Adeno-associated virus vector-mediated systemic delivery of IFN-beta combined with low-dose cyclophosphamide affects tumor regression in murine neuroblastoma models.

PURPOSE: Type I IFNs (IFN-alpha/beta) have shown significant antitumor activity in preclinical models but limited efficacy and significant toxicity in clinical trials. We hypothesized that the antitumor activity of type I IFNs could be enhanced by chronic, low-dose systemic delivery and sought to test this in murine neuroblastoma models. EXPERIMENTAL DESIGN: Continuous liver-generated expression of human IFN-beta (hINF-beta) was achieved through a gene therapy-mediated approach using adeno-associated virus vectors encoding hIFN-beta (AAV hINF-beta). Orthotopic localized retroperitoneal and disseminated models of neuroblastoma were established using three different xenografts. Immunohistochemical analysis and ELISA were used to evaluate the antiangiogenic effect of therapy. RESULTS: The development of both localized orthotopic (retroperitoneal) and disseminated neuroblastoma was prevented in all mice expressing hINF-beta. Continued growth of established retroperitoneal tumors, treated with AAV hINF-beta as monotherapy, was significantly restricted, and survival for mice with established, disseminated disease was significantly prolonged following administration of AAV hINF-beta. Analysis of treated tumors revealed a significant antiangiogenic effect. Mean intratumoral vessel density was diminished and expression of the angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor were both decreased. Finally, combination therapy in which AAV hIFN-beta was used together with low-dose cyclophosphamide resulted in regression of both established retroperitoneal and disseminated disease. CONCLUSIONS: AAV-mediated delivery of hIFN-beta when used as monotherapy was able to restrict neuroblastoma growth due in part to inhibition of angiogenesis. When used in combination with conventional chemotherapy, AAV hIFN-beta was able to effect complete tumor regression.     

Therapeutic effect of intravenous delivery of lipoplexes containing the interferon-beta gene and poly I: poly C in a murine lung metastasis model

We have evaluated and compared the efficacy of systemic administration of lipoplex formulations containing plasmids encoding IFN-beta or IFN-gamma, and a synthetic double-strand RNA poly I:poly C (pI:pC), a type I IFN inducer, in a lung metastasis model in which colon carcinoma CT-26 cells were inoculated intravenously into immunocompatible mice. Injection of lipoplexes containing plasmid DNA, regardless of IFN gene insertion, stimulated a transient increase in the serum concentration of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha and IFN-gamma, while injection of lipoplexes containing pI:pC led to a low level of TNF-alpha and undetectable IFN-gamma production. Furthermore, injection of these lipoplexes containing plasmids resulted in the production of a mixture of type I and type II IFNs, partly derived from the inserted IFN genes, in lung tissue cultures. In tumor-prophylactic experiments, intravenous injection of lipoplexes containing plasmid, regardless of IFN gene insertion, showed a significant reduction in lung metastatic nodules probably due to proinflammatory cytokines such as TNF-alpha and IFN-gamma nonspecifically induced by the CpG motifs in the plasmid and the type I IFNs produced. On the other hand, the antimetastatic effect of pI:pC-lipoplex seemed to be due mainly to IFN-beta induced by pI:pC. In established lung metastasis experiments, a single intravenous administration of lipoplexes containing IFN-beta gene or pI:pC, but not other lipoplexes, showed a significant therapeutic effect on the tumor metastasis: reduction in tumor nodules and prolongation of survival time of tumor-burden mice. The therapeutic effects were specifically impaired by anti-IFN-beta antibody treatment, indicating that IFN-beta produced by the lipoplexes played an important role in the suppression of established metastatic lung tumors. Thus, the local IFN-beta in the lung delivered by intravenous administration of lipoplex containing IFN-beta gene or pI:pC may be a convenient and useful method of inhibiting established metastatic lung tumors.     

