Systemic administration of recombinant interferon alfa in carcinoma patients upregulates the expression of the carcinoma-associated antigens tumor-associated glycoprotein-72 and carcinoembryonic antigen

Radiopharmaceutical Switch Maintenance for Relapsed Ovarian Carcinoma

Switch maintenance, or using alternative therapeutic agents that were not administered during a prior course of cancer treatment, has emerged as an active clinical research and regulatory agency-approvable path in the National Cancer Institute (NCI) Cancer Therapy Evaluation Program (CTEP) drug-development sequence. To better inform the design of therapeutic radiopharmaceutical trials, we reviewed academic scholarship discussing the clinical use of maintenance approaches to cancer treatment. Women with advanced-stage primary platinum-refractory or platinum-resistant ovarian carcinoma and their courses of treatment provide context for our discussion. Twenty-four (10%) out of 244 trials for women with ovarian carcinoma fit our search terms for maintenance trials. Five (2%) trials studied radiopharmaceuticals as switch maintenance. In our opinion, radiopharmaceutical switch maintenance merits further testing in prospective trials for women with advanced-stage primary platinum recurrent or refractory ovarian carcinoma.

A recombinant scFv-FasLext as a targeting cytotoxic agent against human Jurkat-Ras cancer

Background

Targeted therapy of human cancers is an attractive approach and has been investigated with limited success. We have developed novel cytotoxic agents for targeted therapy of human cancers based on the extracellular cytotoxicity domain of CD178 (FasL) and the specificity offered by single chain antibodies (scFv) against dominant human tumor Ag TAG-72 (cc49scFv) and TAL6 (L6scFv).

Results

The cc49scFv-FasL_ext is highly effective in in vitro killing of human TAG-72⁺ Jurkat-Ras tumor cells with a 30,000 fold greater cytotoxicity as compared to soluble FasL (sFasL). On the other hand, L6scFv-FasL_ext only increased cytotoxicity 500-fold as compared with sFasL against TAL6⁺ HeLa cells in in vitro assays. The high specificity and strong cytotoxicity of cc49scFv-FasL_ext made it feasible to cure IP-implanted Jurkat-Ras tumors in SCID mice.

Conclusion

Our study demonstrated that scFv-FasL_ext with a strong cytotoxicity against sensitive human tumor targets may be useful as effective chemotherapeutic agents.

Interferons as potential adjuvants in prophylactic vaccines

IMPORTANCE OF THE FIELD

Vaccines are still one of the best approaches to manage infectious diseases. Despite the advances in drug therapies, prophylactic medicine is still more cost efficient and minimizes the burden in the heath system. Despite all the research in vaccine development, many infectious diseases are still without an effective vaccine. The use of adjuvants in vaccines has been one successful strategy to increase efficacy. IFNs are widely expressed cytokines that have potent antiviral effects. These cytokines are the first line of defense against viral infections and have important roles in immuno surveillance for malignant cells. One of the most promising uses of IFNs is as adjuvants that are co-applied with antigen in vaccines.

AREAS COVERED IN THIS REVIEW

In this review, a cumulative analysis of many of the studies that have used IFN-α, -β, -γ and -λ as adjuvants between 1987 and the present suggests that many do possess the capacity to serve as potent immunoadjuvants for vaccination.

WHAT THE READER WILL GAIN

This review provides a very large collection of studies involving all types of IFNs used as adjuvants in vaccines using different vaccination strategies and various animal models.

TAKE HOME MESSAGE

It is clear that the use of IFNs not only improved the efficacy and safety of most vaccines, but also had important immunomodulatory effect directing T(H)1 immune responses.

The antitumor and immunoadjuvant effects of IFN-alpha in combination with recombinant poxvirus vaccines

PURPOSE

IFN-alpha is a pleiotropic cytokine possessing immunomodulatory properties that may improve the efficacy of therapeutic cancer vaccines. The aim of this study was to evaluate the effectiveness and compatibility of combining recombinant IFN-alpha with poxvirus vaccines targeting the human carcinoembryonic antigen (CEA) in murine models of colorectal and pancreatic adenocarcinomas, where CEA is a self-antigen.

