Search PubMed⌕ Search

Biomedical subjects

L Milas

Publications and source records attributed to L Milas.

At least 145 records · Page 8Linked to original sources
PubMed1986

N-methylformamide-mediated enhancement of in vitro tumor cell chemosensitivity.

The effects of the differentiation-inducing polar solvent N-methylformamide (NMF) on the in vitro response of murine hepatocarcinoma (HCa-1) cells to 1,3-bis(2-chloroethyl)-1-nitrosourea, cis-diamminedichloroplatinum (II), and melphalan were investigated using the sister chromatid exchange (SCE) and cell survival assays. When cells were exposed to 1.25% NMF, cell culture doubling time increased from 12 to 43 h and cell volume increased from 940 microns 3 to 1440 microns 3. Growth of HCa-1 cells in NMF for 96 h before drug treatment enhanced the SCEs induced by each of the three chemotherapeutic agents. For each drug, maximum enhancement occurred after 72 h of NMF pretreatment, and the enhancement was eliminated 48 h after NMF was removed. Pretreatment with 1.25% NMF for 96 h also enhanced the cell kill induced by each drug. NMF exposure modified primarily the low-dose shoulder region of each drug cell survival curve. The data indicate that NMF is an effective chemosensitizing agent for HCa-1 cells in vitro and suggest that NMF may provide clinical benefits when administered in combination with antineoplastic drugs.

Animals↗
PubMed1986

Potential methods for predicting tumor radiocurability.

Several predictors of tumor radiocurability are already integrated into clinical practice, for example, tumor size, gross morphology (that is, infiltrative or exophytic), histologic type and grade. These are nonspecific and relatively imprecise. The aim of research into predictive assays is not only to refine the discrimination of existing predictors, but also to suggest specific experimental approaches for overcoming tumor radioresistance in individual patients. Two broad categories of predictive assays can be defined: direct and indirect measurement of tumor cell survival and/or repair capability following irradiation, and measurement of cellular and extracellular parameters affecting radiosensitivity. The ongoing research at The University of Texas M. D. Anderson Hospital is overviewed to illustrate potential methods for predicting radiocurability.

Animals↗
PubMed1986

Protection of acute and late radiation damage of the gastrointestinal tract by WR-2721.

WR-2721 was investigated for its protective effect against acute and late damage produced by irradiation of the esophagus, small intestine, and colon of mice. The microcolony assay was used to measure the acute response of the small intestine and the colon, and an LD50 assay (within the 28- to 42-day time range) was used to measure acute esophageal damage. A dose of WR-2721 at 400 mg/kg, injected 30 min prior to irradiation, resulted in a protection factor (PF) of 1.6 against radiation damage in these three regions of the gastrointestinal tract. Lethality and histology scores were applied to determine late radiation damage to the rectum, at times ranging from 3 to 15 months after irradiation. Deaths occurred after doses of 20 Gy and above throughout the postirradiation period. WR-2721 increased the survival of mice; the PF calculated from the LD50 values was 1.5. PFs of animal survival did not vary during the observation period. Histological studies showed evidence of ulceration, fibrosis, and vascular changes as late radiation damage. WR-2721 protected against radiation-induced histological damage with a PF of 1.3. There was no qualitative difference between the types of histological damage observed in the group undergoing only irradiation and the group treated with WR-2721. Biochemical measurements of fibrosis by hydroxyproline determination of collagen 16 months after irradiation showed an increase in collagen per milligram wet weight of rectal tissue in all irradiated groups, but no increase in the amount of collagen per 5 mm segment of the rectum. Thus it appears that the apparent fibrosis is a result of atrophy rather than collagen accumulation. We conclude that WR-2721 is indeed effective at protection against late damage from large single doses of radiation to the rectum as measured histologically and also improves the long-term survival of the mice, although the target cells for this damage are not known.

