Equine sarcoids

Sarcoids, the most common tumor of the horse, are fibroblastic, wart-like skin lesions that show variable manifestations. They are often invasive and recurrent, although they do not fulfill all criteria of malignancy. Due to their anatomic location, these tumors can sometimes cause loss of use of the horse. There is very strong evidence that sarcoids are caused by viruses closely related or identical to bovine papilloma viruses, and genetic studies have shown associations between genes in or near the equine major histocompatibility complex (MHC) and susceptibility to sarcoid. Several types of treatments have been successful in treating sarcoids, although the response to therapy is not consistent. Current treatment of sarcoids primarily involves antitumor therapy, but the development of preventative measures in the future may be directed against the causative papilloma virus. Sarcoid continues to be an important clinical entity for the equine practitioner.     

Generation of a systemic antitumor response with regional intratumoral injections of interferon gamma retroviral vector

The generation of a lasting systemic immune response is a primary goal for cancer immunotherapy. Here we examine the ability of high-titer IFN-gamma retroviral vector injected into an accessible tumor to generate significant antitumor responses at a distal untreated site. CT26 or B16F10 murine tumors were inoculated subcutaneously to form solid tumors in BALB/c or C57BL/6 mice. Seven to 10 days postinoculation, high-titer IFN-gamma retroviral vector was directly injected into the subcutaneous tumor nodule, and optimal dose and course of therapy were determined. As a model for disseminated disease, mice were inoculated intravenously with CT26 cells to form pulmonary lesions, at the same time as the subcutaneous injections. Regression of subcutaneous tumor correlated with a systemic response at the distal lung metastases in the IFN-gamma-treated group (p < 0.0005). Splenocytes from mice with completely regressed tumors had a twofold increase in percent specific cytotoxicity in a standard CTL assay as compared with nonresponding mice. CD8+ T cells were shown to be essential for the regional and systemic antitumor response, as determined by in vivo cell depletion experiments. These data demonstrate that IFN-gamma retroviral vector gene therapy delivered intralesionally can generate significant inhibition of pulmonary tumor formation distal to the treatment site. The data from these preclinical studies suggest the potential clinical value of retroviral vector-mediated cytokine gene therapy for systemic cancer.     

Current status of surgery for mediastinal tumors]

Impact of surgery on the result of mediastinal tumors is variable: In benign tumors such as teratoma, congenital cyst, intrathoracic struma and neurogenic tumor, a complete resection causes a good result. Simultaneous thoracotomy and laminectomy should be performed in the Dumbbell type of neurogenic tumor. Since complete resection of the invasive thymoma promises a good prognosis, excision of all the tumor and invading tissues followed by radiation therapy is recommended in the treatment of thymoma. In pure seminoma resection and radiation therapy is the treatment of choice, while in non-seminomatous germ cell tumor, aggressive chemo- and radiation therapy should be performed, until tumor markers such as AFP and HCG become negative. The operation is to be followed afterwards. A mass screening test for neuroblastoma in infant facilitates an early detection of this disease and promises a good result by chemotherapy, radiation therapy, and surgery. There is still a possibility that the result of treatment of the malignant mediastinal tumors would be improved by exact diagnosis and intensive treatment.     

Delayed vascular changes after antiangiogenic therapy with antivascular endothelial growth factor antibodies in human glioma xenografts in nude mice

OBJECTIVE: The purpose of this study was to examine the delayed effects of antivascular endothelial growth factor treatment on tumor growth and vascularity in a subcutaneous mouse tumor model of human glioblastoma. METHODS: Antivascular endothelial growth factor antibody treatment was administered for a period of 6 weeks, to suppress tumor growth. To detect late vascular effects, tumor vascular parameters for treated tumors and control tumors were analyzed 4 weeks thereafter. By that time, tumors had grown to adequate sizes (diameter, 8-10 mm) for comparison with untreated control tumors. Vascular parameters were quantified by using an image-analysis system. RESULTS: Vascular density was significantly lower in antivascular endothelial growth factor antibody-treated tumors, compared with control tumors of similar size. The vascular architecture of treated tumors was also distinctly different, compared with control tumors, showing larger but sparser vessel structures. CONCLUSION: These findings suggest that antiangiogenic therapy may have a prolonged effect on the vascular architecture of certain tumors, resulting in enduring changes in the tumor vessels. Because tumor vasculature plays an important role in the sensitivity to various treatment modalities, these changes are likely to influence the responses of these tumors to further therapy.     

