Combined gemcitabine and radioimmunotherapy for the treatment of pancreatic cancer

MUC1-Targeted Radiopharmaceuticals in Cancer Imaging and Therapy

Mucin 1 (MUC1) is a large, transmembrane mucin glycoprotein overexpressed in most adenocarcinomas and plays an important role in tumor progression. Regarding its cellular distribution, biochemical features, and function, tumor-related MUC1 varies from the MUC1 expressed in normal cells. Therefore, targeting MUC1 for cancer immunotherapy and imaging can exploit the difference between cancerous and normal cells. Radiopharmaceuticals have a potential use as carriers for the delivery of radionuclides to tumors for a diagnostic imaging and radiotherapy. Several radiolabeled targeting molecules like peptides, antibodies, and aptamers have been efficiently demonstrated in detecting and treating cancer by targeting MUC1. This review provides a brief overview of the current status of developments and applications of MUC1-targeted radiopharmaceuticals in cancer imaging and therapy.

Mucins in pancreatic cancer: A well-established but promising family for diagnosis, prognosis and therapy

Mucins are a family of multifunctional glycoproteins that mostly line the surface of epithelial cells in the gastrointestinal tract and exert pivotal roles in gut lubrication and protection. Pancreatic cancer is a lethal disease with poor early diagnosis, limited therapeutic effects, and high numbers of cancer‐related deaths. In this review, we introduce the expression profiles of mucins in the normal pancreas, pancreatic precursor neoplasia and pancreatic cancer. Mucins in the pancreas contribute to biological processes such as the protection, lubrication and moisturization of epithelial tissues. They also participate in the carcinogenesis of pancreatic cancer and are used as diagnostic biomarkers and therapeutic targets. Herein, we discuss the important roles of mucins that lead to the lethality of pancreatic adenocarcinoma, particularly MUC1, MUC4, MUC5AC and MUC16 in disease progression, and present a comprehensive analysis of the clinical application of mucins and their promising roles in cancer treatment to gain a better understanding of the role of mucins in pancreatic cancer.

Radioimmunotherapy of Pancreatic Ductal Adenocarcinoma: A Review of the Current Status of Literature

Pancreatic ductal adenocarcinoma (PDAC) has long been associated with low survival rates. A lack of accurate diagnostic tests and limited treatment options contribute to the poor prognosis of PDAC. Radioimmunotherapy using α- or β-emitting radionuclides has been identified as a potential treatment for PDAC. By harnessing the cytotoxicity of α or β particles, radioimmunotherapy may overcome the anatomic and physiological factors which traditionally make PDAC resistant to most conventional treatments. Appropriate selection of target receptors and the development of selective and cytotoxic radioimmunoconjugates are needed to achieve the desired results of radioimmunotherapy. The aim of this review is to examine the growing preclinical and clinical trial evidence regarding the application of α and β radioimmunotherapy for the treatment of PDAC. A systematic search of MEDLINE® and Scopus databases was performed to identify 34 relevant studies conducted on α or β radioimmunotherapy of PDAC. Preclinical results demonstrated α and β radioimmunotherapy provided effective tumour control. Clinical studies were limited to investigating β radioimmunotherapy only. Phase I and II trials observed disease control rates of 11.2%-57.9%, with synergistic effects noted for combination therapies. Further developments and optimisation of treatment regimens are needed to improve the clinical relevance of α and β radioimmunotherapy in PDAC.