Animals↗
PubMed1986

Effect of the radiosensitizer misonidazole and the radioprotector diethyldithiocarbamate on spontaneous metastasis formation of murine tumors.

The effect of treatment with the hypoxic cell radiosensitizer misonidazole (MISO) and the radioprotector diethyldithiocarbamate (DDC) on the formation of spontaneous lung metastases of four different spontaneously metastasizing murine tumors was investigated. The tumors were mammary carcinoma MCA-K, hepatocarcinoma HCA-1, and sarcomas SA-4020 and SA-NH. Multiple daily treatments with MISO significantly enhanced the incidence of metastases only in MCA-K. Because only MCA-K, but not the three remaining tumors, is immunogenic, the treatment with MISO may be associated with the promotion of metastasis primarily in the immunogenic tumors. Treatment of mice with DDC had no influence on metastatic spread. However, when given prior to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), DDC reduced BCNU-induced enhancement of HCA-1 metastases.

Animals↗
PubMed1986

Treatment of experimental lung metastasis with local thoracic irradiation followed by systemic macrophage activation with liposomes containing muramyl tripeptide.

The purpose of these studies was to determine whether the combination of a low-dose local thoracic irradiation (LTI) followed by systemic activation of macrophages with liposomes containing muramyl tripeptide phosphatidylethanolamine (MTP-PE) would significantly decrease established experimental fibrosarcoma lung metastases. Male C3Hf/Kam mice were given i.v. injections of 1 X 10(5) fibrosarcoma cells. Five days later, groups of mice were treated with saline, with 8 Gy LTI, or with liposomes containing MTP-PE or first with 8 Gy LTI and followed by multiple i.v. injections of liposomes containing MTP-PE. Most of the mice in the groups treated with liposomes died by day 42 of the experiment. In contrast, 60% of the mice treated with the combination of LTI and liposomes containing MTP-PE were alive by day 140 of the study. These mice were killed and were found to be free of tumors. Control studies demonstrated that liposomes administered i.v. to mice given LTI were trapped in the capillary bed of the lungs and activated the tumoricidal properties of lung macrophages. We conclude that, in this combination, low-dose LTI, which can lead to both tumor cell death and inflammatory changes in the lung capillaries, could precede i.v. administration of liposomes containing MTP-PE. This combination of treatments can lead to destruction of tumor foci in the lung that cannot be achieved with either treatment alone.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1986

Retardation of tumor growth in mice caused by radiation-induced injury of tumor bed stroma: dependency on tumor type.

Dependency on tumor type of tumor growth retardation caused by the radiation-induced damage of tumor bed stroma, a phenomenon known as the tumor bed effect (TBE), was investigated using two mammary carcinomas designated MCA-4 and MCA-K and two fibrosarcomas designated FSA and NFSA, all syngeneic to C3Hf/Kam mice. Inoculations of tumor cells were given s.c. into the right hind thighs of mice either treated or not treated 1 day earlier with graded doses of gamma-rays; tumor latency and growth rate were determined. Tumor latency was prolonged and tumor growth was retarded, but the magnitude of these two features of TBE greatly depended on radiation dose and tumor type. TBE began to appear at doses of 5-10 Gy and then sharply increased as the dose of radiation was increased up to between 20 and 30 Gy, at which point a plateau was achieved. TBE was also significant after 40 and 60 Gy total dose given in daily fractions of 2 Gy 5 times per week, a schedule commonly used in radiotherapy treatment of cancer patients. Carcinomas exhibited more pronounced TBE than fibrosarcomas, with NFSA showing only minimal TBE. Radiation-inactivated MCA-4 and FSA cells admixed with viable MCA-4 cells reduced tumor latency, but not the tumor growth delay, of resulting MCA-4 tumors in preirradiated legs. In contrast, admixture of irradiated NFSA and viable MCA-4 cells abolished growth delay but did not influence tumor latency of the TBE phenomenon. Thus the type of a tumor growing in the irradiated tissue is a very important factor that determines the expression of TBE.