A "distant" bystander effect of suicide gene therapy: regression of nontransduced tumors together with a distant transduced tumor

Antitumor gene therapy using herpes simplex type 1 thymidine kinase (TKh) and ganciclovir (GCV) treatment has revealed an important intratumoral bystander effect. A whole tumor can be eliminated when only a fraction of its tumor cells express TKh. We now report that the bystander effect not only acts within a tumor, but also between distant tumors. One TKh+ tumor was generated simultaneously with one or multiple TKh- tumors in different rat liver lobes such that there was no contact between the resulting tumors. Both the TKh+ and the TKh- tumors regressed after GCV treatment and showed infiltration with macrophages and T lymphocytes. This distant bystander effect, which is likely immune mediated, should be of major importance for gene therapy of disseminated tumors.     

Stimulation of tumors to synthesize tumor necrosis factor-alpha in situ using 5,6-dimethylxanthenone-4-acetic acid: a novel approach to cancer therapy

The selective induction of tumor vascular collapse represents an exciting approach to cancer treatment. However, clinical evaluation of tumor necrosis factor-alpha (TNF), an agent that accomplishes this goal, has been limited by systemic toxicity, and clinical approaches using bacterial components to induce TNF production have also been disappointing. Our laboratory has developed synthetic low molecular weight inducers of TNF, including 5,6-dimethylxanthenone-4-acetic acid (DMXAA), as an alternative strategy. DMXAA induces rapid vascular collapse in transplantable murine tumors and induces TNF synthesis in vitro in both murine and human systems. We show here that the extent of DMXAA-induced TNF synthesis is greater in tumors than that in the spleen, liver, or serum. As shown by in situ hybridization studies of the murine Colon 38 tumor, DMXAA induced tumor as well as host cells to express TNF mRNA. The distribution of cells containing TNF mRNA in tumor tissues after DMXAA administration contrasted significantly with that obtained after lipopolysaccharide (LPS) treatment, although splenic and hepatic tissues showed a similar distribution of TNF mRNA-positive cells. In the Colon 38 tumor, the action of LPS was limited to host cells in the periphery of the vessels. DMXAA treatment induced 7-fold higher peak TNF levels in tumor than in serum. In contrast, LPS treatment induced 9-fold higher TNF levels in serum than in tumor. DMXAA induced 35-fold higher TNF activity in the Colon 38 tissue than did LPS. One ovarian, one squamous, and three melanoma human tumor xenografts implanted in athymic nude mice expressed TNF mRNA of human and murine origin in response to DMXAA, confirming that DMXAA can activate both host and tumor cells. The use of low molecular weight agents to induce TNF synthesis in situ in the tumor represents a novel approach to TNF-mediated therapy of cancers.     

Bromocriptine therapy for "nonfunctioning" pituitary tumors

Bromocriptine therapy may cause regression of prolactinomas, but its effect on nonsecretory pituitary tumors is uncertain. Conventional treatment for such "functionless" tumors is surgery and/or radiotherapy, but recurrences pose a therapeutic dilemma. We describe a patient with such a tumor treated by surgery and radiotherapy who presented with recurrent disease 14 days later. On treatment with bromocriptine, 20 mg daily for 25 months, the intrasellar tumor recurrence had diminished in size and a suprasellar extension had almost disappeared. Bromocriptine therapy may therefore benefit some patients with nonsecretory pituitary tumors considered unsuitable for surgery or radiotherapy.     

Neoplasia of the male reproductive tract

Genital neoplasms in the male horse are relatively uncommon. Squamous cell carcinomas and squamous papillomas are the most commonly diagnosed neoplasms of the penis and prepuce. Geldings appear to be overrepresented for these types of neoplasms, and accumulation of smegma may be a contributing factor. Early diagnosis and treatment are essential for salvaging these organs before lesions become excessively large and invasive or are allowed to metastasize. Newer treatment modalities such as 5-fluorouracil appear to be promising alternatives to surgical excision. Although generally considered to be uncommon, testicular tumors may occur more frequently than previously thought and have the potential for devastating effects on stallion fertility. Cryptorchidism appears to play a role in the development of equine testicular tumors, especially teratomas. Seminoma is by far the most common testicular tumor of the mature stallion. Seminomas are rapidly growing tumors with a greater potential to metastasize in the horse than in other domestic species. Leydig cell and Sertoli cell tumors have been reported but are relatively rare in the stallion. Orchiectomy is the standard treatment for most testicular tumors. In certain circumstances, however, such as neoplasia occurring in the only functional testis, local cryotherapy of testicular tumors may prolong the breeding career of an affected stallion.     