EXPERIMENTAL DESIGN

The phenotypic and functional effects of IFN-alpha were evaluated in the draining inguinal lymph nodes of tumor-free mice. We studied the effect of the site of IFN-alpha administration (local versus distal) on antigen-specific immune responses to poxvirus vaccination. Mechanistic studies were conducted to assess the efficacy of IFN-alpha and CEA-directed poxvirus vaccines in tumor-bearing CEA transgenic mice.

RESULTS

We identified a dose and schedule of IFN-alpha that induced a locoregional expansion of the draining inguinal lymph nodes and improved cellular cytotoxicity (natural killer and CD8(+)) and antigen presentation. Suppression of the vaccinia virus was avoided by administering IFN-alpha distal to the site of vaccination. The combination of IFN-alpha and vaccine inhibited tumor growth, improved survival, and elicited CEA-specific CTL responses in mice with CEA(+) adenocarcinomas. In mice with pancreatic tumors, IFN-alpha slowed tumor growth, induced CTL activity, and increased CD8(+) tumor-infiltrating lymphocytes.

CONCLUSIONS

These data suggest that IFN-alpha can be used as a biological response modifier with antigen-directed poxvirus vaccines to yield significant therapeutic antitumor immune responses. This study provides the rationale and mechanistic insights to support a clinical trial of this immunotherapeutic strategy in patients with CEA-expressing carcinomas.

Intracavitary radioimmunotherapy to treat solid tumors

Radioimmunotherapy (RIT) potentially is an attractive treatment for radiosensitive early-stage solid tumors and as an adjuvant to cytoreductive surgery. Topical administration of RIT may improve the efficacy because higher local concentrations are achieved. We reviewed the results of locally applied radiolabeled monoclonal antibodies for the treatment of solid tumors. Intracavitary RIT in patients with ovarian cancer and glioma showed improved targeting after local administration, as compared to the intravenous administration. In addition, various studies showed the feasibility of locally applied RIT in these patients. In studies that included patients with small-volume disease, adjuvant RIT in ovarian cancer and glioma showed to be at least as effective as standard therapy. The information about RIT for peritoneal carcinomatosis of colorectal origin is scarce, while results from preclinical data are promising. RIT may be applied for other, relatively unexplored indications. Studies on the application of radiolabeled antibodies in early urothelial cell cancer have been performed, showing that intracavitary RIT may hold a promise. Moreover, in patients with malignant pleural mesothelioma or malignant pleural effusion, RIT may play a role in the palliative treatment. Intracavitary RIT limits toxicity and improves tumor targeting. RIT is more effective in patients with small-volume disease of solid cancers. RIT may have potential for palliation in patients with malignant pleural mesothelioma or malignant pleural effusion. The future of RIT may, therefore, not only be in the inclusion in contemporary multimodality treatment, but also in the expansion to palliative treatment.

Current immunotherapeutic strategies in breast cancer

Despite significant advances in the administration of combination cytotoxic chemotherapy, the overall 5-year survival rate is about 75% for a woman who has node-positive breast cancer, and metastatic disease is considered incurable. Recent advances in our understanding of the immune system have led to the hope that manipulation of this organ system could be used as a cancer treatment. Strategies that have been used in the immune therapy of breast cancer include the administration of exogenous cytokines, vaccines, and humanized monoclonal antibodies (mAb). Each of these approaches is discussed in turn in this article.

Operative probe scintimetry with indium and technetium for colorectal cancer

Surgeons introduced the hand-held gamma detection probe in combination with tumor-directed monoclonal antibodies in patients with colorectal cancer. The clinicians conducted innovative research involving antibody chemistry and variation as well as radioactive dosimetry and decay. The results of these studies represented an era when surgeons began reporting on specific lesion detection and the impact of the antibody administration on the management of the patient. The summary of the important early trials involving monoclonal antibodies and probe scintimetry provides a valuable look into the early development of the antibody technology and a glimpse of potential future applications using the gamma detection probe.

Presurgical therapy in metastatic renal cell carcinoma

The standard approach for managing patients with metastatic renal cell carcinoma consists of a cytoreductive nephrectomy followed by immunotherapy, chemotherapy or a targeted agent. Optimal timing of surgery and systemic therapy is not known, and has not been researched. A number of questions arise. First, in the era of antivascular therapy, is cytoreductive nephrectomy a necessity? Second, is it possible that pretreatment with systemic therapy prior to cytoreductive nephrectomy improves surgical outcome and survival? Third, which agents are best suited for an integration of surgery with systemic therapy, both in the metastatic and the nonmetastatic setting? This review will address each of these questions and summarize ongoing trials that are designed to provide some of the answers.