Animals↗
PubMed1985

Modification of tumor response to cyclophosphamide and irradiation by preirradiation of the tumor bed: prolonged growth delay but reduced curability.

The effect of tumor bed irradiation (TBX) on subsequent tumor response to treatment with cyclophosphamide (CY) or further irradiation was studied in mice. Using the growth delay assay, the therapeutic response was enhanced by prior TBX: for example, in mice receiving 3000 rad TBX 1 day before fibrosarcoma cell inoculation, the growth delay from 8 to 12 mm produced by CY (150 mg/kg) was 18.8 days compared with 9.4 days without prior TBX. This effect was independent of time between TBX and tumor cell inoculation over the range 1-56 days. When tumor cure experiments were performed, however, the effect of prior TBX was to decrease significantly the proportion of tumors controlled by either CY or irradiation and to make the dose-response curve for radiocurability less steep. These data are best interpreted by postulating that TBX increases the environmental heterogeneity of tumors growing in preirradiated sites, with an overall net decrease in the cell kill achieved by a given dose of CY or radiation. This results in increased resistance to cure and a lack of dose response. However, the TBX also causes slower regrowth of surviving cells, so that an increase in tumor growth delay is realized. Thus, although eradication of postirradiation recurrences by chemotherapy is compromised, their palliation may actually be enhanced.

Animals↗
PubMed1985

Relationship between lymph nodal status and primary tumor control probability in tumors of the supraglottic larynx.

A retrospective review of 248 patients with squamous cell carcinoma of the supraglottic larynx was undertaken to determine the relationship between the probability of control of the primary lesion, the extent of neck nodal disease at initial presentation, and its ultimate control. All patients were treated at the U.T. M. D. Anderson Hospital between 1960 and 1980, and had a minimum of 3 years follow-up. The primary lesion was staged T1 in 38 patients, T2 in 132, T3 in 50 and T4 in 28. The initial volume of neck nodal disease was scored on a scale of 0 (no palpable nodes) to 9 (bilateral neck nodes greater than 6 cm in diameter). All primary lesions were treated definitively with megavoltage radiation therapy. Treatment to the neck varied according to the extent of lymph node involvement. There was no significant difference in the range of total radiation doses delivered to the primary lesion, stage for stage, in patients who presented with clinically negative or positive nodes, or in those with controlled versus uncontrolled neck disease. Analysis of the probability of primary tumor control was made by life table methods because of the poorer survival expectation in node positive patients. For T1 and T2 primary lesions, any positive node decreased the probability of primary tumor control (p = 0.06). For T3 and T4 lesions, a single node less than 3 cm in diameter did not worsen the chance of primary tumor control, but any greater degree of lymph node involvement did (p = 0.03). For both T stage groupings, the probability of primary tumor control at 5 years decreased progressively with increasing neck nodal disease. Primary tumor control probability was also significantly associated with control of the neck disease, independent of the modality of neck treatment. No correlation could be demonstrated between the histological grade of the primary tumor and initial lymph node status or tumor control probability. Possible interpretations of this manifestation of biological heterogeneity are discussed.

Biopsy↗
PubMed1985

Prediction of in vivo tumor response to chemotherapeutic agents by the in vitro sister chromatid exchange assay.

