Cetuximab ± chemotherapy enhances dendritic cell-mediated phagocytosis of colon cancer cells and ignites a highly efficient colon cancer antigen-specific cytotoxic T-cell response in vitro.

Cetuximab is a human/mouse chimeric IgG1 monoclonal antibody (mAb) to epidermal growth factor receptor, approved for colorectal carcinoma treatment in combination with chemotherapy. The immune-mediated effects elicited by its human fraction of crystallization moiety might critically contribute to the overall anti-tumor effectiveness of the antibody. We therefore investigated cetuximab ability to promote colon cancer cell opsonization and phagocytosis by human dendritic cells (DCs) that are subsequently engaged in antigen-cross presentation to cytotoxic T-lymphocyte (CTL) precursors. Human colon cancer cell lines were evaluated for susceptibility to DC-mediated phagocytosis before and after treatment with chemotherapy ± cetuximab in vitro. Human DCs loaded with control or drug-treated cetuximab-coated colon cancer cells were used to in vitro generate cytotoxic T cell clones from peripheral blood mononuclear cells of human leucocyte antigen-A(*)02.01(+) donors. T-cell cultures were characterized for immune-phenotype and tumor-antigen specific CTL activity. The results confirmed that treatment of tumor cells with irinotecan + L-folinate + 5-flurouracil (ILF) or with gemcitabine + ILF increased tumor antigen expression. Moreover, malignant cells exposed to chemotherapy and cetuximab were highly susceptible to phagocytosis by human DCs and were able to promote their activation. The consequent DC-mediated cross-priming of antigens derived from mAb-covered/drug-treated cancer cells elicited a robust CTL anti-tumor response. On the basis of our data, we suggest a possible involvement of CTL-dependent immunity in cetuximab anti-cancer effects.

O6-(4-bromothenyl)guanine (PaTrin-2), a novel inhibitor of O6-alkylguanine DNA alkyl-transferase, increases the inhibitory activity of temozolomide against human acute leukaemia cells in vitro.

Anti-tumour activity of triazene compounds of clinical interest [i.e. dacarbazine and temozolomide (TMZ)] relies mainly on the generation of methyl adducts to purine bases of DNA. Two DNA repair enzyme systems, i.e. the O6-guanine-alkyl-transferase (MGMT) and mismatch repair (MMR), play a predominant role in conditioning the cytotoxic effects of triazenes. In particular, high levels of MGMT associated with target cells are responsible of resistance to triazenes. On the contrary, the presence of MMR is required for the cytotoxic effects of these compounds. Previous studies performed by our group and a more recent clinical investigation reported by Karen Seiter, pointed out that triazene compounds could play an important role in the treatment of refractory acute leukaemia. Leukaemia blasts, especially of lymphoblastic leukaemia, show frequently high levels of MGMT activity. Therefore, it reasonable to hypothesize that combined treatment of leukaemia patients with triazene compounds along with MGMT inhibitors could lead to a better control of the disease. PaTrin-2 (O6-(4-bromothenyl)guanine, PAT) is a potent and scarcely toxic MGMT inhibitor recently introduced in clinical trials. This drug is used in combination with triazene compounds in order to augment their anti-tumour efficacy against neoplastic cells endowed with high MGMT activity. The present report describes, for the first time, pre-clinical in vitro studies on the cytotoxic activity of combined treatment with PAT+TMZ against long-term cultured leukaemia cells and primary leukaemia blasts obtained from patients with acute lymphoblastic leukaemia or acute myeloblastic leukaemia. The results point out that, both in long-term cultured leukaemia cell lines and in primary blast samples, PAT could improve dramatically the sensitivity of malignant cells to the cytotoxic effects of TMZ. This sensitizing effect is detectable when leukaemia cells show resistance mechanisms based on a MGMT-proficient phenotype. On the contrary, when resistance to TMZ is dependent on MMR deficiency, no influence of PAT can be detected in various experimental conditions. In conclusion, these results appear to provide disease-oriented rational basis to design novel clinical protocols for the treatment of acute leukaemia with combined administration of PAT and triazene compounds.

Focus on Fotemustine.