Phase I study of 90Y-CC49 monoclonal antibody therapy in patients with advanced non-small cell lung cancer: effect of chelating agents and paclitaxel co-administration

PURPOSE

This trial was designed to evaluate strategies to improve the efficacy of a radiolabeled monoclonal antibody (mCC49) against tumor-associated glycoprotein-72 (TAG-72) in patients with non-small cell lung cancer (NSCLC). The aims of this study were to determine: safety and maximum tolerated dose (MTD) of (90)Y-mCC49 in combination with interferon alpha2beta (IFN); whether calcium disodium versonate (EDTA) or diethylenetriamine penta-acetic acid (DTPA) could reduce myelosuppression; and safety and MTD of paclitaxel (Taxol) in combination with (90)Y-mCC49.

EXPERIMENTAL DESIGN

Patients with advanced (TAG-72 positive) non-small cell lung cancer were entered in three phases; the first was the dose escalation of a single agent (90)Y-mCC49. In the second phase, the dose escalation of (90)Y-mCC49 was attempted with concurrent EDTA or DTPA chelator therapy. In the third phase, radiosensitization with a continuous infusion of paclitaxel (96-hour) was administered with (90)Y-mCC49. All patients received IFN for TAG-72 up-regulation.

RESULTS

Thirty-four patients were evaluable. Reversible Grade 4 neutropenia and thrombocytopenia were the dose-limiting toxicities (DLTs). The MTD of (90)Y-mCC49/IFN was 14 mCi/m(2). EDTA did not alter toxicity, while there was a modest reduction of myelosuppression with DTPA. The MTD of continuous infusion paclitaxel in combination with 14 mCi/m(2) of (90)Y-CC49 was 60 mg/m(2). There were no objective tumor responses.

CONCLUSIONS

(90)Y-mCC49/IFN was well tolerated at a dose of 14 mCi/m(2). The clinical effect of adjunctive chelating therapy with DTPA was modest. The MTD of coadministered continuous infusion (96-hour) paclitaxel was 60 mg/m(2). Because of the immunogenicity of the murine compound, future studies are planned using a humanized version of CC49.

Review: Milstein Award lecture: interferons and cancer: where from here?

Interferons (IFNs) remain the most broadly active cytokines for cancer treatment, yet ones for which the full potential is not reached. IFNs have impacted positively on both quality and quantity of life for hundreds of thousands of cancer patients with chronic leukemia, lymphoma, bladder carcinoma, melanoma, and renal carcinoma. The role of the IFN system in malignant pathogenesis continues to enhance understanding of how the IFN system may be modulated for therapeutic advantage. Reaching the full potential of IFNs as therapeutics for cancer will also result from additional understanding of the genes underlying apoptosis induction, angiogenesis inhibition, and influence on immunologic function. Food and Drug Administration (FDA) approval of IFNs occurred less than 20 years ago; after 40 years, third-generation products of early cytotoxics, such as 5- fluorouracil (5FU), are beginning to reach clinical approval. Thus, substantial potential exists for additional application of IFNs and IFN inducers as anticancer therapeutics, particularly when one considers that their pleiotropic cellular and molecular effects have yet to be fully defined.

