Dipyridamole enhances an anti-proliferative effect of interferon in various types of human tumor cells

Dipyridamole enhances the anti-cancer ability of aspirin against colorectal cancer by inducing apoptosis in an unfolded protein response-dependent manner

PURPOSE

Available evidence indicates that dipyridamole enhances the anti-thrombotic effects of aspirin for the prevention of secondary strokes. Aspirin is a well-known non-steroid anti-inflammatory drug. This anti-inflammatory property has turned aspirin into a potential drug for inflammation-related cancers such as colorectal cancer (CRC). Here, we aimed to explore whether the anti-cancer effect of aspirin against CRC could be improved by combined administration with dipyridamole.

METHODS

Population-based clinical data analysis was conducted to assess a possible therapeutic effect of combined dipyridamole and aspirin treatment in inhibiting CRC compared with either monotherapy. This therapeutic effect was further verified in different CRC mouse models, i.e. an orthotopic xenograft mouse model, an AOM/DSS mouse model, an Apc^min/+ mouse model and a patient derived xenograft (PDX) mouse model. The in vitro effects of the drugs on CRC cells were tested using CCK8 and flow cytometry assays. RNA-Seq, Western blotting, qRT-PCR and flow cytometry were used to identify the underlying molecular mechanisms.

RESULTS

We found that dipyridamole combined with aspirin had a better inhibitory effect on CRC than either monotherapy alone. The enhanced anti-cancer effect of the combined use of dipyridamole with aspirin was found to rely on the induction of an overwhelmed endoplasmic reticulum (ER) stress and subsequent pro-apoptotic unfolded protein response (UPR), which was different from the anti-platelet effect.

CONCLUSIONS

Our data indicate that the anti-cancer effect of aspirin against CRC may be enhanced by combined administration with dipyridamole. In case further clinical studies confirm our findings, these may be repurposed as adjuvant agents.

Germ line and somatic mutations of BRAF V599E in ovarian carcinoma

It has been shown that ovarian low-grade serous carcinoma evolves out of a stepwise progression from benign serous cystadenoma to serous borderline tumor (SBT) to micropapillary serous carcinoma (MPSC), and that BRAF activation is a very early somatic event in the tumorigenesis. We postulated that BRAF could be a SBT susceptibility gene, and investigated both germ line and somatic mutations of BRAF V599E in 104 ovarian cancer patients. BRAF V599E mutation in histologic samples was found in 5 (24%) of 21 SBTs, 1 (33%) of 3 MPSCs, 1 (17%) of 6 endometrioid carcinomas, but not detected in 42 conventional serous carcinomas, 12 mucinous borderline tumors, 10 mucinous, and 10 clear-cell carcinomas. No V599E mutation could be detected in blood samples from these 104 patients. We also found no BRAF V599E mutation in 101 normal healthy women and 10 well-established ovarian cancer cell lines. Our results suggest that BRAF gene plays a "gatekeeper" role but does not act as a predisposition gene in the development of low-grade serous carcinomas.

Vascular Endothelial Growth Factor-C Expression and Invasive Phenotype in Ovarian Carcinomas

PURPOSE

To investigate the biological correlation between vascular endothelial growth factor (VEGF)-C expression and invasive phenotype in ovarian carcinomas.

EXPERIMENTAL DESIGN

Gene and protein expression levels of VEGF-C in 10 ovarian carcinoma cell lines were correlated with invasive activity of the cells. The correlation between immunohistochemical expression of VEGF-C and tumor aggressiveness in 73 ovarian carcinomas was also examined with respect to clinicopathologic features and patient outcome.