Fotemustine is a cytotoxic alkylating agent, belonging to the group of nitrosourea family. Its mechanism of action is similar to that of other nitrosoureas, characterized by a mono-functional/bi-functional alkylating activity. Worth of consideration is the finding that the presence of high levels of the DNA repair enzyme O6-methylguanine-DNA-methyltransferase (MGMT) in cancer cells confers drug resistance. In different clinical trials Fotemustine showed a remarkable antitumor activity as single agent, and in association with other antineoplastic compounds or treatment modalities. Moreover, its toxicity is generally considered acceptable. The drug has been employed in the treatment of metastatic melanoma, and, on the basis of its pharmacokinetic properties, in brain tumors, either primitive or metastatic. Moreover, Fotemustine shows pharmacodynamic properties similar to those of mono-functional alkylating compounds (e.g. DNA methylating drugs, such as Temozolomide), that have been recently considered for the management of acute refractory leukaemia. Therefore, it is reasonable to assume that this agent could be a good candidate to play a potential role in haematological malignancies.

Transient increase of plasma ghrelin after laparoscopic adjustable gastric banding in morbid obesity.

Ghrelin is a peptide hormone with orexigenic properties that is produced by the stomach. Ghrelin and leptin are thought to be the main regulators of appetite and body weight. The present study was aimed at evaluating the effect of weight reduction after laparoscopic adjustable gastric banding (LAGB) on metabolic parameters and energy balance regulatory peptides. Patients were evaluated before and 6, 12, 24 or 36 months after the procedure, and a blood sample was obtained. Ghrelin rose 6 and 12 months after LABG, and then returned to near-baseline levels. In our study, the correlation between ghrelin and BMI was weak, but a strong significant correlation was maintained between leptin and BMI. We conclude that ghrelin is mainly stimulated by the negative caloric balance, and hypothesize that ghrelin is involved in maintaining a stable body weight, while leptin signals the body energy store; both hormones together are part of a more complex feedback mechanism.

Adjuvant therapy of melanoma patients (stage II, III): a pilot immuno-toxicological study.

A pilot study was conducted to assess the tolerability and the effect on host immunity of a post-surgery adjuvant treatment of melanoma patients with an anti-angiogenic agent, Tamoxifen (TAM, 20 mg/die p.o., daily), combined with immunomodulating cytokines, i.e. recombinant interleukin-2 (IL-2, 4 MUI/m2 s.c., day 8,10,12) and alpha-2b-interferon (IFN, 3 MUI/m2 i.m., day 15,17,19), starting a new cycle on day 21, for a total of 12 cycles. Fifty patients (pts) entered into the study, 27 males and 23 females with a median age of 55 years (range 25-75), performance status (ECOG) 0 with melanoma stage IIA (12 patients), stage IIB (28 patients), stage III (10 patients). Preliminary in vitro studies showed that TAM does not interfere with up-regulation of natural immunity induced by IFN, IL-2, or IFN + IL-2 in normal peripheral blood mononuclear cells (MNC). The clinical study indicates that the protocol was well tolerated. Increase of NK and LAK activity of patient MNC was observed on day 15. The mean disease-free interval was 10 months and 40 pts were alive at 5 years of follow-up. Further investigations should be performed to test effectiveness of this protocol in a randomized study.

DNA repair enzymes and cytotoxic effects of temozolomide: comparative studies between tumor cells and normal cells of the immune system.

O6-alkylguanine-DNA alkyltransferase (OGAT) and the mismatch repair system (MRS) play a crucial role in the susceptibility of tumor cells to the cytotoxic effects of agents that generate O6-methylguanine in DNA, including the triazene compound temozolomide (TMZ). Studies performed with peripheral blood mononuclear cells (MNC) showed that TMZ was scarcely active on lymphocyte functions not dependent on cell proliferation (e.g. NK activity and cytokine-mediated induction of CD1b molecule in adherent MNC). In contrast, TMZ depressed proliferation and lymphokine activated killer (LAK) cell generation in response to IL-2. In this case, a reasonably good inverse relationship was found between OGAT levels of MNC and their susceptibility to TMZ. This study also analyzed the ratio of the toxic effect of TMZ on MNC and on tumor cells (i.e. "Tumor-Immune Function Toxicity Index", TIFTI). A particularly favorable TIFTI can be obtained when OGAT levels are extremely high in MNC and markedly low in tumor cells. This holds true for MRS-proficient neoplastic cells, but not for MRS-deficient tumors. In conclusion, strategies aimed at modulating OGAT and MRS may improve the clinical response to TMZ. However, the use of OGAT inhibitors to potentiate the antitumor activity of TMZ might result in a concomitant increase of the immunosuppressive effects of the drug, thus reducing the relative TIFTI.