A novel monoclonal antibody design for radioimmunotherapy

The generation of chimeric and complementary-determining region (CDR) grafted monoclonal antibodies (MAb) have reduced the immunogenicity problem in the clinical application of radioimmunotherapy with monoclonal antibodies. However, humanization (Hu) has prolonged the circulation (plasma T1/2) of radiolabeled antibodies, resulting in an increased normal tissue exposure to radioactivity and greater dose-limiting bone marrow suppression. To overcome this problem, a tumor-associated glycoprotein (TAG)-72-specific CDR grafted MAb with C(H)2 domain deletion (DeltaC(H)2) was developed from the MAb CC49. Preclinical studies have demonstrated that HuCC49 DeltaC(H)2 clears more rapidly from the plasma of mice than HuCC49. This preliminary report describes the initial human experience with HuCC49 DeltaC(H)2 radiolabeled with 131I and administered to patients with metastatic colorectal carcinoma. In this pilot study we enrolled four patients who received a single infusion of 20 mg of HuCC49 DeltaC(H)2 (total protein dose) labeled with 10 mCi of 131I. Pharmacokinetics, biodistribution, dosimetry, and immune response were evaluated over 2-6 weeks. No toxicity was observed in this group of patients. A one-compartment bolus model using the non-linear (NLIN) procedures in Statistical Analysis Software (SAS; SAS, Incorporated, Cary, NC) best describes the pharmacokinetics of the 131I-HuCC49 DeltaC(H)2 with a plasma mean T1/2 of 20 +/- 3 hours, a mean residence time (MRT) of 29 +/- 4 hours and a clearance rate (Cl) of 1.5 +/- 0.1 mL/hours/kg. The whole body and marrow radiation dose estimates were 0.55 +/- 0.06 rad/mCi and 1.00 +/- 0.14 rad/mCi, respectively. All patients had positive localization of antibody to metastatic tumor sites. The 131I-HuCC49 DeltaC(H)2 biodistribution was similar to murine CC49. Three patients had no evidence of antibody response to HuCC49 DeltaC(H)2 over 6 weeks of observation, and one patient had a marginal response by week 6. Intravenous administration of HuCC49 DeltaC(H)2 is safe and well tolerated. The deleted C(H)2 construct has a shorter half-life compared with prior studies of murine CC49 but with similar biodistribution and low immunogenicity. These studies support the further clinical investigation of this agent in phase I trials by intravenous and intraperitoneal routes.

Imaging and therapy of tumors induced to express somatostatin receptor by gene transfer using radiolabeled peptides and single chain antibody constructs

The fields of radioimmunodetection and radioimmunotherapy began with an initial paradigm that a targeting molecule (eg, antibody) carrying a radioisotope had the potential of selectively imaging and delivering a therapeutic dose of radiation to tumor sites. A second paradigm was developed in which injection of the targeting molecule was separated from injection of a short-lived radioisotope-labeled ligand (so-called "pretargeting strategy"). This strategy has improved radioisotope delivery to tumors in animal models, enhanced radioimmune imaging in man, and therapeutic trials are in an early phase. We proposed a third paradigm to achieve radioisotopic localization at tumor sites by inducing tumor cells to synthesize a membrane expressed receptor with a high affinity for infused radiolabeled ligands. The use of gene transfer technology to induce expression of high affinity membrane receptors can enhance the specificity of radioligand localization, while the use of radioisotopes with the ability to deliver radiation damage across several cell diameters will compensate for less than perfect transduction efficiency. This approach was termed "Genetic Radioisotope Targeting Strategy." Using this strategy, induction of high levels of gastrin releasing peptide receptor or human somatostatin receptor subtype 2 expression and selective tumor uptake of radiolabeled peptides was achieved. The advantages of the genetic transduction approach are (1) constitutive expression of a tumor-associated antigen/receptor is not required; (2) tumor cells are altered to express a new target receptor or increased quantities of an existing receptor at levels that may significantly improve tumor targeting of radiolabeled ligands compared with normal tissues; (3) gene transfer can be achieved by intratumoral or regional injection of gene vectors; (4) it is feasible to target adenovirus vectors to receptors overexpressed on tumor cells by modifying adenoviral tropism (binding) so that the virus will be targeted specifically to the desired tumor; and (5) it is possible to coexpress the receptor gene and a therapeutic gene, such as cytosine deaminase, for molecular prodrug therapy to produce an enhanced therapeutic effect.

Thymosin alpha(1) in combination with cytokines and chemotherapy for the treatment of cancer

Multiple therapeutic approaches have been tested in different experimental tumour models and in human cancers. Most part of them are based on the hypothesis that the inhibition of tumour growth requires a strong immune response in which a main role is played by CTLs. It is known, however, that an efficient CTL response requires expression of tumour antigens, MHC class I surface molecules presentation, expression of different co-stimulatory molecules and a sustained generation and proliferation of specific cytotoxic CD8+ cells with an efficient CD4+ cooperation. In this context, our group has extensively explored a protocol of combined therapy consisting of the use of chemotherapeutic agents associated with thymosin alpha 1 (Talpha 1) and different cytokines, whose efficacy has been demonstrated in experimental models as well as in human cancers. In this manuscript, the main data supporting a pivotal role of Talpha 1 in such combination protocols are reviewed. In particular, a special mention of the molecular mechanisms underlying the effects of Talpha 1 on immune effector cells as well as on target tumour cells is provided. These data contribute to explain the mechanism of action of Talpha 1, when used in combination therapy, for the treatment of cancer and provide new insights in predicting further possible applications of this peptide in other pathological conditions.