RESULTS

VEGF-C gene and protein expression differed remarkably among the cell lines, and there was a statistical correlation among VEGF-C expression, in vitro invasive activity, and matrix metalloproteinase-2 (MMP-2) gene expression and its activity. Anti-VEGF-C and anti-MMP-2 antibodies inhibited the invasive activity of tumor cells. VEGF-C expression in clinical tissue samples was well correlated with clinical stages, retroperitoneal lymph node metastasis, MMP-2 expression, angiogenesis, lymphangiogenesis, and low apoptotic index (AI). The patients whose tumors had strong VEGF-C expression and low AI underwent a poorer prognosis than did those with weak VEGF-C expression and high AI.

CONCLUSION

VEGF-C expression is closely related to invasive phenotype and affects the patient's survival in ovarian carcinomas.

Involvement of LEU13 in interferon-induced refractoriness of human RSa cells to cell killing by X rays

Culture of human cells with human interferon alpha and beta (IFNA and IFNB) results in increased resistance of the cells to cell killing by X rays. To identify candidate genes responsible for the IFN-induced X-ray resistance, we searched for genes whose expression levels are increased in human RSa cells treated with IFNA, using an mRNA differential display method and Northern blotting analysis. RSa cells, which showed increased survival (assayed by colony formation) after X irradiation when they were treated with IFNA prior to irradiation, showed increased expression levels of LEU13 (IFITM1) mRNA after IFNA treatment alone. In contrast, IF(r) and F-IF(r) cells, both of which are derived from RSa cells, showed increased X-ray resistance and high constitutive LEU13 mRNA expression levels compared to the parental RSa cells. Furthermore, the IFNA-induced resistance of RSa cells to killing by X rays was suppressed by antisense oligonucleotides for LEU13 mRNA. LEU13, a leukocyte surface protein, was previously reported to mediate the actions of IFN such as inhibition of cell proliferation. The present results suggest a novel role of LEU13 different from that in the inhibition of cell proliferation, involved in IFNA-induced refractoriness of RSa cells to X rays.

HEC-1 cells

HEC-1 cell line was the first in vitro cell line of a human endometrial adenocarcinoma which enabled us to perform research work on the endometrium and endometrial carcinoma at a simplified cellular system, contributing cell and molecular biological studies on endometrial carcinoma. Once a cell line is established, it provides a stable experimental system that facilitates and progresses in the study of the tissues and/or neoplasias from which they are derived. In this article we report how HEC-1 cells have been established and cleared the proposed requirements to characterize the established cell line. Also to show the usefulness of the cell line for research work, once it was established, we illustrate these concepts by recalling results obtained with HEC-1 cells and reviewing the literature on what has been achieved by using these cells.

Inhibition of metastases by anticoagulants

Metastasis involves several distinct steps, including one in which the tumor cell, after entry into the bloodstream, comes to rest in a capillary located at the distant site where a metastatic tumor will ultimately form. Components of the blood-clotting pathway may contribute to metastasis by trapping cells in capillaries or by facilitating adherence of cells to capillary walls. Conceivably, anticoagulants could interfere with this step in the metastatic process. In this review, we have summarized current knowledge on the interaction of malignant cells, clotting factors, and anticoagulants. We used computerized (MEDLINE) and manual searches to identify studies done in humans, in animals, and in in vitro systems that were published in English between 1952 and 1998. We found many reports that the formation of metastatic tumors could be inhibited by heparin, a vitamin K antagonist (warfarin), and inhibitors of platelet aggregation (prostacyclin and dipyridamole). Despite these encouraging preliminary results and a compelling biochemical rationale, only limited information exists on the clinical use of anticoagulants for the prevention or treatment of metastatic cancer because there have been so few controlled and prospectively randomized studies on this topic. In view of the preliminary results, anticoagulants may hold promise for the prevention and treatment of metastases. We believe that larger controlled investigations are strongly warranted to evaluate the clinical potential of anticoagulants for the prevention and treatment of metastases in humans.