3-month formulation of goserelin acetate ('Zoladex' 10.8-mg depot) in advanced prostate cancer: results from an Italian, open, multicenter trial.

OBJECTIVES: To determine the endocrine effects, efficacy and tolerability of the 3-month formulation of goserelin acetate ('Zoladex' 10.8-mg depot; 'Zoladex' is a trade mark of the AstraZeneca group of companies) in the treatment of patients with advanced prostate cancer. METHODS: Between February 1996 and October 1997, this open, multicentre study enrolled 120 patients with locally advanced (T3/4) or metastatic (N+ or M1) disease, or an increase in prostate-specific antigen (PSA) level after radical prostatectomy. Patients received goserelin acetate 10.8-mg depot every 12 weeks until clinical progression or interruption for adverse events or other reasons. RESULTS: The mean testosterone concentrations were suppressed to the castration range (< or =2 nmol/l) after 4 weeks of treatment and remained suppressed throughout the study. In total, 99/115 (86%) patients had a serum PSA response, and the mean PSA value decreased significantly during treatment (p = 0.006). The mean PSA level at baseline was significantly lower in patients without disease progression compared to those who experienced disease progression (p = 0.0002). Goserelin acetate 10.8-mg depot was well tolerated and there were no injection site reactions. CONCLUSIONS: The goserelin acetate 10.8-mg depot is well tolerated with no injection site reactions. It produces PSA responses and provides reliable suppression of serum testosterone.

In vitro generation of cytotoxic T lymphocytes against HLA-A2.1-restricted peptides derived from human thymidylate synthase.

5-Fluorouracil (5-FU) is a pyrimidine antimetabolite active against colorectal carcinoma and other malignancies of the digestive tract. Over-expression or mutation of thymidylate synthase (TS), the target enzyme of the 5-FU metabolite, 5-fluorodeoxyuridine monophosphate, is strictly correlated with cancer cell resistance to 5-FU. On this basis we investigated whether TS is a potential target for active specific immunotherapy of human colon carcinoma, which acquires resistance to 5-FU. Three TS-derived epitope peptides which fit defined amino acid consensus motifs for HLA-A2.1 binding were synthesized and investigated for their ability to induce human TS-specific cytotoxic T cell (CTL) responses in vitro. CTL lines specific for each peptide were established by stimulating peripheral blood mononuclear cells (PBMC) from an HLA-A2.1+ healthy donor with autologous dendritic cells loaded with TS peptide. Specific CTL lines showed HLA-A2.1-restricted cytotoxicity in vitro to HLA-A2.1+ target cells pulsed with the specific TS peptide and to HLA-class I matching colon carcinoma target cells over-expressing TS enzyme after exposure to 5-FU. Recognition by CTL lines suggests that these TS peptides may be potential candidates for use in a peptide-based vaccine against 5-FU resistant colon carcinoma.

Cytotoxic and clastogenic effects of a DNA minor groove binding methyl sulfonate ester in mismatch repair deficient leukemic cells.

