Interferon‐α and antisense K‐ras RNA combination gene therapy against pancreatic cancer

Abstract

Interferon alpha (IFN-alpha) is used worldwide for the treatment of a variety of cancers. For pancreatic cancer, recent clinical trials using IFN-alpha in combination with standard chemotherapeutic drugs showed some antitumor activity of the cytokine, but the effect was not significant enough to enlist pancreatic cancer as a clinically effective target of IFN-alpha. In general, an improved therapeutic effect and safety are expected for cytokine therapy when given in a gene therapy context, because the technology would allow increased local concentrations of this cytokine in the target sites. In this study, we first examined the antiproliferative effect of IFN-alpha gene transduction into pancreatic cancer cells. The expression of IFN-alpha effectively induced growth suppression and cell death in pancreatic cancer cells, an effect which appeared to be more prominent when compared with other types of cancers and normal cells. Another strategy we have been developing for pancreatic cancer targets its characteristic genetic aberration, K-ras point mutation, and we reported that the expression of antisense K-ras RNA significantly suppressed the growth of pancreatic cancer cells. When these two gene therapy strategies are combined, the expression of antisense K-ras RNA significantly enhanced IFN-alpha-induced cell death (1.3- to 3.5-fold), and suppressed subcutaneous growth of pancreatic cancer cells in mice. Because the 2',5'-oligoadenylate synthetase/RNase L pathway, which is regulated by IFN and induces apoptosis of cells, is activated by double-strand RNA, it is plausible that the double-strand RNA formed by antisense and endogenous K-ras RNA enhanced the antitumor activity of IFN-alpha. This study suggested that the combination of IFN-alpha and antisense K-ras RNA is a promising gene therapy strategy against pancreatic cancer.

Adenovirus-mediated interferon α gene transfer induces regional direct cytotoxicity and possible systemic immunity against pancreatic cancer

“…Although the mouse IFN-a did not show a direct antiproliferative effect against human pancreatic cancer cells in vitro, the mouse IFN-a gene transduction into pancreatic cancer xenografts showed significant inhibition of tumour growth, which was attributed to an IFN-ainduced stimulation of NK cells. This study together with our previous report showing a characteristically high sensitivity of pancreatic cancer cells to the direct cytotoxicity of IFN-a transgene expression (Hatanaka et al, 2004) suggests that IFN-a gene therapy is a promising therapeutic strategy for pancreatic cancer, due to its dual mechanisms of antitumour activities.…”

“…Although the injection of 2.5 Â 10 8 PFU of AdCA-AP showed a slight expression of IFN-a at day 1, which may be a naïve reaction in response to viral infection, the IFN-a expression returned to the base line (o300 IU g À1 ) by day 9. The subcutaneous tumour showed approximately 100 -1000-fold higher IFN-a levels than the serum did (Figure 2), confirming a markedly increased IFN-a concentration in the subcutaneous tumour with little leakage into the serum (Hatanaka et al, 2004). After the intratumoral injection of recombinant IFN-a protein (3 Â 10 5 IU g À1 ), the concentration of IFN-a was 6097130 IU g À1 at day 1 and returned to the base line by day 3, which indicated the injected recombinant IFN-a protein was rapidly degraded in the tumour.…”

“…In fact, it has been reported that direct IFN-a gene transfer into tumours suppressed growth of various cancers such as breast cancer, prostate cancer, renal cancer, hepatocellular carcinoma, basal cell carcinoma and leukaemia (Zhang et al, 1996;Coleman et al, 1998;Hottiger et al, 1999;Iqbal Ahmed et al, 2001). Although no study of IFN-a gene transfer against pancreatic cancer had been reported, we recently found that the expression of IFN-a effectively induced growth suppression and cell death in pancreatic cancer cells, an effect that appeared to be more prominent than in other types of cancers and normal cells (Hatanaka et al, 2004).…”

“…We previously reported that an intratumoral injection of an adenoviral vector expressing the human IFN-a gene, AxCA-IFN (2.5 Â 10 8 PFU), effectively suppressed the growth of nude mouse subcutaneous tumours of the AsPC-1 human pancreatic cancer cells (Hatanaka et al, 2004). In this study, the superior antitumour effect of the IFN-a gene therapy over the recombinant IFN-a protein therapy was evaluated between the single injection of 1.0 Â 10 8 PFU of AxCA-IFN and 3 Â 10 5 IU g À1 of recombinant IFN-a protein, which corresponds to the top level achieved by the 1.0 Â 10 8 PFU of AxCA-IFN infection as shown in Figure 2.…”

“…This may be the major reason why the previous trials based on the conventional IFN-a therapy failed to show an adequate antitumour effect. By contrast, improved therapeutic effect and safety are expected for IFN-a gene transfer, because it allows an increased and sustained local concentration of this cytokine in the target sites while minimising unnecessary systemic distribution (Suzuki et al, 2003;Hatanaka et al, 2004). In fact, it has been reported that direct IFN-a gene transfer into tumours suppressed growth of various cancers such as breast cancer, prostate cancer, renal cancer, hepatocellular carcinoma, basal cell carcinoma and leukaemia (Zhang et al, 1996;Coleman et al, 1998;Hottiger et al, 1999;Iqbal Ahmed et al, 2001).…”