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

Preclinical antitumor activity of ethyldeshydroxysparsomycin in combination with cisplatin

The efficacy of cisplatin (CDDP) in combination with the protein synthesis inhibitor ethyldeshydroxysparsomycin (EDSM) has been tested in two tumor models at various schedules. Mice with L1210 leukemia or B16 melanoma were treated with CDDP alone or in combination with EDSM. Against L1210 leukemia, which is sensitive to CDDP, combinations elicited increases in life-span for all treatment schedules compared to those achieved with the corresponding dose of CDDP. Moreover, the combination of EDSM with this platinum compound yielded a cure rate > 80%, compared to < 35% for single CDDP treatment. Although the B16 melanoma is rather resistant to both CDDP and EDSM, combinations of these agents against B16 melanoma showed schedule dependent efficacy and in certain schedules significant therapeutic advantage over individual drug treatment, but cures were not observed. Our results suggest that EDSM has significant synergistic capabilities in both animal tumor models, but strong therapeutic enhancement of cisplatin efficacy is only seen when the tumor is sensitive to CDDP.

N-methylformamide as a potential therapeutic approach in colon cancer

PURPOSE

The effect of N-methylformamide, used in combination with the antineoplastic drugs adriamycin and cisplatin, on the cell survival of a colon carcinoma cell line (HT-29) was investigated. To better understand the mechanism involved in N-methylformamide-mediated chemosensitization, we evaluated the N-methylformamide effect on cell volume and surface expression of some integrins molecules (VLA2, VLA5, and VLA6) of the HT-29 cell line.

METHODS

The cell survival was evaluated by clonogenic assay; integrins surface expression was analyzed by means of flow cytometry; cell volumes were determined using a Coulter Channalyzer.

RESULTS

A Noncytotoxic dose of N-methylformamide (170 mM) sensitizes the HT-29 cell line to the lethal activity of both adriamycin and cisplatin. The analysis of cell volume showed that N-methylformamide exposure induces an increase in cell volume. Flow cytometric analysis of VLA2, VLA5, and VLA6 receptors showed that N-methylformamide increases the expression of the three integrins by 30 to 40 percent.

CONCLUSION

The plasma membrane could constitute one of the N-methylformamide targets and might be involved in the differentiation and chemosensitizing effects caused by this agent. Moreover, N-methylformamide could improve colon cancer treatment when used in combination with antineoplastic drugs.

Combination therapy with cisplatin: modulation of activity and tumour sensitivity

Although cisplatin is applied with success in clinical oncology, this success is limited because some cancers are initially unresponsive to cisplatin or become so during treatment. In this review, some strategies to overcome this problem are discussed. Among these are combination with the differentiation inducing agent, retinoic acid, combination with radiotherapy, and the use of hyperthermia.

Cytoskeleton-dependent surface blebbing induced by the polar solvent N-methylformamide

In vivo and in vitro studies performed on the polar solvent N-methylformamide (NMF), as well as on its association with chemotherapeutic agents or X rays, have clearly demonstrated that this compound is capable of inducing changes in biological characteristics of tumor cells, e.g., cell differentiation. However, the mechanism of action of NMF is far from being elucidated. Hence, in order to better clarify such a mechanism an in vitro study was carried out by using mouse fibroblasts in primary culture (MEF) and human melanoma cultured cells (M14). Results obtained by immunocytochemical and ultrastructural methods with doses of NMF ranging from 0.1 to 7% are reported here. As a general rule, a different sensitivity (in terms of cytopathologic changes induced by NMF) was found between the cell types considered. In fact, melanoma cells appeared to be highly susceptible to the action of the drug, undergoing severe morphological modifications represented mainly by a reversible dose and time-dependent cell rounding and surface blebbing. In contrast, NMF-induced injury in MEF cells was characterized mainly by a simple retraction of the cell body. A cytochemical analysis of the expression of certain membrane antigens (e.g., glycoproteins, epidermal growth factor receptor, B2 microglobulin) in NMF-treated M14 cells undergoing blebbing was also carried out. A randomly distributed labeling of such molecules was observed. Accordingly, freeze-fracturing electron microscopic analysis also displayed a random distribution of intramembrane particles over the plasma membrane. When subcellular changes induced by the drug were investigated, a remarkable modification of cytoskeletal components was detected in both cell types. In particular, cross-linked actin microfilament bundles were easily observed in NMF-exposed MEF cells. Finally, when different experimental conditions which perturb calcium ion homeostasis or restore protein thiol group reduced state were analyzed, a noticeable impairment of the blebbing phenomenon was observed. Thus, a target effect of NMF on the microfilament system, probably leading, in turn, to several subcellular changes and cell surface blebbing, can be hypothesized. Such a cytoskeletal element-dependent cytopathology appears to be related to changes of the oxidized state of such molecules as well as to calcium ion perturbations.