The ability of the in vitro sister chromatid exchange (SCE) assay to predict in vivo tumor drug sensitivity was investigated using a spontaneous hepatocarcinoma in C3Hf/Kam mice and 3 chemotherapeutic agents: melphalan; cis-platinum; and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). For hepatocarcinoma cells grown in monolayer culture, melphalan was the most efficient at inducing SCEs, and BCNU, the least. cis-Platinum induced a range in SCEs that overlapped those of BCNU and melphalan, suggesting that hepatocarcinoma is not a homogeneous population with intermediate sensitivity, but is a mixture of cis-platinum-sensitive and -resistant cells. According to in vitro cell survival curves, hepatocarcinoma was most sensitive to melphalan, less sensitive to cis-platinum, and essentially resistant to BCNU. The relative antineoplastic effects of melphalan, cis-platinum, and BCNU in vivo were compared by the response of artificial and spontaneous pulmonary metastases and solid tumors to these agents. For artificial metastases, there was a dose-dependent decrease in the number of lung nodules in mice treated with melphalan or cis-platinum, with melphalan being the more effective. BCNU had no effect. Spontaneous pulmonary metastases generated from hepatocarcinoma leg tumors were reduced in those mice treated with melphalan, unaffected by cis-platinum, and increased by BCNU. In hepatocarcinoma leg tumors (5 to 6 mm in diameter), melphalan induced the longest growth delay, and BCNU the least. Therefore, the relative effects produced by these three drugs in vivo were the same as predicted by SCE induction in vitro. The SCE assay may thus have potential clinical application.

Animals↗
PubMed1984

Tumor sensitizing effect by misonidazole in a clinically relevant radiation dose range.

The survival of cells from two murine fibrosarcoma (FSa) subpopulations after exposure to radiation only or radiation in combination with misonidazole (0.2 mg/g/fraction) was determined using a lung colony assay. FSa tumors grown in the hind legs of C3Hf/Kam pathogen-free mice were irradiated in situ when the tumors were 8 to 10 mm in diameter. Single cell suspensions prepared from excised tumors were separated on linear density gradients of Renografin, and the clonogenicity of predominantly oxic Band 2 (density 1.08 g/cm3) and predominantly hypoxic Band 4 (density 1.14 g/cm3) cells were measured. The surviving fraction of cells after doses of 1, 2, and 3 Gy, alone or preceded 30 minutes earlier with an i.p. injection of misonidazole (0.2 mg/g) was estimated from that measured after total radiation doses of 5 Gy = 5 X 1 Gy, 10 Gy = 5 X 2 Gy, and 15 Gy = 5 X 3 Gy, with the misonidazole-treated groups receiving a total drug dose of 1 mg/g, under the assumption of an equal effect per fraction. Under these conditions the initial slopes of Band 2 cells following irradiation only or irradiation plus misonidazole were 1D0 = 3.6 Gy and 2.74 Gy, respectively, giving rise to a sensitizer enhancement ratio of 1.3. Band 4 cells exhibited a 1D0 of 5.15 Gy to radiation only and 2.75 Gy to radiation plus misonidazole (SER of 1.9). In addition, misonidazole when administered alone in a single dose or up to 5 fractions of 0.2 mg/g each separated by 4-hour intervals, was effective in killing 50% of the Band 4 cells. The target population at risk appeared to remain constant regardless of the number of dose fractions administered. In contrast, Band 2 cells were not affected by the cytotoxic action of misonidazole. These data suggest that misonidazole is effective in sensitizing hypoxic cells in the clinical dose range, and that it is directly cytotoxic to hypoxic tumor cells.

Animals↗
PubMed1984

Protection of spermatogonial survival and testicular function by WR-2721 against high and low doses of radiation.

The radioprotection of normal cells with WR-2721 at doses of radiation extending down to less than 1 Gy was investigated using testicular cells. Survival of stem spermatogonia after single doses of radiation was measured by counts of repopulating tubules and by sperm head counts, with consistent results obtained for both endpoints. Protection factors (PF) obtained by injection of 400 mg/kg WR-2721 at 15 min prior to irradiation decreased from about 1.4 at radiation doses above 10 Gy to 1.0 at 2 Gy. Similarly, the radioprotection by 300 mg/kg WR-2721 was reduced from a PF of about 1.35 when the drug was given prior to a single high dose of radiation to 1.0-1.1 when the drug was given prior to each of 5 daily fractions of 2 Gy. Thus, less protection of testicular stem cells by WR-2721 was observed at lower doses of radiation. This lowered protection may be explained, at least in part, by a direct cytotoxic effect of WR-2721 on testicular stem cells. Protection of differentiated spermatogonia was observed with 400 mg/kg WR-2721; the PF was 1.4 at 1 Gy and decreased at lower doses. The protection of testicular function by WR-2721, as assayed by the return of fertility and the maximum recovered level of sperm production, was compared to the protection of stem cell survival. At about 8 Gy the PF with 400 mg/kg WR-2721 for both functional endpoints was about 1.5, which was not significantly different from the value of 1.3 obtained using the stem cell assays.

