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Biomedical subjects

G Gallagher

Publications and source records attributed to G Gallagher.

At least 73 records · Page 4Linked to original sources
PubMed1991

Synthesis of water-soluble (aminoalkyl)camptothecin analogues: inhibition of topoisomerase I and antitumor activity.

Water-soluble analogues of the antitumor alkaloid camptothecin (1) were prepared in which aminoalkyl groups were introduced into ring A or B. Most of the analogues were prepared by oxidation of camptothecin to 10-hydroxycamptothecin (2) followed by a Mannich reaction to give N-substituted 9-(aminomethyl)-10-hydroxycamptothecins (4-12) or by subsequent modification of Mannich product 4 (13, 15, 17, 19, 21). Others were obtained by modification of the hydroxyl group of 2 (25,26) or by total synthesis (35,42,43). These analogues, as well as some of their synthetic precursors, were evaluated for inhibition of topoisomerase I, cytotoxicity, and antitumor activity. Although there was not a quantitative correlation between these assays, compounds that inhibited topoisomerase I were also cytotoxic and demonstrated antitumor activity in vivo. Further evaluation of the most active water-soluble analogue led to the selection of 9-[(dimethylamino)methyl]-10-hydroxycamptothecin (4, SK&F 104864) for development as an antitumor agent. In addition to its water solubility, ease of synthesis from natural camptothecin, and high potency, 4 demonstrated broad-spectrum activity in preclinical tumor models and is currently undergoing Phase I clinical trials in cancer patients.

Animals↗
PubMed1991

Multiple epitopes of the human ovarian cancer antigen 14C1 recognised by human IgG antibodies: their potential in immunotherapy.

We have defined a novel ovarian cancer-associated membrane antigen, 14C1, using human monoclonal antibodies derived by EBV-transformation of in situ sensitised patients' B-cells. The pattern of recognition of this antigen by these antibodies suggests that at least three epitopes are discernable. These antibodies can be used to promote the in vitro killing of ovarian cancer cells by activated macrophages and cytokines, implying a role for this antigen in the immunotherapy of ovarian malignancies. Evidence is presented that the 14C1 antigen may have some transmembrane signalling function.

Adult↗
PubMed1991

14C1, an antigen associated with human ovarian cancer, defined using a human IgG monoclonal antibody.

We have selected a human EBV-transformed cell line from the involved lymph nodes of an ovarian cancer patient which secretes an IgG1 kappa antibody, able to recognize an antigen present on the surface of ovarian cancer cells. The antigen, termed '14Cl,' has previously been shown by immunohistological techniques to be present on the surface of the malignant cells within tumour specimens. Western blotting analysis has shown that the majority of primary ovarian cancer specimens and three continuous cell lines derived therefrom express 14Cl; other tissue types were negative. Preliminary biochemical characterization has been carried out, which shows that the 14Cl antigen has a molecular weight range of 25-32 kD and an isoelectric point from pI 6.3 to 6.8. We believe that the 14Cl antigen is immunologically relevant to ovarian cancer patients and may therefore represent a novel target for both active and passive immunotherapy.

Antibodies, Monoclonal↗
PubMed1991

New Zealand black mice are immunologically resistant to high-dose, but not low-dose Leishmania mexicana infection.

The course of infection following s.c. inoculation of a wide dose range of L. mexicana stationary-phase promastigotes (SPP) was examined in sexually mature and immature NZB mice of both sexes. Infection with a high dose (greater than 10(7) SPP) was able to induce a protective in vivo response, which could be adoptively transferred with parasite-immune T cells, into naive, syngeneic recipients. In contrast, s.c. infection with a low dose (less than 10(7) SPP) induced non-healing lesions; disease susceptibility could also be transferred into naive animals with T cells from non-immune donors. When the ability to mount a delayed-type hypersensitivity (DTH) reaction was tested in these two groups, the high-parasite dose group gave a significantly higher response. The in vivo protection and high DTH response were reflected in the ability of cells derived from the high-dose resistant (but not low-dose susceptible) mice to mount an antigen-specific T cell response in vitro. The possible immunological effector mechanisms underlying high-dose resistance and low-dose susceptibility are discussed.

Animals↗
PubMed1991

Lymphokine-activated killer (LAK) cells modulate the effects of IL-2 on a T cell-mediated immune response.

The ability of LAK cells and/or IL-2 to affect the course of an established T cell response was examined in a delayed-type hypersensitivity (DTH) model. IL-2 greatly increased the magnitude of the response at 24 h, while LAK cells alone had no effect. The administration of LAK cells and IL-2 together also had no effect on the magnitude of the DTH response, demonstrating that LAK cells were able to remove the enhancement seen with IL-2 alone. The presence of LAK cells reduced the serum half-life of IL-2 significantly, but not to an extent able to account for the observed loss of IL-2 induced DTH enhancement. IL-2 administration influenced cell phenotypes in the spleen and draining lymph nodes (DLN), as well as increasing splenic weight; the additional presence of LAK cells markedly altered these effects of IL-2 in the spleen (but not the DLN). Taken together, these results suggest that LAK cells interact with activated T-cells within the immune system and modulate their function.