N-methylformamide effects on cell proliferation and antigenic pattern in HT-29 colon carcinoma cell line

The effects of the differentiating agent N-methylformamide (NMF) on cell proliferation and antigenic pattern of HT-29 colon carcinoma cells have been investigated. The cell line was cultured in the presence, or absence, of 1% NMF and tested for the above mentioned characteristics, both in vitro and after injection into nude mice. The percentage of cells in the various cell cycle compartments was estimated by flow cytometry. The presentation on the cell surface of molecules such as tumour associated antigens (TAAs), HLA class I molecules and epidermal growth factor receptor (EGF-R) was analysed by ELISA, flow cytometry and immunohistochemistry. Results demonstrate that NMF impairs HT-29 cell proliferation with a remarkable accumulation in the G0/G1 phases, as well as inducing a modification of the membrane antigenic pattern. The presence of NMF in the culture medium decreases the TAAs and EGF-R whereas HLA antigen maintains the same level of positivity in the two cell lines. These alterations are consistent with a different behaviour in vivo of the tumours originated from NMF treated and untreated cells. Tumours derived from NMF treated cells show a delay in the appearance and low levels of immunodetectable carcinoembryonic antigen (CEA) molecules.

Different effects of sequential combinations of N-methylformamide with 5-fluorouracil on human colon carcinoma cells growing in nude mice

The effects of the combination of N-methylformamide (NMF) with 5-fluorouracil (5-FU) on tumor growth and morphological features of human colon carcinoma cells (HT29) implanted in nude mice were assessed. Both agents were administered i.p. at tolerable doses: 5-FU at 19 mg/kg for 5 days and NMF at 200 mg/kg for 12 days. Four main schedules were tested: 5-FU alone, NMF alone, NMF followed by 5-FU and 5-FU followed by NMF. The last sequence was the most effective, as compared with the other treatment regimens. In particular, the 5-FU----NMF combination induced a tumor inhibition of about 75% at the end of the treatments (17th day) versus an inhibition of 23%-43% in the other schedules. Morphological observations, carried out by light and electron microscopy, indicated a possible relationship between the presence of structural changes and tumor growth inhibition. The results of this study renew interest in the use of NMF in sequential combination confirming sequence as a critical factor for the optimal combination of NMF and 5-FU.

Importance of cell cycle perturbations on the effectiveness of N-methylformamide and anti-neoplastic drugs in combination

The effect of N-methylformamide (NMF) in combination with Adriamycin (ADM) and cis-diamminedichloroplatinum (DDP) on the cell survival and cell cycle kinetics of two human tumour lines was assessed: HT29 colon carcinoma and M14 melanoma cells were exposed to ADM and DDP alone or in combination with a non-cytotoxic dose of NMF, according to different schedules. The results demonstrate that NMF exposure sensitized both tumour cell lines to the lethal activity of ADM and DDP; however, reverse sequences had to be applied to reach an increase in the lethal activity of the two different drugs. The ADM-NMF combination determined a powerful decrease in the surviving fraction of the two cell lines when ADM was given as the first agent (ADM----NMF), while the reverse sequence did not increase the ADM cytotoxic effect. With respect to the DDP-NMF association, the sequence which accounted for a greater sensitizing effect was NMF administration followed by DDP treatment (NMF----DDP). This work demonstrates the importance of timing in combined treatments which involve NMF. A delay in cell proliferation elicited by NMF exposure could be responsible for the effectiveness of the combined treatment.