Preoperative chemoradiation and pancreaticoduodenectomy for adenocarcinoma of the pancreas

The goal of multimodality therapy for localized pancreatic cancer is to maximize local-regional disease control and patient survival. In contrast to surgery for other solid tumors, prolonged recovery following pancreaticoduodenectomy may prevent the timely delivery of postoperative adjuvant therapy. Therefore, efforts at The University of Texas, M.D. Anderson Cancer Center have focused on the delivery of chemotherapy and radiation therapy prior to surgery in patients with localized pancreatic cancer. Clinical trials have emphasized the use of altered-fractionation schedules of radiation therapy combined with novel radiation-sensitizing agents. All treatment schemes aim to decrease toxicity and treatment time while improving therapeutic efficacy.     

Synergy between an antiangiogenic integrin alphav antagonist and an antibody-cytokine fusion protein eradicates spontaneous tumor metastases

The suppression and eradication of primary tumors and distant metastases is a major goal of alternative treatment strategies for cancer, such as inhibition of angiogenesis and targeted immunotherapy. We report here a synergy between two novel monotherapies directed against vascular and tumor compartments, respectively, a tumor vasculature-specific antiangiogenic integrin alphav antagonist and tumor-specific antibody-interleukin 2 (IL-2) fusion proteins. Simultaneous and sequential combination of these monotherapies effectively eradicated spontaneous liver metastases in a poorly immunogenic syngeneic model of neuroblastoma. This was in contrast to controls subjected to monotherapies with either an antiangiogenic integrin alphav antagonist or antibody-IL-2 fusion proteins, which were only partially effective at the dose levels applied. Furthermore, simultaneous treatments with the integrin alphav antagonist and tumor-specific antibody-IL-2 fusion proteins induced dramatic primary tumor regressions in three syngeneic murine tumor models, i.e., melanoma, colon carcinoma, and neuroblastoma. However, each agent used as monotherapy induced only a delay in tumor growth. A mechanism for this synergism was suggested because the antitumor response was accompanied by a simultaneous 50% reduction in tumor vessel density and a 5-fold increase in inflammatory cells in the tumor microenvironment. Subsequently, tumor necrosis was demonstrated only in animals receiving the combination therapy, but not when each agent was applied as monotherapy. The results suggest that these synergistic treatment modalities may provide a novel and effective tool for future therapies of metastatic cancer.     

Development of systemic immunologic responses against hepatic metastases during gene therapy for peritoneal carcinomatosis with retroviral HS-tk and ganciclovir

Gene therapy with retroviral mediated gene transfer of the herpes simplex thymidine kinase (HS-tk) gene into a tumor mass confers sensitivity of the tumor cells to ganciclovir (GCV). Tumor-specific immunologic responses may develop following treatment of the primary tumor with retroviral HS-tk and GCV. In the present study we assessed whether GCV treatment of HS-tk transduced colon cancer (TK+) implanted in the peritoneal cavity induced a systemic antitumor response that would inhibit growth of a second wild-type (TK-) tumor implanted in the liver. DHDK12 rat colon cancer cells were transduced in vitro with the retroviral HS-tk vector and established as a permanent cell line (TK+ cells). TK+ or TK- DHDK12 cells (6x10(6) cells) were injected intraperitoneally on day 0 into BD-IX rats. On day 10, TK- cells (3x10(6) cells) were injected into the liver in all the groups. The animals were then treated with GCV (150 mg/kg) for 13 days. TK+ peritoneal tumors underwent significant regression during therapy with GCV (0.05+/-0.004 g; n=7) compared to wild-type (TK-) tumors (2.2+/-0.7g; n=6) (P<0.05). The volume of TK- tumors in the liver was significantly lower in GCV-treated rats with TK+ peritoneal tumors (12.5+/-8.3 mm3) compared to rats with TK- peritoneal tumors (96.7+/-18.1 mm3) (P<0.05). Histology of the liver tumors in the TK+ groups showed a dense monocytic infiltrate with fibrosis and only occasional viable tumor cells. Gene therapy with retroviral HS-tk vectors may provide a novel approach to treatment of gastrointestinal cancer by both direct cytotoxicity and an indirect mechanism that may include enhanced immuno logic responses against disseminated disease.     

Radiosensitization and apoptosis

The toxicity of radiation to living tissues was discovered soon after the discovery of radioactivity itself and this toxicity is the basis for cancer therapy with radiation. Although this mode of therapy is often effective, its success is far from assured. One major difficulty in the implementation of radiotherapy is that normal tissues are also sensitive to killing by radiation so that treatment is often limited by the tolerance of normal tissues for radiation. Thus methods that sensitize tumor cells while sparing normal tissues could potentially lead to greater success with radiation as a therapy. Oncogenes are frequently altered in tumors, but are not in normal tissue making them potential targets for altering radiosensitivity and apoptosis in tumors.     