Stronger growth-inhibitory effect of interferon (IFN)-beta compared to IFN-alpha is mediated by IFN signaling pathway in hepatocellular carcinoma cells

Interferon (IFN) is a promising drug for prevention and treatment of hepatocellular carcinoma (HCC) in combination with chemotherapeutic agents. We previously reported that the spectra of antiproliferative activity and synergistic effect of IFN-beta when combined with anticancer drugs are more potent than those of IFN-alpha in HCC cells. However, the mechanism of the diverse antitumor effects of the IFNs is not understood yet. We studied the expression of IFN alpha receptor 2 (IFNAR2), STATs, and IFN-alpha, IFN-beta's growth-inhibitory effect, signal transduction and binding to IFNAR2 on three HCC cell lines and a tumor xenografted mouse model (12 animals/group). From the results, IFN-beta showed a significantly stronger growth-inhibitory effect than IFN-alpha on the HuH7 cell line (expressing low IFNAR2), however it was similarly high on PLC/PRF/5 and weak on HLE. In the nude mouse tumor xenograft model, IFN-beta injection significantly suppressed tumor volume relative to vehicle injection, while IFN-alpha showed weaker growth-inhibition. IFN signal transduction (phosphorylated-STAT1, 3) induced by IFN-beta was higher than that by IFN-alpha in HuH7 and tumor xenografts. Pretreatment of hepatoma cells with anti-IFNAR2 antibody blocked the IFN signaling, more for IFN-alpha. IFN-alpha's antiproliferative effect was reduced by the antibody in lower concentrations compared to that of IFN-beta. Taken together, the HCC cells that express low IFNAR2 and are resistant to IFN-alpha were sensitive to the growth-inhibitory effect of IFN-beta, which might be mediated by stronger IFN signal transduction and distinct binding to IFNAR compared to IFN-alpha.     

Inhibition of angiogenesis by interferons: effects on tumor- and lymphocyte-induced vascular responses

Interferons (IFNs) have established antitumor action; the mechanism underlying this effect is, however, not yet clear. To probe the possible contribution of inhibition of angiogenesis, we have assessed angiogenesis in the mouse initiated by either human or murine tumor cell lines. Whether test cells were inoculated in the dermis or tumor fragments were grafted onto the cornea, tumor-induced angiogenesis (TIA) was inhibited by IFNs. TIA was also inhibited by the potent IFN inducer polyriboinosinic-polyribocytidylic acid. The effect of IFN was species specific; human IFNs inhibited human tumors and mouse IFNs inhibited murine tumors. This effect suggested that in contrast to other angiogenesis inhibitors, IFNs modulated the signal for angiogenesis produced by the tumor cells. Tumor cells treated in vitro with homologous IFN were significantly (P less than 0.005) less competent to initiate angiogenesis than were untreated cells. Inhibition of angiogenesis was achieved whether vascular response was assessed 1 or 3 days after tumor cell inoculation, suggesting that antiangiogenesis activity was independent of the antiproliferative effects of IFNs. To further substantiate this, L1210 leukemia cells, resistant to the antiproliferative effects of IFNs, were treated with 500 units/ml IFN-beta. IFN had no effect on their proliferation, but in four separate experiments, L1210R cells were impaired in their ability to induce angiogenesis. Thus, inhibition of TIA by IFNs was species specific, occurred at least partly by modulation of the signal inducing angiogenesis, and was expressed in the absence of antiproliferative effects. IFNs also inhibited immunologically induced angiogenesis, whether initiated by allogeneic lymphocytes (LIA) or by the mouse's own T-cells in response to an exogenous antigen (sheep RBC). LIA was markedly suppressed by treatment of host mice with homologous IFN-beta. For example, mean vessel counts induced by allogeneic mouse lymphocytes were decreased from 22.8 +/- 1.4 (SE) to 12.5 +/- 0.8 (P less than 0.0001); mouse IFN-beta had no corresponding effect on xenogeneic human lymphocytes (mean vessel counts decreased to 21.7 +/- 2.6 from 22.7 +/- 2.0). Treatment with human IFN-alpha, -beta, or -gamma in vitro or host mice in vivo reduced the ability of inoculated human peripheral blood lymphocytes to initiate xenogeneic LIA. Inhibition of LIA required a lower dose and/or a shorter incubation period than that needed to modulate TIA. Treatment of the donor of the allogeneic spleen cells in vivo with murine IFN or inducers also resulted in lesser LIA.(ABSTRACT TRUNCATED AT 400 WORDS)     

