of circulating antibodies to MuLV p30 antigen in human sera. An autoimmune response?

To study the possible involvement of a murine leukemia virus (MuLV) related agent in human cancer, an extensive immunoblotting analysis of human sera (cancer, autoimmune as well as control normal ones) for the presence of antibodies to MuLV structural proteins was performed. Out of 350 sera, 89 reacted with gag precursor Pr65, 72 reacted with major viral core protein p30 and five with the matrix protein p15. Antibody reactivity to the env-encoded glycoprotein gp70 was detected in 7 cases out of 16 sera tested. There were no significant differences between pathological and normal sera concerning the patterns and the frequency of the reactivity. Sera from patients with various malignancies (mainly with breast cancer) generally displayed more intensive signals to MuLV p30 than normal sera. Epitope mapping revealed that MuLV p30-reactive antibodies recognize an antigenic determinant(s) located at the carboxyterminus of the protein.

Comparison of two non-cross-resistant combinations (ABVP/LOPP) with COPP plus bleomycin in the treatment of advanced Hodgkin's disease.

Eighty patients with advanced Hodgkin's disease were randomized either to treatment with combination of doxorubicin, bleomycin, vinblastine, and prednisone (ABVP), alternating with lomustine, vincristine, procarbazine, and prednisone (LOPP)--Group A, or to combination of cyclophosphamide, vincristine, procarbazine, prednisone, and low dose of bleomycin (COPP-Bleo)--Group B. Thirty-nine out of 41 patients (95%) in Group A achieved complete remission (CR) as compared to 25 CR in 39 patients (64%) in Group B. Patients with systemic symptoms, bulky disease, and nodular sclerosis achieved significantly more CR after treatment with ABVP/LOPP regimen than with COPP-Bleo regimen. Ninety percent of patients are alive in Group A (median observation time 97+ months) as compared to 58% in Group B (median observation time 97+ months). Ninety-two percent of complete responders are in CR in Group A as compared to 53% of complete responders in Group B. These differences between both groups are significant. More serious (WHO grade III and IV) myelosuppression as well as stomatitis and alopecia were observed in Group A. Gastrointestinal toxicity and neurotoxicity was more frequent in Group A. No patient died due to toxicity in Group A as compared to one patient in Group B. Non-cross-resistant alternating regimen ABVP/LOPP was more effective in the treatment of advanced Hodgkin's disease than the COPP-Bleo regimen, especially for patients with advanced Stage IVB Hodgkin's disease.

A new class of potential carcinogenesis inhibitors: hindered p-benzoquinones.

The investigation of the mechanisms of action by which phenolic antioxidants (i.e. BHA, BHT, etc.) protect DNA against interaction with activated BaP, led us to the finding that oxidated aminophenols are much more potent in this respect, being also powerful inhibitors of cytochrome P-450 dependent monooxygenases. However, the quinoneimine structures probably involved in this effect are chemically unstable reactive species and therefore difficult to handle. Based on these observations, we extended this study on several types of benzoquinones. We demonstrated that 2,6-di-t-butylbenzoquinone exerted a very good protective effect at DNA level (in standard conditions) as compared to the "classical" BHA (i. e. 91.3% and 34.4%, respectively). This hindered quinone is nontoxic (DL50 = 3085 mg/kg b. w.) and also did not exhibit inhibitory activity against GST. In contrast, the nonsubstituted p-benzoquinone is a powerful inhibitor of this last enzyme. Recently, 2,6-di-t-butylbenzoquinone was isolated from mutagenic depressing food and was considered one of the factors responsible for this effect.

Comparison of the effect of hydroxyurea and methotrexate on DNA fragmentation at various reaction conditions.

Using the changes in DNA breakage as a marker of DNA damage, the direct action of hydroxyurea (HU) and methotrexate (MTX) on DNA was examined. The experimental design was to expose isolated DNA to HU and MTX alone or HU and MTX with accelerators of free radical reaction (H2O2, Fe..) and to determine DNA fragmentation assessed by electrophoresis. The results indicated that HU can damage DNA, but to demonstrate this ability it needs H2O2, Fe.. or prolonged incubation in solution. Unlike HU, MTX with H2O2 was ineffective; MTX with Fe.. at certain degree protected DNA against lesions induced by Fe.. alone. It is concluded that despite several common features of HU- and MTX-induced toxic side-effects in the cells suggesting interference of these drugs with free radical reactions, their direct effect on DNA under oxidizing conditions is quite different at least at the concentrations used by us.

Effect of new purine analog 6-purinyl-N-[2-chloroethyl] thiocarbamate (Cloturin) on immune system of mice.

The effect of purine analog 6-purinyl-N-[2-chloroethyl] thiocarbamate (Cloturin) was studied in a battery of immunological tests in mice. Cloturin exhibited pronounced suppressive nonselective effect on immune system and its functional capacity. Cloturin decreased cellularity of spleen and bone marrow, elicited leukocytopenia in peripheral blood, suppressed phagocytosis, graft-versus-host reaction and specific antibody production. In comparison with azathioprine, Cloturin had more pronounced activity. The immunosuppressive effect of Cloturin on T-dependent specific antibody production suggests that Cloturin possesses both alkylating and antimetabolic properties. For its properties Cloturin could be useful not only as a cytostatic drug, but also as an immunosuppressive agent.

Response of human chronic myeloid leukemia cells to mitoxantrone cytotoxicity: potentiation by bepridil, a calcium channel antagonist.

The ability of bepridil, a calcium channel blocker, to potentiate the antitumor activity of mitoxantrone (MITO) in human chronic myeloid leukemia (CML) cells was evaluated. MITO and bepridil, when incubated alone with the CML cells for 4 h, indicated a dose-dependent increase in the inhibition of 3H-thymidine incorporation. Incorporation rate of the radiolabeled thymidine into DNA was used as a measure of cell growth. When the CML cells were exposed to MITO (1 microgram/ml) in the presence of bepridil (1 and 5 micrograms/ml), an enhancement in the inhibition of DNA biosynthesis was observed in 14 out of 17 human CML samples studied. This significant inhibition (p less than 0.001) of 3H-thymidine incorporation due to the combination was found to be completely irreversible. Bepridil was identified predominantly in the octanol phase in the octanol/water partitioning studies. This lipophilic property of drug response modulators was implicated in the observed increase in the intracellular uptake of anticancer drugs, which in turn led to an enhanced cytotoxicity correlating well with the MITO activity observed in this study. The results are suggestive of clinical utility of bepridil as an adjuvant to enhance the anticancer ability of MITO in the treatment of CML.