Interferons Can Upregulate the Expression of the Tumor Associated Antigen G250-MN/CA IX, a Potential Target for (Radio)Immunotherapy of Renal Cell Carcinoma

BACKGROUND

Interleukin-2 (IL-2) and interferon-alpha (IFN-alpha) can induce therapeutic responses in a minority (5-25%) of patients with metastatic renal cell carcinoma (RCC). G250-MN/CA IX, a tumor-associated antigen expressed on the majority of clear cell RCCs, is a potential (radio)immunotherapeutic target for G250-antibody based (radio)immunotherapy. We investigated the effect of the biological response modifiers (BRMs) IL-2, IFN-alpha, and IFN-gamma on the expression of the G250 antigen on RCC cells.

METHODS

In vitro, the expression of the G250 antigen was measured by flow cytometry (FCM) after culturing RCC cells in the presence of various concentrations of the BRMs. Additionally, the number of G250 epitopes per cell was determined quantitatively by Scatchard analysis.

RESULTS

Upregulation of G250 expression was observed on RCC cells cultured in the presence of IFN-alpha or IFN-gamma, whereas the addition of IL-2 had no effect. For both IFNs a clear dose-response relation between G250 antigen expression and IFN dose was observed, with IFN-gamma being the more potent agent. G250 expression could be upregulated four-fold. Interestingly, the effect of combining IFN-alpha and IFN-gamma revealed a more pronounced upregulation of G250 expression than either one of the IFNs alone.

CONCLUSIONS

On the basis of in vitro experiments, G250 expression can be upregulated by IFN-alpha and IFN-gamma. In vivo studies are warranted to investigate whether due to IFN treatment increased G250 expression occurs, and whether increased G250 expression can enhance the therapeutic efficacy of G250-antibody based (radio)immunotherapy.

Intraperitoneal radioimmunochemotherapy of ovarian cancer: a phase I study

A phase I trial was designed to examine the feasibility of combining interferon and Taxol with intraperitoneal radioimmunotherapy (177Lu-CC49). Patients with recurrent or persistent ovarian cancer confined to the abdominal cavity after first line therapy, Karnofsky performance status > 60, adequate liver, renal and hematologic function, and tumor that reacted with CC49 antibody were enrolled. Human recombinant alpha interferon (IFN) was administered as 4 subcutaneous injections of 3 x 10(6) U on alternate days beginning 5 days before RIT to increase the expression of the tumor-associated antigen, TAG-72. The addition of IFN increased hematologic toxicity such that the maximum tolerated dose (MTD) of the combination was 40 mCi/m2 compared to 177Lu-CC49 alone (45 mCi/m2). Taxol, which has radiosensitizing effects as well as antitumor activity against ovarian cancer, was given intraperitoneally (i.p.) 48 hrs before RIT. It was initiated at 25 mg/m2 and escalated at 25 mg/m2 increments to 100 mg/m2. Subsequent groups of patients were treated with IFN + 100 mg/m2 Taxol + escalating doses of 177Lu-CC49. Three or more patients were treated in each dose group and 34 patients were treated with the 3-agent combination. Therapy was well tolerated with the expected reversible hematologic toxicity. The MTD for 177Lu-CC49 was 40 mCi/m2 when given with IFN + 100 mg/m2 Taxol. Interferon increased the effective whole body half-time of radioactivity and the whole body radiation dose. Taxol did not have a significant effect on pharmacokinetic or dosimetry parameters. Four of 17 patients with CT measurable disease had a partial response (PR) and 4 of 27 patients with non-measurable disease have progression-free intervals of 18+, 21+, 21+, and 37+ months. The combination of intraperitoneal Taxol chemotherapy (100 mg/m2) with RIT using 177Lu-CC49 and interferon was well tolerated, with bone marrow suppression as the dose-limiting toxicity.