Mismatch repair deficiency contributes to tumor cell resistance to O6-guanine methylating compounds and to other antineoplastic agents. Here we demonstrate that MeOSO2(CH2)2-lexitropsin (Me-Lex), a DNA minor groove alkylating compound which generates mainly N3-methyladenine, has cytotoxic and clastogenic effects in mismatch repair-deficient leukemic cells. Moreover, MT-1 cells, which express p53 upon drug treatment and possess low levels of 3-methylpurine DNA glycosylase activity, are more susceptible to cytotoxicity induced by Me-Lex, with respect to p53-null and 3-methylpurine DNA glycosylase-proficient Jurkat cells. In both cell lines, the poly(ADP-ribose) polymerase inhibitor 3-aminobenzamide, which inhibits base excision repair capable of removing N-methylpurines, increases cytotoxicity and clastogenicity induced by Me-Lex or by temozolomide, which generates low levels of N3-methyl adducts. The enhancing effect is more evident at low Me-Lex concentrations, which induce a level of DNA damage that presumably does not saturate the repair ability of the cells. Nuclear fragmentation induced by Me-Lex + 3-aminobenzamide occurs earlier than in cells treated with the single agent. Treatment with Me-Lex and 3-aminobenzamide results in augmented expression of p53 protein and of the X-ray repair cross-complementing 1 transcript (a component of base excision repair). These results indicate that N3-methyladenine inducing agents, alone or combined with poly(ADP-ribose) polymerase inhibitors, could open up novel chemotherapeutic strategies to overcome drug resistance in mismatch repair-deficient leukemic cells.

Drug-induced modulation of carcinoembryonic antigen (CEA) expression in neoplastic cells from a patient with rectal cancer.

Treatment with 5-fluorouracil (5-FU) or recombinant interferon-gamma (IFN), alone or in combination, was found to increase carcinoembryonic antigen (CEA) expression in several carcinoma cell lines. In this study we examined the in vitro effect of these agents on CEA expression of tumor cells, obtained from a patient operated for rectal cancer. The results showed that exposure of cancer cells to 5-FU or to IFN resulted in increased CEA levels in terms of percentage of CEA-positive cells and mean fluorescence values, as indicated by FACS analysis. However, drug combination did not induce CEA expression higher than that provided by single agents alone. Treatment with 5-FU or with IFN produced a reduction of the total number of viable cells. Moreover, Western blot analysis revealed that exposure of cancer cells to each drug was followed by a substantial increase of the total cellular CEA content. On the contrary, 5-FU in combination with IFN did not increase the expression of the antigen more than that obtained by single agents. Noteworthy, exposure of CEA-negative cells from adjacent normal rectal tissue to both agents alone or in combination, did not result in CEA induction. In conclusion, the present results suggest new approaches aimed at (a) increasing the sensitivity of diagnostic procedures based on detection of CEA-positive tumor cells; (b) facilitating the recognition of CEA-positive cancer cells by immune responses induced by anti-CEA peptide vaccines.

Suppression of telomerase activity as an indicator of drug-induced cytotoxicity against cancer cells: in vitro studies with fresh human tumor samples.

Telomerase is a ribonucleoprotein complex with reverse-transcriptase activity responsible for telomere reconstitution. High telomerase activity was found in cancer cells, but not in differentiated homologous nonmalignant tissues. We demonstrated previously that the disappearance of telomerase activity is a reliable marker of tumor cell killing in human cancer cell lines. We have investigated the possibility of evaluating chemosensitivity of neoplastic cells of different origin [ovary, lung, breast, gastrointestinal, skin (melanoma)] obtained from cancer patients, by measuring residual telomerase activity after drug treatment in vitro. Using the classical telomeric repeat amplification protocol ("TRAP") assay based on polymerase chain reaction, we examined telomerase activity of untreated or drug-treated tumor cell suspensions, derived from the processing of surgical specimens. Feasibility and reproducibility of the assay were evaluated according to various parameters, including drug concentration, time of in vitro culture, and type of tumor. The results indicated that the assay is highly sensitive and reproducible, and can be performed using surgical specimens in a reasonable percentage of cases, ranging from 40% (breast cancer) to 100% (ovarian cancer). Moreover, the assay provides comparable results using a wide range of tumor cells, and the presence of normal cells does not interfere with the results. Prolonged tumor cell culture is not required because the assay can be completed within 24 to 72 hours after sample collection. In conclusion, the present investigation provides the technical bases for future studies to evaluate whether this assay would be able to predict patient's response to antitumor agents.

Treatment with temozolomide and poly(ADP-ribose) polymerase inhibitors induces early apoptosis and increases base excision repair gene transcripts in leukemic cells resistant to triazene compounds.