Amifostine↗
PubMed1984

Modification by dexamethasone of radiation response of in vitro cultured cells.

Because of the potential clinical significance of the report that dexamethasone is a radioprotector of Chinese hamster V-79 cells, the effect of dexamethasone treatment on the radiosensitivity of five other cultured mammalian cell lines (including two human cell lines) was tested and preliminary investigations into the mechanism of protection of V-79 cells were undertaken. In agreement with the published results of others, we found that treatment of V-79 cells with dexamethasone results in a 1.3-fold increase in D0. Conversely, dexamethasone had no effect on the radiosensitivity of Chinese hamster ovary cells, murine fibrosarcoma, rat glioma cells, human diploid fibroblasts, or human mammary carcinoma cells. To study the mechanism of the radioprotective effect of dexamethasone on V-79 cells, the cell cycle was examined. Dexamethasone treatment causes a change in cell cycle distribution in V-79 cells, resulting in a dose-dependent reduced fraction of S-phase and an increased fraction of G1- and G2 + M-phase cells. However, these kinetic changes cannot explain the observed radioprotection of asynchronous populations, since purified G1 cells are more radiosensitive. Furthermore, cells synchronized in G1 by centrifugal elutriation were shown to be protected by dexamethasone to the same extent as was the unsorted population, thereby ruling out the mechanism of protection being a redistribution in the cell cycle.

Animals↗
PubMed1984

In vivo radioprotective activities of diethyldithiocarbamate (DDC).

Studies were performed to determine whether diethyldithiocarbamate (DDC) protects against radiation damage to bone marrow, jejunal crypts, testicular tubules, hair follicles, tissues in the leg responsible for leg contractures, and a fibrosarcoma (FSA) of C3Hf/Kam mice. In most experiments, DDC at a dose of 400 mg/kg or 1000 mg/kg body weight was given i.p. 30 minutes before single doses of gamma radiation. DDC (1000 mg/kg) given 30 minutes before whole-body irradiation protected hematopoietic stem cells by a factor (PF) of 1.59, as assessed by the LD50/30 assay, and by PFs of 1.32-1.55, as assessed by the endogenous spleen colony assay. A dose of 400 mg/kg DDC was less effective. Protection was also significant against hair loss and leg contractures; PFs produced by 1000 mg/kg DDC were 1.44 and 1.38-1.51, respectively. Jejunum was protected by 400 mg/kg DDC (PF = 1.2), but not by 1000 mg/kg. The opposite was observed with testis: 1000 mg/kg was protective (PF = 1.2), but not 400 mg/kg. DDC also protected the FSa tumor, either as lung micrometastases or as a solitary tumor in the leg. Both 400 mg/kg and 1000 mg/kg DDC protected 4 day-old micrometastases by a PF of approximately 1.1. DDC at a dose of 1000 mg/kg protected 8 mm leg tumors by a PF of 1.24 at the TCD50 level. Therefore, DDC protected both normal tissues and FSA, but the degree of protection varied greatly. A therapeutic gain was achieved in some instances.

Animals↗
PubMed1984

Effect of tumor type, size, and endpoint on tumor radioprotection by WR-2721.