Detection of serum factors enhancing cell mutability from lung cancer patients by application of hypermutable human RS cells

A search for serum factors that modulate the mutability of human cells has been attempted in the peripheral blood of lung cancer patients. Factors were separated by dye-ligand chromatography and first identified as those exhibiting the ability to enhance the frequency of drug-resistance mutations in human RSa cells. The frequency was assessed by estimation of the cloning efficiency of mutant cells resistant to ouabain-mediated cell killing (OuaR) after irradiation with far-ultraviolet light (UV, mainly 254-nm wavelength). Pre-culture of cells with medium containing the factors prior to UV irradiation led to about a 19- to 37-fold increase in the OuaR mutation frequency compared with that of cells irradiated but not treated with the factors. The enhancing activity was detected in the serum of all 7 lung cancer patients, although the serum itself, which had not been treated with chromatography, had little or no enhancing activity in all patients. No enhancing activity was detected in serum preparations from healthy donors. The enhancing activity of lung cancer serum factors on UV-induced mutagenicity was next confirmed by detecting an enhancement of K-ras codon 12 base substitution mutations in human RSb cells, as analyzed by polymerase chain reaction (PCR) and differential dot-blot hybridization. Our results, together with previous findings on suppression of mutagen-induced mutagenicity by human interferons, suggest the existence of extracellular factors that modulate the mutability of human cells.

Enhancement of XPG mRNA expression by human interferon-beta in Cockayne syndrome cells

Using PCR-differential display, we have searched for genes expressed specially in human interferon (HuIFn)-beta-treated Cockayne syndrome (CS) fibroblast cells. Eighteen expressed genes induced by HuIFN-beta were identified, the sequences of seven of which were highly homologous to previously cloned sequences. The cDNAs of six of these seven clones were similar to expression tagged sequences from unknown genes in databases and the remaining one was identical to the cDNA of the xeroderma pigmentosum XPG gene. These results, together with our previous finding of increased resistance to ultraviolet (UV) cell-killing of CS cells pretreated with HuIFN-beta prior to UV irradiation suggest that XPG might be one of the genes possibly involved in the HuIFN-beta-induced UV-resistance.

UV-induced mutations affecting codon 12 of the K-ras gene are suppressed by interferon-alpha in human RSa cells

K-ras gene sequences mutant at codon 12 were recovered following differential dot-blot hybridization of genomic DNA from human RSa cells up to 12 days after the cells had been irradiated with far-UV (principally 254 nm). By contrast, no mutant codon 12 sequences were recovered from cells which had been treated with 50 IU/ml human interferon (HuIFN)-alpha for 24 h prior to their UV exposure. HuIFN-alpha treatment in combination with anti-HuIFN-alpha antibody did not lead to the loss of mutant sequences. However, culture of interferon-pretreated cells with medium containing the protease inhibitor antipain (0.01 mM) for 6 h immediately after UV irradiation led to the recovery of mutant codon 12 sequences. Thus, while treatment with HuIFN-alpha appeared to prevent any UV-induced mutations affecting codon 12 of the K-ras gene from being recovered, the putative antipain-sensitive protease responsible for this suppressive affect appeared to be significantly affected by the protease inhibitor antipain.

Hypomutable potential accompanying interferon-alpha resistance in a human cell line, IFr, derived from interferon-alpha-sensitive and hypermutable RSa cells

A human cell line, IFr, established from RSa cells, is a variant with increased resistance to cell proliferation inhibition (CPI) by human interferon (HuIFN)-alpha. The parent RSa cells are also hypermutable after irradiation with far-ultraviolet light (UV), as assessed by two different methods: cloning efficiency of ouabain-resistant (OuaR) mutants and K-ras codon 12 mutation in genomic DNA identified by polymerase chain reaction (PCR) following differential dot-blot hybridization. In the present study, IFr cells were found to be hypomutable: Less than 1 OuaR mutant per 10(4) surviving cells after UV (0-12 J/m2), in contrast to 1-53 OuaR mutants per 10(4) survivors in RSa cells, and no-detectable K-ras codon 12 mutation at any doses tested. However, IFr cells, when cultured with medium containing the protease inhibitor antipain after UV irradiation showed hypermutability to almost the same extent as RSa cells, as determined by both phenotypic and genetic mutation analyses. These results, together with the previous finding of antipain-sensitive protease induction in UV-irradiated or HuIFN-alpha-treated IFr cells, suggest that antipain-sensitive proteases or cellular functions or both may be involved in not only HuIFN-alpha resistance but also hypomutability of IFr cells.