Animals↗
PubMed1991

Enhancement of a delayed hypersensitivity reaction to a contact allergen, by the systemic administration of interleukin-2.

The immunopharmacological effects of interleukin-2 (IL-2) on the sensitization and effector phases of the delayed-type hypersensitivity (DTH) reaction were studied using contact sensitivity to the haptenizing agent dinitrochlorobenzene (DNCB). When administered at the time of priming to DNCB, IL-2 had no effect on the subsequent magnitude of the response. Interleukin-2 was, however, able to increase the magnitude of the response when given at the time of secondary challenge; the degree of change was directly related to the dose of IL-2. The proportions of T cells in the draining lymph node and spleen of IL-2-treated animals decreased by approximately one-third, but there was no alteration to the balance between CD4+ and CD8+ T cells. The results suggest that the increase in DTH observed was due to a pharmacological effect rather than to an increase in T-cell number.

Allergens↗
PubMed1990

Interleukin-6 enhances the induction of human lymphokine-activated killer cells.

Human peripheral blood mononuclear cells develop a powerful lytic capacity when cultured in vitro with interleukin-2 (IL-2), becoming lymphokine-activated killer cells (LAK cells). As part of an investigation into means of influencing this process, the effect of other cytokines has been examined. In this study we describe the ability of interleukin-6 (IL-6) to regulate the induction and function of human LAK cells. The results show that substitution of IL-6 for IL-2 did not lead to the development of functional LAK cells, nor was IL-6 able to alter the lytic capacity of established LAK cells. However, when IL-6 was included with IL-2 during the induction phase of the LAK cells, the resulting cells displayed considerably greater lytic activity than those prepared with IL-2 alone. This effect was IL-6 dose-related. These results indicate that LAK cell development may be positively regulated in vitro; the implications of this observation for the clinical usage of LAK cells are discussed.

Cells, Cultured↗
PubMed1989

Detection of Ki-ras messenger RNA in normal and chemically transformed hamster oral keratinocytes.

The cheek pouch of the Syrian hamster is an excellent model for the experimental study of oral carcinogenesis. The carcinogenic chemical 7,12-dimethylbenz[a]anthracene consistently produces epidermoid carcinomas in the cheek pouch of the Syrian hamster, giving rise to characteristic histopathological lesions in a time-dependent manner. We now present experimental evidence that c-Ki-ras mRNA can be detected in all 7,12-dimethylbenz[a]anthracene-induced tumors examined (in vivo and in vitro) in this experimental oral cancer model while no detectable c-Ki-ras mRNA can be found in the normal hamster cheek pouch epithelium. Cellular synchronization experiments using a cell line (hamster cheek pouch carcinoma cell line 1) derived from one of these 7,12-dimethylbenz[a]anthracene-induced hamster oral tumors revealed that the c-Ki-ras protooncogene is expressed during the G1 phase of the cell cycle (proliferation dependent). Serum starvation and RNA synthesis inhibition experiments using hamster cheek pouch carcinoma cell line 1 cells suggest that the c-Ki-ras protooncogene is indeed quiescent in the normal hamster cheek pouch epithelium and that failure to detect its mRNA is not related to the slower proliferation of the normal epithelial cells. These results suggest that the transcription of the c-Ki-ras protooncogene is associated with malignant transformation in the cheek pouch of the Syrian hamster.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

The induction of protective immunity to Leishmania major in the BALB/c mouse by interleukin 4 treatment.

The ability of interleukin 4 (IL4), administered subcutaneously around the cutaneous lesion in the form of hydrophilic gels, to affect the development of established Leishmania major infections in the BALB/c mouse was studied. IL4 had a therapeutic effect on L. major lesion growth compared with control mice, causing not only resolution of the parasite lesions over a period of 10 weeks but also rendering animals resistant to reinfection. Adoptive transfer of splenic T cells, obtained from IL4-treated animals, conferred significant resistance to L. major infection in naive BALB/c mice compared with controls. These results demonstrate that IL4 is capable of not only reversing the usual (i.e. non-curing) course of L. major infection in the BALB/c mouse, but also of promoting the generation of protective immunity. The nature of the gel used to deliver the cytokine was found to be important since the therapeutic activity of IL4 in poloxamer gel was not observed when a hydroxypropylmethyl cellulose (hypromellose) gel was used as the IL4 vehicle.

Animals↗
PubMed1989

Modification of the hydroxy lactone ring of camptothecin: inhibition of mammalian topoisomerase I and biological activity.