Enhanced tumor cell killing in the presence of ganciclovir by herpes simplex virus type 1 vector-directed coexpression of human tumor necrosis factor-alpha and herpes simplex virus thymidine kinase

Past studies have documented the promise of herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) suicide gene therapy as a potential antitumor treatment. HSV-TK converts the pro-drug ganciclovir (GCV) into a toxic nucleotide analogue, the incorporation of which into cellular DNA blocks cell proliferation. In this report, we have examined the hypothesis that the effectiveness of HSV-TK suicide gene therapy can be enhanced by coexpression of the antitumor cytokine human tumor necrosis factor-alpha (TNF-alpha) from the same replication-defective HSV-1 vector. In vitro testing demonstrated that TNF-alpha expression from this vector potentiated the killing of both TNF-alpha-sensitive L929 tumor cells and TNF-alpha-resistant U-87 MG cells in the presence of GCV. Furthermore, treatment of established intradermal L929 tumors in vivo with the TNF-alpha/TK vector and GCV resulted in prolonged animal survival compared with treatment with parental HSV-TK vector in the presence or absence of GCV. Treatment of intracerebral U-87 MG tumors showed a clear benefit of TK therapy, but a significant further increase in survival using the TNF-alpha vector could not be demonstrated. We found that potentiation of cell killing in vitro required intracellular TNF-alpha because purified protein added to the culture medium of cells infected with HSV-TK vector failed to have the same effect. Accordingly, potentiation in vivo should depend on efficient infection, but immunohistochemical analysis indicated that virus administration by U-87 MG intratumoral injection was inadequate, resulting in an estimated <1% infection of all tumor cells. Moreover, the majority of infected tumor cells were localized at the tumor margin. Together, these results suggest that TNF-enhanced tk gene therapy should provide a useful treatment for TNF-alpha-sensitive tumors and perhaps also for TNT-alpha-resistant tumors if vector delivery can be improved to increase the percentage of transduced tumor cells.     

Duration of cell cycle, onset of S phase and induced mitotic synchronisation in seeds of opium poppy, Papaver somniferum L

Primary brain tumors in two dogs were surgically removed followed by postoperative radiation therapy. The two tumors were confirmed histologically to be astrocytoma and meningioma, respectively. After the surgery, the neurological status of each dog improved dramatically and a total dose of 40 Gy was delivered to the surgical site to treat residual tumor tissue. Although the dog with astrocytoma died 6 months after surgery due to unknown causes, the dog with meningioma has lived for over 24 months with a degree of neurological disorder less severe than that before treatment. These results suggested the effectiveness of this type of therapy on brain tumor in dogs and therapeutic modality should be positively planned to treat canine brain tumors.     

Mammographic findings of recurrent breast cancer after lumpectomy and radiation therapy: comparison with the primary tumor

PURPOSE: To compare the mammographic findings of recurrent breast cancer with those of the primary tumor in patients who underwent lumpectomy and radiation therapy. MATERIALS AND METHODS: Mammograms were reviewed of primary and recurrent tumors in 25 patients (26 lesions). Mammographic appearance, location, and histopathologic characteristics were retrospectively compared between primary and recurrent tumors. RESULTS: Primary and recurrent tumors were mammographically similar in 21 (81%) of the 26 lesions. Of 14 primary tumors with calcifications, 12 (86%) recurred with calcifications, and of the 12 masses, nine (75%) recurred as masses. Recurrent tumors that occurred in the lumpectomy quadrant were more often similar in mammographic appearance to the primary tumor (20 of 22 tumors) than those in other quadrants (one of four tumors) (P < .02). CONCLUSION: After conservative treatment of breast cancer, the majority of recurrent tumors appear to be mammographically similar to primary tumors. It is prudent to review preoperative mammograms during follow-up of patients after lumpectomy and radiation therapy.     

Programmed cell death and radioresistance

Whereas apoptosis is a critical mode of cell deletion in normal organism development, apoptotic cells are also observed in tumors, especially following cytotoxic treatments, leading to questions about their role in tumor response to therapy. We have conducted a series of studies using murine tumor models and found that the ability of the tumor cells to undergo apoptosis correlates with tumor response to radiation. The best correlation was with the pretreatment apoptotic index, suggesting that apoptosis in some tumors may govern radiocurability by regulating the number of tumor clonogens. However, other roles for apoptosis in tumor response to radiation have not been ruled out. One of the important observations that has come from this work has been the heterogeneity in apoptosis propensity both within the cell population of a given tumor and among different types of tumors. Such findings underscore the fact that apoptosis is under complex genetic control and that some of the same oncogenes and tumor suppressor genes that are responsible for tumor initiation and progression to malignancy also dictate the apoptotic response to treatment. Understanding the biochemical and molecular pathways that govern this process may ultimately allow the development of strategies for modulating apoptosis for therapeutic benefit.     