Dipyridamole combined with tumor necrosis factor-alpha enhances inhibition of proliferation in human tumor cell lines

In the search for cytokines whose antiproliferative action could be enhanced by combination with dipyridamole, 2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido[5,4-d]pyrim idine, the combination of tumor necrosis factor-alpha (TNF-alpha) with this agent was evaluated in various human tumor cell lines. Inhibition of the proliferation of human melanoma cell lines MM-1CB and HMV-1 by TNF-alpha (1-10(2) U/ml) was enhanced in culture dishes by combination treatment with dipyridamole (0.1-10 microM). The enhancement effect was also detected in other tumor cell lines: T98 (glioma), SCC-1CB (squamous cell carcinoma), HAC-2 (ovarian clear-cell carcinoma), HLE (hepatoma), HEC-1 (endometrial adenocarcinoma) and HOC-21 (ovarian serous cystadenocarcinoma). The incorporation of [14C]amino acids and [3H]uridine into acid-insoluble cell materials in the combination-treated cells was not significantly different from that in cells treated with TNF-alpha or dipyridamole. However, the incorporation of [3H]thymidine was specifically inhibited in all cell lines examined after more than 12 h of the TNF-alpha and dipyridamole combination treatment, although neither agent alone inhibited this incorporation. On the other hand, the growth of tumors induced by the injection of MM-1CB and HMV-1 cells into nude mice was more markedly inhibited by the subcutaneous administration of TNF-alpha in combination with orally administered dipyridamole than by either agent alone. The results presented suggested that dipyridamole is beneficial in assuring the effectiveness of anti-cancer cytokine therapy.

Human cell clones, RSa and UVr-1, differing in their capability for UV-induced virus reactivation and phenotypic mutation

UVr-1 is a human cell clone established as a variant with increased resistance to cell killing by ultraviolet light (UV, principally 254 nm wavelength) from a UV-sensitive cell clone, RSa. Both cells have been characterized to have much the same capacity of UV-induced DNA repair synthesis in whole cells, and the parent RSa cells were recently found to be hypermutable. In the present study UVr-1 cells were characterized in comparison RSa cells with respect to UV-induced virus reactivation and phenotypic mutation. Survival levels of UV-irradiated vaccinia virus and herpes simplex virus type 1 (HSV-1) were much the same in logarithmically proliferating UVr-1 and RSa cells. Correlated with these host cell reactivation levels, the same extent of UV-induced DNA repair replication synthesis was observed in isolated nuclei of the two cell clones. Enhancement of survival levels of UV-irradiated HSV-1 was detected when proliferating RSa cells were irradiated with UV prior to the virus infection. In contrast, this enhanced virus reactivation (EVR) was not detected in similarly irradiated and infected UVr-1 cells. As for phenotypic mutation frequencies assessed by the cloning efficiency of cells with increased resistance to ouabain cell killing (OuaR), OuaR mutants were not obtained from UVr-1 cells either with or without UV irradiation. When the proliferation of cells was synchronized, both EVR and OuaR mutations were detected in RSa cells irradiated with UV at any cell cycle phase, being greatest in the later half of the G1 phase. However, there was no detectable EVR or mutation in any phase of synchronous UVr-1 cells. The hypomutability of UVr-1 cells and hypermutability of RSa cells in a G1 cell cycle phase was also found even if 4-nitroquinoline 1-oxide was used as a mutagen or mutant cells with increased resistance to 6-thioguanine cell killing were estimated.