Lack of correlation between interferon induction and antitumour effect of poly I-poly C

Replicase-based plasmid DNA shows anti-tumor activity

Background

Double stranded RNA (dsRNA) has multiple anti-tumor mechanisms. Over the past several decades, there have been numerous attempts to utilize synthetic dsRNA to control tumor growth in animal models and clinical trials. Recently, it became clear that intracellular dsRNA is more effective than extracellular dsRNA on promoting apoptosis and orchestrating adaptive immune responses. To overcome the difficulty in delivering a large dose of synthetic dsRNA into tumors, we propose to deliver a RNA replicase-based plasmid DNA, hypothesizing that the dsRNA generated by the replicase-based plasmid in tumor cells will inhibit tumor growth.

Methods

The anti-tumor activity of a plasmid (pSIN-β) that encodes the sindbis RNA replicase genes (nsp1-4) was evaluated in mice with model tumors (TC-1 lung cancer cells or B16 melanoma cells) and compared to a traditional pCMV-β plasmid.

Results

In cell culture, transfection of tumor cells with pSIN-β generated dsRNA. In mice with model tumors, pSIN-β more effectively delayed tumor growth than pCMV-β, and in some cases, eradicated the tumors.

Conclusion

RNA replicase-based plasmid may be exploited to generate intracellular dsRNA to control tumor growth.

Localized irradiation of tumors prior to synthetic dsRNA therapy enhanced the resultant anti-tumor activity

BACKGROUND AND PURPOSE

Despite the potent tumoricidal activity of the synthetic dsRNA in culture, its in vivo anti-tumor activity has proven to be limited. We sought to devise and validate a new strategy to improve the in vivo anti-tumor activity by integrating localized irradiation into dsRNA therapy.

MATERIALS AND METHODS

Using a mouse lung cancer model and a mouse melanoma model in immuno-competent mice or athymic nude mice, we evaluated the combined anti-tumor activity using a synthetic dsRNA, polyinosine-cytosine (poly(I:C)).

RESULTS

Localized irradiation of tumors prior to the poly(I:C) therapy significantly delayed the tumor growth as compared to monotherapies using the radiation or poly(I:C) alone. The poly(I:C) enhanced the tumor response to radiation with a dose modification factor as large as 20. The combined effect was synergistic only in immuno-competent mice with highly immunogenic tumors. The anti-tumor activity of the combination therapy was significantly impaired when the type I interferons in the mice were neutralized.

CONCLUSIONS

This combination modality may represent a promising approach to exploit synthetic dsRNA in cancer therapy and to enhance tumor response to radiation. T cell-mediated immunity was likely responsible for the combined synergistic effect. Type I interferons contributed significantly to the combined anti-tumor activity.

Inflammation and breast cancer. Inflammatory component of mammary carcinogenesis in ErbB2 transgenic mice

This review addresses genes differentially expressed in the mammary gland transcriptome during the progression of mammary carcinogenesis in BALB/c mice that are transgenic for the rat neu (ERBB2, or HER-2/neu) oncogene (BALB-neuT^664V-E mice). The Ingenuity knowledge database was used to characterize four functional association networks whose hub genes are directly linked to inflammation (specifically, the genes encoding IL-1β, tumour necrosis factor, interferon-γ, and monocyte chemoattractant protein-1/CC chemokine ligand-2) and are increasingly expressed during such progression. In silico meta-analysis in a human breast cancer dataset suggests that proinflammatory activation in the mammary glands of these mice reflects a general pattern of human breast cancer.

Inhibitory effect of polynucleotides on solid tumor produced in mice by Ehrlich ascites cancer cells

Solid tumors produced in mice by Ehrlich ascites cancer cells were completely regressed by treatment with the copolymer of polyriboinosinic acid-polyribocytidylic acid (poly (I):(C)) when 200 microgram of this compound was intravenously injected 3 times a week for 3-4 weeks, starting 7-8 days after transplantation of the tumor. Although the first injection of poly (I):(C) caused hyporeactivity to re-induction of IFN, the subsequent 6 doses stimulated the formation of IFN at 3685 units/ml on average after each injection, strongly suggesting that IFN plays a role in the antitumoral effect of poly (I):(C).

Role of endogenous interferon in the anti-tumor effect of poly I-C and statolon as demonstrated by the use of anti-mouse interferon serum

We have determined the effect of sheep anti-mouse interferon globulin on the anti-tumor effects of poly I-C, statolon, tilorone, pyran copolymer and BCG in mice inoculated with Ehrlich ascites or L 1210 lymphoma cells. Whereas the anti-tumor effects of poly I-C and statolon were nulified when mice were injected with immunoglobulins, the anti-tumor effects of pyran copolymer and BCG were not modified by this treatment. We conclude that interferon mediates the anti-tumor activity of poly I-C and statolon in these experimental systems. It is suggested that anti-interferon serum provides a direct method of determining whether other biologic effects attributed to viruses, poly I-C, statolon, tilorone, pyran copolymer (and possibly other interferon inducers) are mediated or not by interferon.