Noninvasive localization of tumors by immunofluorescence imaging using a single chain Fv fragment of a human monoclonal antibody with broad cancer specificity

BACKGROUND

A single chain antibody fragment, NovoMAb-G2-scFv, derived from a human anti-tumor monoclonal antibody recognizes tumor antigen molecules expressed on a wide variety of human cancers including melanoma, breast carcinoma, colon adenocarcinoma, squamous cell carcinoma, lung carcinoma, and prostate carcinoma. This study was designed to evaluate the use of a NovoMab-G2-scFv/cyanine fluorochrome (Cy5.5.18) conjugate as diagnostic tool for in vivo imaging of tumors.

METHODS

The NovoMab-G2-scFv-Cy5 complex was administered to athymic mice injected subcutaneously with human melanoma tumor cells, and the distribution of fluorescence was imaged noninvasively using a charge-coupled device camera. Images were acquired 2, 6, 12, 24, 48, and 72 hours after injection.

RESULTS

Fluorescence was detected at the tumor site after injection of NovoMab-G2-scFv-Cy5 but not after injection of a labeled irrelevant control antibody fragment. Fluorescence from the tumor site peaked 2 hours after injection and gradually declined, reaching a minimum 72 hours after injection. Fluorescence was also apparent in the kidneys, indicating clearance of the complex through the kidneys. Results suggest that 16% and 73% of the antibody is located in the tumor and kidneys, respectively. Imaging of isolated organs confirmed the presence of the NovoMab-G2-scFv-Cy5 complex in tumors, kidneys, and liver. No fluorescence was observed in other organs.

CONCLUSIONS

Specific binding of the antibody-dye complex to the tumor was observed, and the kinetics of binding to tumors and kidneys were determined. These results suggest that the NovoMab-G2-scFv-Cy5.5 complex may be used for noninvasive tumor localization.

Experimental radioimmunotherapy

Experimental radioimmunotherapy (RIT) studies in animal models have contributed significantly to the design of clinical RIT protocols, although the results have not always been directly translated. Reviewed in this article are current areas of active research in experimental RIT to increase the therapeutic ratio that are likely to have a significant impact on the design of future clinical studies. Approaches for increasing the therapeutic efficacy of RIT include the development of new targeting molecules (genetically engineered monoclonal antibodies, antibody fragments, single-chain antibodies, diabodies and minibodies, fusion toxins, or peptides); improved labeling chemistry; novel radionuclide use and fractionation; locoregional administration; pretargeting; use of biological response modifiers or gene transfer techniques to increase target receptor expression; bone marrow transplantation; and combined modality therapy with external-beam radiation therapy, chemotherapy, or gene therapy. Further research with these new experimental approaches in preclinical animal models is necessary to contribute to advances in the treatment of cancer patients using radiolabeled antibodies and peptides.

Radioimmunodiagnosis and therapy

Although promising results with radioimmunotherapy and radioimmunodiagnosis in haematological diseases, have been reported, they are less encouraging results in solid tumours. Experimental mathematical models suggest that optimization of antibody-based therapy and diagnosis is possible and that further research towards improvement is warranted. In this review, the major problems of radioimmunotherapy and diagnosis are discussed. Particular items adressed include tumour uptake of antibodies and antibody-fragments, the target/non-target ratio, immunogenicity and the selection of radionuclides.

In vitro upregulation of carcinoembryonic antigen expression by combinations of cytokines

Interferons are able to enhance the expression of carcinoembryonic antigen (CEA) on tumour cells, allowing improved tumour targeting. In this report the hypothesis is tested that combinations of cytokines may further increase the tumour antigen expression. The combination of both IFN-gamma and IFN-alpha with interleukin-6 demonstrated a significant additive effect on the CEA-expression. This was found by quantitatively analysing the CEA-expression on human colorectal tumour cells by flow cytometry. It is concluded that combinations of cytokines show the potential of inducing tumour antigen expression for improved tumour targeting.

In vivo imaging of tumors with protease-activated near-infrared fluorescent probes

We have developed a method to image tumor-associated lysosomal protease activity in a xenograft mouse model in vivo using autoquenched near-infrared fluorescence (NIRF) probes. NIRF probes were bound to a long circulating graft copolymer consisting of poly-L-lysine and methoxypolyethylene glycol succinate. Following intravenous injection, the NIRF probe carrier accumulated in solid tumors due to its long circulation time and leakage through tumor neovasculature. Intratumoral NIRF signal was generated by lysosomal proteases in tumor cells that cleave the macromolecule, thereby releasing previously quenched fluorochrome. In vivo imaging showed a 12-fold increase in NIRF signal, allowing the detection of tumors with submillimeter-sized diameters. This strategy can be used to detect such early stage tumors in vivo and to probe for specific enzyme activity.