Selective interferon-induced enhancement of tumor-associated antigens on a spectrum of freshly isolated human adenocarcinoma cells

Freshly isolated cells from patients with pleural or peritoneal effusions cytologically diagnosed as adenocarcinoma (n = 43), malignant nonepithelial neoplasms (n = 10), and benign (n = 8) were analyzed for expression of constitutive levels of the tumor antigens TAG-72 [recognized by monoclonal antibody (MAb) B72.3] and carcinoembryonic antigen (CEA) (recognized by MAb COL-4) as well as the class I and class II major histocompatibility (MHC) antigens, and the ability of human interferons (Hu-IFNs) to enhance cell surface expression of those antigens as measured by MAb binding. Both type I and type II IFNs enhanced the expression of TAG-72 and CEA and altered the level of expression of the MHC antigens. Comparative studies of three different Hu-IFNs (IFN-alpha A, IFN-beta ser, and IFN-gamma) revealed that IFN-gamma was the most potent in augmenting either B72.3 or COL-4 binding. Unlike the IFN-gamma -mediated induction of the class II human leukocyte antigens, the change in tumor antigen expression consisted of enhanced constitutive antigen expression; de novo induction of either TAG-72 or CEA could not be achieved by either type I or type II IFN. Of 43 effusions isolated from different adenocarcinoma patients, 42 (97.7%) expressed either CEA or TAG-72, and treatment with Hu-IFN increased the level of expression of either antigen in 36 of 42 samples (85.7%). These studies demonstrate the augmentation of tumor-associated antigens on human carcinoma cells isolated from serous effusions by Hu-IFNs which may be used to enhance the targeting of conjugated MAbs to human carcinoma lesions.     

Preferential induction of apoptosis by interferon (IFN)-beta compared with IFN-alpha2: correlation with TRAIL/Apo2L induction in melanoma cell lines.

On the basis of in vitro inhibition of tumor cell growth, IFNs have been generally considered to be antiproliferative proteins. To probe further the potential mechanisms of the antitumor effects of IFNs, we have assessed apoptosis in response to IFN-alpha2 and IFN-beta in cell lines of varied histologies, with a focus on melanomas. Many of the cell lines tested underwent apoptosis in response to IFN-beta, as assessed both by Annexin V and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. In general, IFN-beta had greater growth inhibitory and proapoptotic effects than IFN-alpha2 on all cell lines. The melanoma cell line WM9, sensitive to growth inhibition by IFNs, had a greater degree of apoptosis than A375 melanoma cells, which were largely resistant to antigrowth effects of IFNs. IFN-beta-induced apoptosis was dependent on activation of the caspase cascade with cleavage of caspases 3, 8, and 9 and of the caspase 3 substrate, poly(ADP-ribose) polymerase. Caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl keton or benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl keton, inhibited IFN-beta-induced apoptosis. Other changes associated with apoptosis, including the movement of cytochrome c from mitochondria to cytoplasm and DNA fragmentation, were also identified in response to IFN-beta. Apo2L ligand [tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)] was one of the early genes induced by IFN-beta in apoptosis-sensitive WM9 cells. Other sensitive melanoma cell lines had a similar IFN-beta-specific induction of TRAIL. Neutralizing antibody to TRAIL inhibited IFN-beta-induced apoptosis in WM9 cells. In resistant A375 cells, IFN-beta did not induce TRAIL/Apo2L expression. Thus, induction of TRAIL by IFNs in some tumor types may initiate the apoptotic cascade. This study offers another mechanism for the antitumor effects of IFNs.     