Methylating triazenes have shown marked antileukemic effects, possibly through generation of a variety of DNA adducts. Cells tolerant to O6-methylguanine due to a defect in the mismatch repair system (MRS), might become sensitive to other methyl adducts, by inhibiting the N-methylpurine repair, which requires base excision repair (BER) and poly(ADP-ribose) polymerase (PADPRP). Therefore, MRS-deficient Jurkat leukemic cells resistant to methylating triazenes, have been treated with temozolomide (TZM) and PADPRP inhibitors. Expression of PADPRP or molecules involved in the BER system [3-methylpurine-DNA glycosylase (MPG) and X-ray repair cross-complementing 1 (XRCC1)], have been explored. Cytotoxic effects of TZM associated with PADPRP inhibitors are evident shortly after treatment, suggesting that completion of cell division is not required for the lethal effect of the drug combination. Increase of PADPRP or MPG transcripts was found after treatment with TZM alone or combined with PADPRP inhibitor. XRCC1 transcript was positively modulated only in the case of drug combination. This could suggest that in the presence of PADPRP inhibitor, persistence of DNA damage triggers XRCC1 transcription. Our results suggest that association of TZM and PADPRP inhibitors might be of benefit for MRS-deficient malignancies unresponsive to the methylating agent.

Adjuvant treatment of breast cancer: a pilot immunochemotherapy study with CMF, interleukin-2 and interferon alpha.

Immune responses, including natural immunity (NI), potentiate the antitumor effects of chemotherapy. Since interferons and interleukin-2 (IL-2) augment NI, a pilot study was conducted to assess the tolerability and the effects on host immunity of adjuvant chemotherapy associated with IL-2 + interferon alpha (IFN) in breast cancer patients after surgery. Ten patients underwent alternating 28-day cycles of chemoimmunotherapy [cyclophosphamide + methotrexate + 5-fluorouracil (CMF, days 1, 8) + IL-2 (days 15 19) + IFN (day 22)] and chemotherapy alone (CMF). With this regimen each patient was considered to be a reasonable "control" of herself. Blood cell count and natural killer cell activity (NKA) were tested on days 1, 8, 15, 22, and 23. Preliminary in vitro studies indicated that IL-2 or IFN antagonized the severe inhibition of NKA induced by hydroxy-peroxy-cyclophosphamide (in vitro active derivative of cyclophosphamide), alone or associated with methotrexate + 5-fluorouracil. Nine patients completed all six alternating cycles, whereas one patient proved to have metastatic lesions after four cycles. The protocol was well tolerated, although leukopenia (CMF alone) and leukopenia with fever and moderate or minimal flu-like symptoms (CMF + IL-2 + IFN) were generally observed. Treatment with IL-2 facilitated complete recovery of white cell counts and NKA after the nadir on day 15. In conclusion, the present protocol appears to be well tolerated and amenable to administration on an outpatient basis. Therefore, further investigations should be performed to verify whether CMF + IL-2 + IFN would be superior to CMF alone for adjuvant treatment after surgery in breast cancer.

Sensitivity of human melanoma cells to oestrogens, tamoxifen and quercetin: is there any relationship with type I and II oestrogen binding site expression?

We investigated the effect of oestrogens, anti-oestrogens and flavonoids on the growth of a human melanoma cell line (SK-Mel-28) and, at the same time, the presence of both type I oestrogen receptors (ERs) and type II oestrogen binding sites (type II EBS) to gain a fuller picture of the relationship between melanoma cell proliferation and receptor status. 17beta-Oestradiol (E2) and the flavonoid quercetin (Q) produced a marked inhibition of proliferation, but only at the highest dose used (10(-5) M) and only when added daily to the medium. Diethylstilboestrol (DES) (10(-5) M) was effective in inhibiting cell growth when the medium was renewed every 3 days and produced a more pronounced reduction when added daily to the medium. Tamoxifen (TAM) inhibited cell proliferation at a dose starting from 10(-7) M when the medium was renewed every 3 days. When added daily to the medium, it did not induce a greater inhibitory effect and it was cytotoxic at 5 x 10(-6) M and 10(-5) M. The antiproliferative effect of E2, DES and Q did not seem to be dependent on their interaction with ERs, which were minimally detected in SK-Mel-28 in both immunocytochemical and biochemical assays. Our model revealed, through a biochemical assay, a large number of type II EBSs which could be involved in the anti-oestrogen action, but this does not exclude the involvement of other mechanisms. Finally, TAM (10(-5) M) appeared to reduce the activity of the DNA repair enzyme O6-alkylguanine-DNA alkyltransferase, an effect that could be interesting from the point of view of the therapeutic efficacy of alkylating agents.