Several camptothecin derivatives containing a modified hydroxy lactone ring have been synthesized and evaluated for inhibition of topoisomerase I and cytotoxicity to mammalian cells. Each of the groups of the hydroxy lactone moiety, the carbonyl oxygen, the ring lactone oxygen, and the 20-hydroxy group, were shown to be critical for enzyme inhibition. For example the lactol, lactam, thiolactone, and 20-deoxy derivatives did not stabilize the covalent DNA-topoisomerase I complex. With a few exceptions, those compounds that did not inhibit topoisomerase I were not cytotoxic to mammalian cells. Two cytotoxic derivatives that did not inhibit topoisomerase I were shown to produce non-protein-associated DNA single-strand breaks and are likely to have a different mechanism of action. One of these compounds was tested for antitumor activity and was found to be inactive. The present findings, as well as other reports that the hydroxy lactone ring of camptothecin is critical for antitumor activity in vivo, correlate with the structure-activity relationships at the level of topoisomerase I and support the hypothesis that antitumor activity is related to inhibition of this target enzyme.

Animals↗
PubMed1989

Phenotypic and cellular changes associated with loss of antigen-induced function in Epstein-Barr virus-specific human T-cell hybrids.

Human T-cell hybrids were constructed from the HAT-sensitive human T-cell line 'JMAE' and an uncloned population of T cells from donor SW (SW-T; partner cell) known to have strong specificity for the autologous Epstein-Barr virus (EBV)-transformed B cell, SWEBV. The resulting hybrids, 1A9, 1D12 and 2C8 were shown to have similar specificity and to increase their rate of proliferation in response to SWEBV. Furthermore, the hybrids responded to other suitable EBV-transformed targets, in an major histocompatibility complex-restricted manner. Continued study of these cells revealed that they were functionally, phenotypically and chromosomally unstable. The present report details the loss of specific function and the associated changes in cell-surface markers, chromosome number and basal proliferation rate.

Antigens, Viral↗
PubMed1989

Ability of alpha (but not beta) form interleukin-1 to support DNA synthesis in human tonsillar B cells.

The ability of the two forms of recombinant human interleukin-1 (alpha and beta) to support DNA synthesis in human tonsillar B cells was assessed. The results suggested that in two out of three cases the alpha form was able to support DNA synthesis when the beta form was not. These results support the hypothesis that each form of human interleukin-1 has a different role in supporting the growth of human B cells.

B-Lymphocytes↗
PubMed1989

Human lymphokine-activated killer cells develop syngeneic killing ability.

Lymphokine-activated killer (LAK)-cell therapy has emerged as a new strategy in designing protocols for the treatment of cancer. However, in its present clinical form, it has not fulfilled the early promise shown in murine models of human metastatic disease. In an attempt to gain understanding as to why this might be the case, we measured the ability of human LAK cells, generated in vitro for 4 days, to kill LAK cells from the same donor that had been exposed to IL-2 in vitro for 8 days, and vice versa. In eight separate experiments using different donors, 4-day ('early') LAK cells were able to kill syngeneic 8-day ('late') LAK cells, while late LAK cells were also able to kill early LAK cells. Strong killing was observed in both directions, which was almost total in one instance. In order to assess the development of this phenomenon, early LAK cells were tested for their ability to kill syngeneic LAK cells that were 1, 2, 3 or 4 days 'older' and the reciprocal experiment conducted using late LAK cells as effectors. The results illustrate a strong capacity for the development of syngeneic killing by human LAK cells. The possible implications of this phenomenon for the clinical administration of LAK cell/IL-2 therapy are discussed.

Cells, Cultured↗
PubMed1988

Evidence that interleukin 2 actively promotes both cell division and immunoglobulin secretion in human B cells.

Three human Epstein-Barr virus transformed B cell lines were seeded at densities below their capacity for autostimulatory growth and exposed to recombinant human interleukin 2 (IL-2). IL-2 was found to stimulate DNA synthesis in all three lines, and the level of immunoglobulin secreted was also greatly increased. The experiments were repeated, but in this case the final cell numbers were established by the MTT method and the immunoglobulin secreted per 1,000 cells calculated. Both of these parameters were significantly elevated, indicating that the higher immunoglobulin levels recorded were due to the rate of secretion having been actively increased by IL-2 and were not merely artifactual, resulting from increased cell growth. Thus, IL-2 can actively promote DNA synthesis and cell division and can also increase immunoglobulin secretion in human B cells.

Antibody Formation↗
PubMed1988

Interleukin-3 and interleukin-4 each strongly inhibit the induction and function of human LAK cells.

We have examined some of the factors which may regulate the generation and function of human lymphokine-activated killer (LAK) cells. In particular we have studied the effect of cytokines other than interleukin-2 on the ability of human LAK cells to kill human tumour cells. By exposing human tumour cells to human LAK-cells in the presence and absence of interleukin-3 or interleukin-4, we were able to demonstrate that each of these cytokines was able to severely reduce the amount of tumour cell killing. Additionally, we examined the effect of interleukin-3 or interleukin-4 on the production in vitro of human LAK cells by including these materials with interleukin-2 while LAK-cells were being induced. These results showed that not only were these cytokines able to inhibit human LAK-cell function, but they were also able to strongly reduce the ability of interleukin-2 to generate human LAK-cells.

Animals↗