Antiproliferative and immunomodulatory actions of beta-interferon and double-stranded RNA, individually and in combination, on human bladder tumor xenografts in nude mice

A cell line, RT4, derived from a human transitional cell carcinoma of the bladder, was grown as a xenograft in athymic mice. The growth of the xenografts was inhibited by beta-interferon (IFN-beta), polyriboinosinic acid.polyribocytidilic acid, the mismatched double-stranded RNA analogue r(I)n . r(C12,U)n, and to a lesser extent recombinant IFN-beta, when treatment was initiated at the time of tumor inoculation. In contrast, the growth rate of established tumors, approximately 6 mm in diameter at the initiation of therapy, was inhibited by both double-stranded RNAs, but not natural IFN-beta, indicating a possible tumor size dependence on the effectiveness of IFN-beta. Combinations of natural or recombinant IFN-beta with either polyriboinosinic acid.polyribocytidilic acid or r(I)n.r(C12,U)n gave an antagonistic effect regardless of tumor mass at the initiation of treatment. This antagonism could be overcome by alternating r(I)n. r(C12,U)n and natural IFN-beta treatment. Natural killer cell activity against RT4 cells in culture was augmented in the spleens of mice treated with r(I)n.r(C12,U)n, but not in those treated with natural IFN-beta. RT4 cells treated in culture with IFN-beta, however, were significantly less efficient as targets for natural killer cells from r(I)n.r(C12,U)n-treated and control spleens. These results indicate that: the effectiveness of IFN-beta may be related to the tumor mass; double-stranded RNAs appear to work, at least partially, in an indirect, immunomodulatory manner; combination therapy can yield an antagonistic rather than an additive or synergistic antitumor effect; and strategic scheduling can overcome the antagonistic effect of combination therapy.     

Effective induction of antiglioma cytotoxic T cells by coadministration of interferon-beta gene vector and dendritic cells

As type I interferons (IFNs) enhance the stimulatory activity of dendritic cells (DCs), we hypothesized that transfection of glioma cells with the IFN-beta gene in the presence of DCs would provide particularly effective antitumor activity by both facilitating apoptosis of glioma cells and presenting the resulting glioma antigens to T cell by DCs, thereby inducing specific T-cell responses against glioma cells. A mouse glioma cell line 203G was first transfected with cDNA encoding IFN-beta using cationic liposomes, then cocultured with syngeneic bone marrow-derived DCs and na?ve splenic T cells. The 203G cells were almost completely killed following 96-hour coculture with DCs and T cells, and strong tumor-specific cytotoxic T-lymphocyte (CTL) activity accompanied by high level interleukin (IL)-12 and IFN-gamma production was observed in culture. In addition, omission of either IFN-beta gene delivery, DCs or T cells from the coculture completely abrogated the induction of the CTL activity, suggesting that the combination of these components was required to elicit an optimal effect. On the basis of these in vitro data, syngeneic animals bearing subcutaneous 203G tumors received intratumoral injections of IFN-beta gene and DCs. Suppression of the tumor growth by this combinational therapy was superior to treatment with DC or IFN-beta gene solely. This combination may constitute a new therapeutic strategy to induce potent antiglioma immune responses.     