Effect of the combined treatment with 5-fluorouracil, gamma-interferon or folinic acid on carcinoembryonic antigen expression in colon cancer cells.

5-Fluorouracil (5-FU) and human recombinant gamma-interferon (gamma-IFN) were found to increase the expression of carcinoembryonic antigen (CEA) in human cancer cells in vitro. In the present study, the antimetabolite was associated with gamma-IFN or folinic acid (FA), a biochemical modulator of cellular metabolism of 5-FU, able to increase its antineoplastic activity. Treatment of two human colon cancer cell lines (HT-29 and WiDr) with 5-FU + gamma-IFN resulted in an increase of CEA expression higher than that obtainable with both agents alone, although no synergistic effects were obtained. This was demonstrated in terms of: (a) mRNA transcripts (HT-29); (b) cytoplasm and membrane CEA protein levels detected by Western blot analysis (HT-29); and (c) plasma membrane reactivity determined by flow cytometry analysis (HT-29 and WiDr). Moreover, 5-FU + gamma-IFN increased HLA class I molecules in the HT-29 cell membrane over that obtainable with gamma-IFN alone. In contrast, both agents did not induce the expression of the costimulatory molecule B7-1. Treatment with FA enhanced the antitumor effect of 5-FU but not its ability to augment CEA expression. This suggests that the FA-sensitive biochemical mechanism of action of 5-FU is not involved in its effect on CEA expression. In vivo studies showed, for the first time, that 5-FU, alone or combined with gamma-IFN, increases the amount of CEA protein over controls, either in cancer cells or in peripheral blood of nude mice bearing HT-29 cells. These results could be of potential diagnostic and/or therapeutic value when CEA protein is the target of humoral or cell-mediated immunity.

Decline in telomerase activity as a measure of tumor cell killing by antineoplastic agents in vitro.

Telomerase activity is frequently associated with the malignant phenotype, and it can be considered an almost ubiquitous tumor marker. In this study, we evaluated telomerase activity in telomerase-positive human tumor cell lines exposed in vitro to antineoplastic agents. The results show that drug-induced cell killing of tumor cells is associated with a decline in detectable telomerase activity. The decrease of telomerase activity levels paralleled cell growth impairment evaluated by cell count or by measurement of cell ability to convert tetrazolium salt to colored formazan [3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide assay]. The observed telomerase activity remaining after treatment with antineoplastic agents is most likely to reflect activity from the remaining viable cells. When tumor cell lines resistant to the chemotherapeutic agents temozolomide or doxorubicin were treated with these compounds, no decline of telomerase activity or cell growth was observed. The results of the present study indicate that resistance of neoplastic cells to chemotherapeutic agents can be monitored by following telomerase activity. Moreover, the test can be performed with a limited number of neoplastic cells, such as those frequently obtained from tumor biopsies. These findings provide a rationale for developing new in vitro chemosensitivity assays, and detection of telomerase activity may be a novel marker of chemotherapy failure.

Development of a novel in vitro chemosensitivity assay: telomerase as a possible marker of tumor cell survival.

Telomerase is a ribonucleoprotein enzyme which is involved in the maintenance of chromosome ends. Telomerase activity (TLMA) is required for cell immortality and can be considered a ubiquitous tumor marker. In this study we describe a new approach for developing in vitro chemosensitivity assays based on the assessment of TLMA in tumors, upon treatment with antineoplastic agents. The results of preliminary studies on in vitro cultured tumor cell lines indicate that TLMA inhibition can be used as a marker of tumor cell killing by anticancer drugs. Therefore the present investigation provides the rational basis for an in vitro chemosensitivity assay based on TLMA evaluation.