Cancer-associated mucins: role in immune modulation and metastasis

Mucins (MUC) protect epithelial barriers from environmental insult to maintain homeostasis. However, their aberrant overexpression and glycosylation in various malignancies facilitate oncogenic events from inception to metastasis. Mucin-associated sialyl-Tn (sTn) antigens bind to various receptors present on the dendritic cells (DCs), macrophages, and natural killer (NK) cells, resulting in overall immunosuppression by either receptor masking or inhibition of cytolytic activity. MUC1-mediated interaction of tumor cells with innate immune cells hampers cross-presentation of processed antigens on MHC class I molecules. MUC1 and MUC16 bind siglecs and mask Toll-like receptors (TLRs), respectively, on DCs promoting an immature DC phenotype that in turn reduces T cell effector functions. Mucins, such as MUC1, MUC2, MUC4, and MUC16, interact with or form aggregates with neutrophils, macrophages, and platelets, conferring protection to cancer cells during hematological dissemination and facilitate their spread and colonization to the metastatic sites. On the contrary, poor glycosylation of MUC1 and MUC4 at the tandem repeat region (TR) generates cancer-specific immunodominant epitopes. The presence of MUC16 neo-antigen-specific T cell clones and anti-MUC1 antibodies in cancer patients suggests that mucins can serve as potential targets for developing cancer therapeutics. The present review summarizes the molecular events involved in mucin-mediated immunomodulation, and metastasis, as well as the utility of mucins as targets for cancer immunotherapy and radioimmunotherapy.

Novel agents for advanced pancreatic cancer

Pancreatic cancer is relatively insensitive to conventional chemotherapy. Therefore, novel agents targeting dysregulated pathways (MAPK/ERK, EGFR, TGF-β, HEDGEHOG, NOTCH, IGF, PARP, PI3K/AKT, RAS, and Src) are being explored in clinical trials as monotherapy or in combination with cytotoxic chemotherapy. This review summarizes the most recent advances with the targeted therapies in the treatment of patients with advanced pancreatic cancer.

(90)Y-clivatuzumab tetraxetan with or without low-dose gemcitabine: A phase Ib study in patients with metastatic pancreatic cancer after two or more prior therapies

BACKGROUND

For patients with metastatic pancreatic adenocarcinoma, there are no approved or established treatments beyond the 2nd line. A Phase Ib study of fractionated radioimmunotherapy was undertaken in this setting, administering (90)Y-clivatuzumab tetraxetan (yttrium-90-radiolabelled humanised antibody targeting pancreatic adenocarcinoma mucin) with or without low radiosensitising doses of gemcitabine.

METHODS

Fifty-eight patients with three (2-7) median prior treatments were treated on Arm A (N=29, (90)Y-clivatuzumab tetraxetan, weekly 6.5 mCi/m(2)doses×3, plus gemcitabine, weekly 200 mg/m(2) doses×4 starting 1 week earlier) or Arm B (N=29, (90)Y-clivatuzumab tetraxetan alone, weekly 6.5 mCi/m(2)doses×3), repeating cycles after 4-week delays. Safety was the primary endpoint; efficacy was also evaluated.

RESULTS

Cytopaenias (predominantly transient thrombocytopenia) were the only significant toxicities. Fifty-three patients (27 Arm A, 26 Arm B, 91% overall) completed ⩾1 full treatment cycles, with 23 (12 Arm A, 11 Arm B; 40%) receiving multiple cycles, including seven (6 Arm A, 1 Arm B; 12%) given 3-9 cycles. Two patients in Arm A had partial responses by RECIST criteria. Kaplan-Meier overall survival (OS) appeared improved in Arm A versus B (hazard ratio [HR] 0.55, 95% CI: 0.29-0.86; P=0.017, log-rank) and the median OS for Arm A versus Arm B increased to 7.9 versus 3.4 months with multiple cycles (HR 0.32, P=0.004), including three patients in Arm A surviving >1 year.

CONCLUSIONS

Clinical studies of (90)Y-clivatuzumab tetraxetan combined with low-dose gemcitabine appear feasible in metastatic pancreatic cancer patients beyond 2nd line and a Phase III trial of this combination is now underway in this setting.

The role of PAM4 in the management of pancreatic cancer: diagnosis, radioimmunodetection, and radioimmunotherapy

PAM4, a new monoclonal antibody (MAb) known as clivatuzumab, is highly reactive with pancreatic cancer and precursor lesions. It is absent from the normal tissues and has limited reactivity with nonpancreatic cancer. The detailed characteristic of the PAM4 epitope is unknown but recent studies have shown that it is dependent on MUC1 glycosylation status. The limited PAM4 expression pattern makes it an attractive candidate for management of pancreatic adenocarcinoma. In addition, PAM4 is a serum biomarker for diagnosis of pancreatic cancer. Several different radiolabeled immunodiagnostic and immunotherapeutic agents of PAM4 have been developed and some are being evaluated in preclinical and/or clinical studies. The review will focus on PAM4 and its potential utility for the diagnosis, radioimmunodetection, and radioimmunotherapy of pancreatic cancer.