Bilateral breast metastases from ewing sarcoma of the femur

We report a case of bilateral breast metastases from Ewing sarcoma of the femur. A 40-year-old woman presented with Ewing sarcoma of the left thigh, treated by complete surgical exeresis and chemotherapy. Secondary, a large tumor appeared in the left breast. Bone scintigraphy, chest, and abdominal computed tomographic scan were normal. A breast biopsy found a malignant tumor composed of small round cells consistent with the initial diagnosis. After the first cycle of chemotherapy, a tumor was discovered in the controlateral breast. After 5 cycles, residual tumors persisted in the 2 breasts. Tumor exeresis was performed and found bilateral breast metastases of Ewing sarcoma. Because of the early recurrence of the left breast tumor, segmentectomy of the right breast and left mastectomy were performed. The histopathological analysis confirmed Ewing sarcoma metastases in the left breast. Despite local radiotherapy, the clinical course was marked by lumbar bone metastasis, local chest evolution, and progression of the disease. Metastases to the breast by extramammary malignant neoplasms are unusual. Sarcoma is an extremely rare cause of breast metastases and our case is the first report of breast metastases from Ewing sarcoma.     

Angiogenesis and vascular targeting in Ewing sarcoma

Ewing sarcoma is the second most common type of bone cancer in children and young adults. In recent years, the mechanisms by which these tumors develop and maintain their vascular supply have been elucidated. Additional work has demonstrated that inhibition of angiogenic pathways or disruption of established vasculature can attenuate the growth of Ewing sarcoma mouse xenografts. Early clinical data suggest that these results also may extend to patients with Ewing sarcoma who are treated with antiangiogenic or antivascular therapies. For the current review, the authors summarized the available data supporting this approach. Cancer 2010. © 2009 American Cancer Society.     

Continuous inhibition of epidermal growth factor receptor phosphorylation by erlotinib enhances antitumor activity of chemotherapy in erlotinib-resistant tumor xenografts

Erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor, has been shown to have benefits for non-small cell lung cancer and pancreatic cancer patients; however, almost all patients develop progressive disease during the therapy. On the other hand, it has been reported that a tumor continues to express epidermal growth factor receptor even after developing progressive disease. To demonstrate the clinical relevance of erlotinib treatment after progressive disease, we investigated whether continuous administration of erlotinib in combination with chemotherapy has a useful effect on progressive disease development during erlotinib treatment. For this purpose, we examined the antitumor effect of a combination therapy of a chemotherapeutic agent with erlotinib using two types of erlotinib-resistant tumor xenograft models: a non-small cell lung cancer model, in which EBC-1, H1975 and HCC827TR3 tumors were implanted, and an HPAC pancreatic cancer cell xenograft which generates erlotinib-resistant tumors in vivo. As a result, the combination therapy showed a significantly higher antitumor activity compared with chemomonotherapy in all xenograft models except the H1975 xenografts. Furthermore, erlotinib alone suppressed the phosphorylation of epidermal growth factor receptor in HPAC tumors and the two non-small cell lung cancer cell lines other than H1975. Therefore, combination therapy which uses erlotinib can be considered effective if epidermal growth factor receptor phosphorylation is inhibited by erlotinib, even in erlotinib-resistant tumor xenograft models. Our results suggest that the continuous inhibition of epidermal growth factor receptor phosphorylation by erlotinib after progressive disease enhances the antitumor activity of chemotherapy.     

Effects of interferon beta on transcobalamin II-receptor expression and antitumor activity of nitrosylcobalamin