Novel clinical approaches in monoclonal antibody-based management in colorectal cancer patients: radioimmunoguided surgery and antigen augmentation

Surgery, the most effective treatment for colon and rectal cancer, is based on empirical knowledge of the patterns of tumor spread, gross findings at laparotomy, and histologic confirmation of tumor-free margins. In spite of the many technical improvements in surgery, there has not been a significant change in cure rates for colon and rectal cancers. In fact, one-half of affected patients will not survive 5 years. It is in this arena of treatment for primary colon and rectal cancer patients that radioimmunoguided surgery (RIGS) technology may provide the most benefit. RIGS is an intraoperative procedure for detection of carcinoma lesions that are targeted with a radiolabeled monoclonal antibody (MAb) to provide the surgeon with immediate intraoperative definition of tumor margins and identification of occult disease. To optimize this technique, our studies were designed to increase tumor uptake by higher affinity CC-49 (a second-generation MAb) and to increase tumor antigen expression using biological response modifiers (BRMs). The ability of BRMs, such as interferons (IFNs), to enhance the expression of tumor-associated antigens, may play an important role in an adjuvant setting for MAb-based treatment. Preclinical and clinical data provided evidence for the use of IFN as an adjuvant to enhance MAb-targeting of human carcinoma lesions. A combination protocol with IFN and RIGS is ongoing at our institution.

Identification of a human CD8+ T lymphocyte neo-epitope created by a ras codon 12 mutation which is restricted by the HLA-A2 allele

Point mutations in the ras proto-oncogenes, notably at codon 12, are found in high frequency of human malignancies and, thus, may be appropriate targets for the induction of tumor-specific T cell responses in cancer immunotherapy. In this study, we examined the mutant ras protein sequence reflecting the substitution of Gly to Val at position 12 as a putative point-mutated determinant for potential induction of an HLA-A2-reactive, CD8+ cytotoxic T lymphocyte (CTL) response. We identified the ras 4-12(Val12) sequence as a minimal 9-mer peptide, which displayed specific binding to HLA-A2 by T2 bioassays. Peptide binding to HLA-A2 on T2 cells was weak and required coincubation with exogenous beta(2)-microglobulin to facilitate and enhance complex formation. In contrast, the wild-type ras 4-12(Gly12) peptide failed to bind to HLA-A2 even in the presence of beta(2)-microglobulin, consistent with the hypothesis that the point mutation creates a C-terminus anchor residue. A CD8+ CTL line against the ras 4-12(Val12) peptide was derived in vitro from a normal HLA-A2+ donor using a model culture system consisting of T2 cells as antigen presenting cells pulsed with exogenous mutant ras peptide and beta(2)-microglobulin plus cytokines (interleukin-2 and 12). Functional characterization of CD8+ CTL line revealed (1) peptide-specific and HLA-A2-restricted cytotoxicity against a panel of peptide-pulsed targets; (2) no specific lysis using the normal ras peptide sequence; (3) half-maximal lysis with exogenous peptide of approximately 0.3 microM; (4) lysis of HLA-A2+ B cell lines infected with a recombinant vaccinia virus construct encoding the point-mutated human K-ras gene; and (5) specific lysis of the HLA-A2+ SW480 colon carcinoma cell line expressing the naturally occurring K-ras Val12 mutation. Maximal lysis of SW480 cells occurred following interferon (IFN)-gamma pretreatment, which correlated with enhanced HLA-A2 and ICAM-1 (CD54) expression. Specificity of lysis was revealed by the absence of lysis against a HLA-A2+ melanoma cell line (+/- IFN-gamma), which lacked the mutant Val12 mutation, and the inability of an irrelevant CD8+ CTL line to lyse SW480 (+/- IFN-gamma) unless the appropriate exogenous peptide was added. These findings demonstrated that tumor cells may endogenously process and express mutant ras epitopes, such as the 4-12(Val12) sequence, albeit in limiting amounts that may be potentiated by IFN-gamma treatment. These data support the biological relevance of this sequence and, thus, may have important implications for the generation of ras oncogene-specific CTL responses in clinical situations.