N-methylformamide affects spontaneous metastases of 3LL lines and increases natural killer activity of tumor-bearing mice

The antitumor activity of the polar solvent N-methylformamide (NMF) was evaluated on three lines derived from the Lewis lung carcinoma (3LL), endowed with different metastatic potential. Two administration schedules were tested, these being repeated regimens of NMF (200 mg/kg per dose) for 12 consecutive days, starting 24 h or 6-10 days after tumor implantation (early or late treatment, respectively). The results of the present work can be summarized as follows: (1) NMF regimens did not greatly affect tumor growth behavior of 3LL lines; conversely, they markedly influenced their spontaneous colonizing ability in the lungs, either by delaying early metastatic spread or by reducing the number and size of pulmonary metastases already implanted. (2) A significant increase of NK cell activity during and after early treatment with NMF was observed in the more-metastasizing lines, thus suggesting the possibility of an immunomodulating effect of NMF.

Antitumor and antimetastatic activity of the differentiating agent N-methylformamide in murine tumor systems

N-Methylformamide (NMF), a cell-differentiating agent, was assessed for its antitumor activity against a fibrosarcoma (FSA), a hepatocarcinoma (HCA-I) and a mammary carcinoma (MCA-K), syngeneic to C3Hf/Kam mice. Tumors were grown as solitary tumors in the leg or as artificial or spontaneous micrometastases in the lung. NMF, at a dose of 300 mg/kg, was administered i.p. daily for 6 to 18 days. NMF slowed the growth of FSA and HCA-I tumors and totally inhibited the growth of the MCA-K tumor. However, the effect was transient; tumors resumed their pretreatment growth rate upon cessation of the treatment. Histologically, MCA-K tumors treated with NMF (300 mg/kg daily for six days) underwent considerable cell depopulation and reduction in mitotic activity. The number of artificial metastases, as well as the incidence and the number of spontaneous metastases, were markedly reduced by NMF. This resulted in a prolongation of the survival of mice that had artificial metastases of MCA-K tumor. The in vitro clonogenicity of MCA-K, but not of FSA or HCA-I cells, was reduced. However, in vivo reduction of MCA-K cell clonogenicity was minimal, if any. Thus, NMF is effective in restricting the growth of both solitary tumors and metastases, but the degree of response is highly dependent on tumor type.

Radiosensitization of primary human tumor cell cultures by N-methylformamide

The effects of the differentiation-inducing agent N-methylformamide (NMF) on the radiation response of ten primary human tumor cell cultures were investigated. Cell survival was determined using an adhesive tumor cell culture system. NMF (1%) was added to cultures on Day 1 and was left for 6 days; cultures were irradiated with graded doses of X rays (1.0-6.0 Gy) on Day 4. Using survival at 2.0 Gy as a comparative endpoint, eight of ten cultures tested exhibited enhanced radiosensitivity upon exposure to NMF. In sensitized cultures, the dose-enhancement factors ranged from 1.3 to 2.5. The NMF-mediated radiosensitization did not appear to be dependent on the histologic cell type. The results presented support previous data obtained from established cell lines and suggest that NMF may offer clinical benefits against a variety of tumor types when used in combination with radiotherapy.

The effects of N-methylformamide on artificial and spontaneous metastases from a murine hepatocarcinoma

The effects of the differentiation-inducing polar solvent N-methylformamide (NMF) on artificially induced and spontaneous metastases from a murine hepatocarcinoma (HCA-1) in C3Hf/Kam mice were investigated. Exposure of HCA-1 cells in vitro for 6 days to 1.0% or 1.25% NMF resulted in an increase in the number of lung nodules formed in mice when these cells were injected into their tail veins. This in vitro NMF exposure increased cell volume and induced only a slight amount of cytotoxicity. Administration of NMF to mice 1 day before i.v. tumour cell inoculation resulted in a dose-dependent increase in the number of lung nodules formed, beginning at an NMF dose of 600 mg kg-1. NMF caused a similar magnitude of metastasis enhancement in immunosuppressed mice. However, when the maximum dose tested (1,800 mg kg-1) was administered as 6 daily fractions of 300 mg kg-1 each, no increase in artificial metastases was detected. Administration of NMF to mice one day after i.v. tumour cell injection resulted in a dose-dependent decrease in the number of lung nodules. In mice bearing 5-6 mm HCA-1 leg tumours, treatment with 6 daily fractions of NMF (300 mg kg-1 each) significantly reduced the number of spontaneous pulmonary metastases, yet had very little effect on the growth of the primary tumour. These data suggest that, in a clinically relevant treatment setting, NMF can reduce metastasis formation.