BACKGROUND: The ubiquitous plasma membrane transcobalamin II receptor (TC II-R) mediates uptake of cobalamin (Cbl; vitamin B12), an essential micronutrient. Tumors often require more Cbl than normal tissue, and increased Cbl uptake may result from increased TC II-R expression. To examine whether Cbl could therefore be used as a carrier molecule to target a chemotherapy drug, we tested an analogue of Cbl with nitric oxide as a ligand, nitrosylcobalamin (NO-Cbl). Because interferon beta (IFN-beta) has antitumor effects and increases expression of some membrane receptors, we examined whether it may enhance the effects of NO-Cbl. METHODS: Antiproliferative effects of NO-Cbl were assessed in 24 normal and cancer cell lines. Xenograft tumors of human ovarian cancer NIH-OVCAR-3 cells were established in athymic nude mice, and tumor growth was monitored after treatment with NO-Cbl and IFN-beta, both individually and concomitantly. TC II-R expression and apoptosis was monitored in vitro and in vivo. RNA protection assays and mitochondrial membrane potential assays were used to distinguish the extrinsic and intrinsic apoptotic pathways, respectively. RESULTS: Cancer cell lines were more sensitive to NO-Cbl (with ID(50)s [the dose that inhibits growth by 50%] as low as 2 microM) than normal cell lines (with ID(50)s of 85-135 microM). Single-agent NO-Cbl and IFN-beta treatment of NIH-OVCAR-3 xenografts induced tumor regression, whereas combination treatment induced tumor eradication. IFN-beta treatment increased TC II-R expression in vitro and uptake of [(57)Co]cobalamin in vivo. Compared with NIH-OVCAR-3 cells treated with NO-Cbl, cells treated with NO-Cbl and IFN-beta were more apoptotic and expressed higher mRNA levels of various apoptosis-associated genes. No changes in mitochondrial membrane potential were observed in cells treated with NO-Cbl. CONCLUSION: NO-Cbl inhibited tumor growth in vivo by activating the extrinsic apoptotic pathway. The increased expression of TC II-R induced by IFN-beta resulted in enhanced antitumor effects with NO-Cbl both in vitro and in vivo.     

Characteristics and oncologic outcomes of patients with Ewing sarcoma of the scapula

Background and objectivesEwing sarcoma is the second most common bone sarcoma of childhood. Ewing sarcomas of the scapula are rare, with little known about their characteristics and outcomes. In this study, we describe the demographic characteristics, tumor characteristics, and oncologic outcomes of patients with Ewing sarcoma of the scapula.MethodsThis is a retrospective case series of thirty-four patients treated at three urban hospitals between 1993 and 2014 for Ewing sarcomas affecting the scapula. Their demographic data, tumor characteristics, and oncologic outcomes are reported and contrasted with data on Ewing sarcoma described in the literature.ResultsPatients in our case series were 59% male. The average age at diagnosis was 16 years. 44% of patients had metastatic disease at presentation. 26% of patients had a tumor size >8 cm in largest dimension at diagnosis. 9 patients in our series had the t (11; 22) translocation present. Patients had a survival rate of 68% at five years. No patients had local recurrence of disease. Compared with findings reported in the literature concerning Ewing sarcoma affecting other locations, patients with Ewing sarcoma of the scapula were slightly older at time of diagnosis, had a lower percentage of tumors with size > 8 cm in largest dimension at presentation, and more commonly had metastatic disease at presentation. Patients in our cohort had a 5-year survival rate of 68%, which is higher than the rate of approximately 55% as reported in the general literature.ConclusionsIn this study, we describe a retrospective case series of thirty-four patients with Ewing sarcomas of the scapula. This is the largest case series to date of Ewing sarcoma affecting this location to our knowledge. These results will contribute to the understanding of the clinical profile and oncologic behavior of Ewing sarcomas affecting the scapula.     

Can taxanes provide benefit in patients with CNS tumors and in pediatric patients with tumors? An update on the preclinical development of cabazitaxel

Purpose

While first-generation taxanes are valuable treatment options for many solid tumors, they are limited by an inability to cross the blood–brain barrier (BBB) and by limited efficacy in pediatric patients. Following promising preclinical data for the next-generation taxane cabazitaxel, including activity in tumor models fully sensitive, poorly sensitive or insensitive to docetaxel, and its ability to cross the BBB, further preclinical studies of cabazitaxel relevant to these two clinical indications were performed.