Dendritic cells augment granulocyte-macrophage colony-stimulating factor (GM-CSF)/herpes simplex virus thymidine kinase-mediated gene therapy of lung cancer

Lung cancer, the leading cause of cancer death in the United States, is resistant to most currently available therapies. To evaluate a multicomponent gene therapy approach that replaces tumor-bearing host immune deficits, we genetically modified Line 1 (L1C2), a weakly immunogenic alveolar cell carcinoma cell line. L1C2 was transduced ex vivo with a retroviral construct that contained two components: a cytokine gene (granulocyte-macrophage colony-stimulating factor) and a drug sensitivity gene (herpes simplex virus thymidine kinase). The third component of this therapy, in vitro-activated syngeneic bone marrow-derived dendritic cells, was included to augment antigen presentation. The addition of ganciclovir (GCV) caused the lysis of transduced tumor cells, resulting in the release of potential tumor antigens. Ex vivo-transduced tumor cells regressed in vivo following GCV therapy but were not effective in the treatment of established parental tumors. To treat established tumors, dendritic cells were administered in combination with transduced tumor cells and GCV. A total of 50% of these mice rejected the 5-day-old established tumors and were immune to rechallenge with parental L1C2 cells. Thus, this multicomponent gene therapy system leads to both the regression of established tumors and enhanced immunogenicity in this weakly immunogenic murine lung cancer model.     

Molecular insights into cancer invasion: strategies for prevention and intervention

The diagnosis and treatment of solid tumors usually begins at a late stage when most patients already have occult or overt metastasis. Many years of cancer progression precede diagnosis of most solid tumors. Novel noncytotoxic therapeutics may be specially suited for administration during this interval. An important window of intervention can be defined as the period during which transition from a hyperproliferative state to acquisition of the capacity for invasion and metastasis occurs. Investigation of the molecular basis of invasion is uncovering strategies for delaying progression of preinvasive carcinoma and treatment of primary tumors and established metastasis. Although tumor cell invasion might not be rate limiting for the growth of metastasis, anti-invasive agents can block tumor angiogenesis and thereby indirectly block metastasis growth. Two classes of molecular anti-invasion targets exist: (a) cell surface and extracellular proteins, which mediate sensing, adhesion, and proteolysis; and (b) signal transduction pathways, which regulate invasion, angiogenesis, and proliferation. Both categories of targets yield treatment approaches that are now being tested in the clinic. Metalloproteinase inhibitors, such as BB94, are based on the recognition that metalloproteinases play a necessary role in invasion and angiogenesis. The orally active signal transduction inhibitor carboxyamidotriazole modulates non-voltage-gated calcium influx-regulated signal pathways and reversibly inhibits tumor invasion, growth, and angiogenesis. Blockade of invasion, angiogenesis, or cellular signal pathways is likely to generate a cytostatic, rather than a cytotoxic effect. Cytostatic therapy constitutes an alternative paradigm for clinical translation that may complement conventional cytotoxic therapy. For patients with newly diagnosed solid tumors, long-term cytostatic therapy could potentially create a state of metastasis dormancy or delay the time to overt relapse following cytotoxic agent-induced remission. Clinical toxicity and pharmacology using oral cytostatic agents in phase I trials and in adjuvant settings will provide an important foundation for the translation of this approach to the preinvasive carcinoma period.     

A gene therapy for cancer using intramuscular injection of plasmid DNA encoding interferon alpha

A cancer treatment is described in which i.m. injection of plasmid DNA (pDNA) encoding murine interferon alpha (mIFN-alpha) leads to potent antitumor effects on primary and metastatic tumors in mice. Mice bearing s.c. B16F10 melanoma, Cloudman melanoma, or glioma 261 tumors were injected i.m. with mIFN-alpha pDNA. In all three tumor models, a significant reduction in tumor volume and enhancement of survival was found after IFN pDNA therapy. The mIFN-alpha pDNA could be injected as infrequently as once every other week and still produce a significant antitumor effect, and, in a metastatic tumor model, the therapy markedly reduced the number of lung tumor metastases. Depletion of immune cell subsets indicated that CD8(+) T cells were required for the antitumor response. These studies demonstrate that primary and metastatic tumors can be treated systemically by i.m. injection of a plasmid encoding a cytokine gene.