Experiments are reported showing that the degree of tumor radioprotection afforded by WR-2721 varies with the type of tumor and assay endpoint, and that for a given tumor system, microaggregates are protected better than larger cell masses. The tumors used were a methylcholanthrene-induced fibrosarcoma (FSa), and two tumors of spontaneous origin, another fibrosarcoma (NFSa), and a mammary carcinoma (MCa-4), all syngeneic to C3Hf/Kam mice. WR-2721 was given in a dose of 400 mg/kg 30 minutes before irradiation in all experiments. In TCD50 assays, WR-2721 protected 5 mm diameter and impalpable 3 day-old transplants of 5 X 10(5) FSa cells growing in the leg by factors of 1.11 and 1.13, respectively. Using the tumor latency endpoint, 3 day-old s.c. transplants of 10(3) FSa in the abdominal wall were protected by a factor of 1.27, a degree of protection similar to that reported earlier for sterilization of lung micrometastases of the same tumor. MCa-4 tumors growing in the leg were protected better than FSa in TCD50 assays with protection factors of 1.3 for 4 day-old transplants, 1.24 for 5 mm tumors, and 1.23 for 8 mm tumors. MCa-4 tumors recurrent after irradiation as 4 day-old transplants grew more rapidly in mice that had received WR-2721, and this was shown to be most likely due to protection by the drug against expression of the tumor bed effect. Using the lung micrometastases assay, NFSa was protected by a factor of 1.22. This variability in protection with different tumor types, sizes, and assay endpoints is discussed in terms of drug delivery and uptake, and also in relation to the influence of tumor hypoxia on the radioprotective ability of WR-2721.

Amifostine↗
PubMed1984

Cytotoxic effects of WR-2721 on mouse testicular cells.

WR-2721 (S-2-(3-aminopropylamino)ethylphosphorothioic acid) has been demonstrated to be cytotoxic to stem spermatogonia in the mouse. Five and 10 injections of 300 mg/kg killed sufficient numbers of stem cells to reduce sperm production 56 days after treatment by 16 and 43%, respectively. Single injections of 300 or 400 mg/kg of WR-2721 given 15 min after irradiation produced negligible toxicity to stem cells as measured by counts of repopulated tubules; 600 mg/kg reduced stem cell survival by 47%. Four daily injections of 300 mg/kg given 4, 3, 2, and 1 days prior to irradiation (with or without a fifth injection 15 min after irradiation) reduced stem cell survival by about 60%. The cytotoxic effects of WR-2721 on testicular stem cells at least partially explains the reduced protection factors observed in the testis with low doses of radiation and during fractionated treatments involving multiple injections of drug.

Amifostine↗
PubMed1984

DNA damage produced by combined hyperglycemia and hyperthermia in two mouse fibrosarcoma tumors in vivo.

In this study we used alkaline elution to examine DNA damage produced in two murine fibrosarcomas after hyperthermia (42 degrees C), with or without preinduced hyperglycemia. The work was stimulated by a recent report that pretreatment of mice with glucose prior to hyperthermia decreased the growth rate in a similar fibrosarcoma tumor. The intercellular tumor pH dropped from its resting value of 7.1 to a value of 6.6 at 1.5 hr after a single injection of glucose. While treatment with either glucose alone or heat alone produced very little detectable damage, the combination of these two agents resulted in marked degradation of tumor DNA isolated immediately after treatment. DNA degradation was accompanied by a simultaneous decrease in cell viability; thus, direct cell killing and subsequent nuclease or lysosomal enzyme activity are probably involved. We also tested whether hyperglycemia combined with hyperthermia influenced the DNA-DNA crosslinking induced by subsequent cyclophosphamide (Cy) treatment. Because of the extensive degradation caused by the pretreatment alone under the conditions used in these initial experiments, we were not able to quantitate with validity the amount of Cy-induced crosslinking. However, damage in viable cells may presumably interact with the subsequent Cy treatment to produce further selective cell killing in the tumor.

Animals↗