Methods

Cabazitaxel brain distribution was assessed in mice, rats and dogs. Cabazitaxel antitumor activity was assessed in mice bearing intracranial human glioblastoma (SF295; U251) xenografts, and subcutaneous cell line-derived human pediatric sarcoma (rhabdomyosarcoma RH-30; Ewing’s sarcoma TC-71 and SK-ES-1) or patient-derived pediatric sarcoma (osteosarcoma DM77 and DM113; Ewing’s sarcoma DM101) xenografts. The activity of cabazitaxel–cisplatin combination was evaluated in BALB/C mice bearing the syngeneic murine colon adenocarcinoma, C51.

Results

Cabazitaxel penetrated rapidly in the brain, with a similar brain–blood radioactivity exposure relationship across different animal species. In intracranial human glioblastoma models, cabazitaxel demonstrated superior activity to docetaxel both at early (before BBB disruption) and at advanced stages, consistent with enhanced brain penetration. Compared with similar dose levels of docetaxel, cabazitaxel induced significantly greater tumor growth inhibition across six pediatric tumor models and more tumor regressions in five of the six models. Therapeutic synergism was observed between cisplatin and cabazitaxel, regardless of administration sequence.

Conclusions

These preclinical data suggest that cabazitaxel could be an effective therapy in CNS and pediatric tumors, supporting ongoing clinical evaluation in these indications.     

The efficacy of radiotherapy relies upon induction of type i interferon-dependent innate and adaptive immunity

The most widely held explanation for the efficacy of local radiotherapy (RT) is based on direct cytotoxicity to cancer cells through the induction of lethal DNA damage. Recent studies have shown that local ablative radiation of established tumors can lead to increased T-cell priming and T-cell-dependent tumor regression, but the underlying mechanism remains unclear. Here, we describe an essential role for type I IFN in local RT-mediated tumor control. We show that ablative RT increases intratumoral production of IFN-β and, more surprisingly, the antitumor effect of RT is abolished in type I IFN nonresponsive hosts. Furthermore, the major target of RT-induced type I IFN is the hematopoietic compartment. RT drastically enhances the cross-priming capacity of tumor-infiltrating dendritic cells (TIDC) from wild-type mice but not type I IFN receptor-deficient mice. The enhanced cross-priming ability of TIDCs after RT was dependent on autocrine production of type I IFNs. By using adenoviral-mediated expression of IFN-β, we show that delivery of exogenous IFN-β into the tumor tissue in the absence of RT is also sufficient to selectively expand antigen-specific T cells leading to complete tumor regression. Our study reveals that local high-dose RT can trigger production of type I IFN that initiates a cascading innate and adaptive immune attack on the tumor.     

Use of cyclooxygenase-2 inhibition to enhance the efficacy of immunotherapy

Antitumor effects of cyclooxygenase-2 (COX-2) inhibition have been reported in a wide variety of tumor models and in human cancers, both as chemoprevention and therapy. Human mesothelioma tumors have been shown to overexpress COX-2 and high levels of COX-2 protein have been demonstrated to be a prognostic factor, indicating poor outcome in this tumor. In this study, we determined that inhibition of COX-2 by oral administration of Rofecoxib significantly slowed but did not cure the growth of small tumors in mesothelioma-bearing mice. Large tumors were unaffected. This effect was dependent on the presence of CD8+ T cells and was associated with increased tumor-infiltrating lymphocytes. Because these activities are consistent with a mechanism that results in a decrease in the immunosuppressive environment of the tumor, we additionally examined the effect of COX-2 blockade combined with Ad.IFN-beta therapy, a treatment that we have previously demonstrated results in expansion of antitumor CD8+ CTLs and cures a high percentage of small mesothelioma tumors in mice. Ad.IFN-beta therapy combined with COX-2 inhibition was associated with an increased number of T cells within tumors and resulted in cures of small tumors, significant inhibition of the growth of large established tumors, and inhibition of the growth of metastatic tumor foci after surgical debulking. The additive effects of these modes of treatment suggests that it would be rational to combine COX-2 inhibition with immuno- and immunogene therapy approaches (perhaps in conjunction with surgical debulking) in human clinical trials of treatment of mesothelioma and other tumors.