In vitro combined effects of a triazene compound and interferon-beta on natural immunity against lymphoblastoid cells: studies at effector and target cell level.

It was shown that Dacarbazine and other triazene compounds render murine leukemias highly immunogenic and susceptible to natural immunity (NI). In addition a pilot clinical study revealed that Dacarbazine can be cytotoxic for bone marrow blasts in patients with acute non-lymphoblastic leukemias through a mechanism that could be, at least in part, of immunological origin. However triazenes depress antigen-dependent responses and NI, whereas interferons, including interferon-beta (IFN), antagonize drug-induced impairment of NI. Therefore the complex interaction between triazenes and IFN on NI effector (i.e. NK) lymphocytes and human target lymphoblastoid cells has been investigated. The results show that: (a) IFN increases NK activity and antagonizes the depressive effects of methyl-triazene-benzoic acid (MTBA, an in vitro active triazene compound) on the NK function; (b) a lymphoblastoid cell line exposed to multiple in vitro treatments with MTBA, shows increased growth rate, augmented chemoresistance to MTBA, and higher susceptibility to NI than parental cells; (c) as expected IFN pretreatment down-regulates the susceptibility of lymphoblastoid cells to NK effectors; (d) however a net "therapeutic gain" was found if the overall influence of MTBA+IFN on target and effector cells is considered.

Drug-mediated changes in the susceptibility of human lymphoblastoid B cells to NK-mediated cytolysis: studies with a triazene compound.

Previous studies have shown that treatment of leukemia-bearing mice with triazene compounds results in a profound alteration of the immunological properties of leukemic cells. These cells become highly immunogenic and susceptible to natural immunity (NI). Moreover, in a pilot clinical study, dacarbazine was found to suppress bone marrow blasts in patients with acute non-lymphoblastic leukemias. The cytotoxic mechanism involved could be of biochemical and immunological origin as well. Therefore experiments were carried out to test whether triazenes could influence the susceptibility of blast cells to human NI effector lymphocytes (represented, at least in part, by NK cells). The results obtained with target Epstein-Barr virus (EBV)-immortalized B cells and effector cells of different donors, showed that: (a) multiple in vitro treatments of lymphoblastoid cells with methyl-triazene-benzoic acid (MTBA, a triazene compound active in vitro), gave origin to lines that were more resistant than the parental lines to the antitumor effects of MTBA; (b) MTBA-treated lines were more susceptible (37.5% of cases), or less susceptible (31.2% of cases) to NI than parental cells. Effector lymphocytes of various donors recognized different changes in susceptibility to natural killer (NK)-mediated lysis; (c) treatment of parental or MTBA-treated lines with interferon-beta reduced target cell susceptibility to NK-mediated cytolysis, but increased NK activity and lymphoblast chemosensitivity to MTBA.

Immuno-chemotherapy of advanced colorectal cancer with alpha-2a interferon and 5-fluorouracil. Immunopharmacological studies.

Twelve patients with metastatic colorectal cancer received alternating cycles of low immunomodulating doses of alpha-IFN + 5-Fluorouracil (5-FU) or 5-FU alone. Hematological, biochemical and physical evaluation showed that both treatment cycles were well tolerated. However, transient fever and moderate flu-like symptoms were observed following alpha-IFN administration. Treatment with 5-FU alone produced long-lasting inhibition of CD8+ T lymphocytes, but did not depress NK activity (NKA). Combined treatment with alpha-IFN produced a short-term increase of NKA and antagonized the effect of 5-FU on CD8+ cells on day 5 of the cycle. Parallel studies on in vitro models showed antiproliferative effects of 5-FU on PHA-stimulated MNC and confirmed the preferential inhibition of CD8+ cells. Pretreatment with alpha-IFN did not reverse the effect of 5-FU on CD8+ lymphocytes, but partially protected MNC from the toxic effects of the drug. This was presumably due to the cytostatic effects induced by alpha-IFN on MNC before exposure to the cycle-specific antineoplastic agent. This investigation suggests that alpha-IFN could play a positive role in immuno-chemotherapy of colorectal cancer through multiple mechanisms not entirely related to direct antitumor effects of the agent.