General overview of radioimmunotherapy of solid tumors

Radioimmunotherapy (RIT) represents an attractive tool for the treatment of local and/or diffuse tumors with radiation. In RIT, cytotoxic radionuclides are delivered by monoclonal antibodies that specifically target tumor-associated antigens or the tumor microenvironment. While RIT has been successfully employed for the treatment of lymphoma, mostly with radiolabeled antibodies against CD20 (Bexxar(®); Corixa Corp., WA, USA and Zevalin(®); Biogen Idec Inc., CA, USA and Schering AG, Berlin, Germany), its use in solid tumors is more challenging and, so far, few trials have progressed beyond Phase II. This review provides an update on antibody-radionuclide conjugates and their use in RIT. It also discusses possible optimization strategies to improve the clinical response by considering biological, radiobiological and physical features.

Effects of a non thermal plasma treatment alone or in combination with gemcitabine in a MIA PaCa2-luc orthotopic pancreatic carcinoma model

Pancreatic tumors are the gastrointestinal cancer with the worst prognosis in humans and with a survival rate of 5% at 5 years. Nowadays, no chemotherapy has demonstrated efficacy in terms of survival for this cancer. Previous study focused on the development of a new therapy by non thermal plasma showed significant effects on tumor growth for colorectal carcinoma and glioblastoma. To allow targeted treatment, a fibered plasma (Plasma Gun) was developed and its evaluation was performed on an orthotopic mouse model of human pancreatic carcinoma using a MIA PaCa2-luc bioluminescent cell line. The aim of this study was to characterize this pancreatic carcinoma model and to determine the effects of Plasma Gun alone or in combination with gemcitabine. During a 36 days period, quantitative BLI could be used to follow the tumor progression and we demonstrated that plasma gun induced an inhibition of MIA PaCa2-luc cells proliferation in vitro and in vivo and that this effect could be improved by association with gemcitabine possibly thanks to its radiosensitizing properties.

Mucin-based targeted pancreatic cancer therapy

The prognosis of pancreatic cancer (PC) patients is very poor with a five-year survival of less than 5%. One of the major challenges in developing new therapies for PC is the lack of expression of specific markers by pancreatic tumor cells. Mucins are heavily Oglycosylated proteins characterized by the presence of short stretches of amino acid sequences repeated several times in tandem. The expression of several mucins including MUC1, MUC4, MUC5AC, and MUC16 is strongly upregulated in PC. Recent studies have also demonstrated a link between the aberrant expression and differential overexpression of mucin glycoproteins to the initiation, progression, and poor prognosis of the disease. These studies have led to increasing recognition of mucins as potential diagnostic markers and therapeutic targets in PC. In this focused review we present an overview of the therapies targeting mucins in PC, including immunotherapy (i.e. vaccines, antibodies, and radioimmunoconjugates), gene therapy, and other novel therapeutic strategies.

Fractionated radioimmunotherapy with (90) Y-clivatuzumab tetraxetan and low-dose gemcitabine is active in advanced pancreatic cancer: A phase 1 trial

BACKGROUND

It has been demonstrated that the humanized clivatuzumab tetraxetan (hPAM4) antibody targets pancreatic ductal carcinoma selectively. After a trial of radioimmunotherapy that determined the maximum tolerated dose of single-dose yttrium-90-labeled hPAM4 ((90) Y-hPAM4) and produced objective responses in patients with advanced pancreatic ductal carcinoma, the authors studied fractionated radioimmunotherapy combined with low-dose gemcitabine in this disease.

METHODS

Thirty-eight previously untreated patients (33 patients with stage IV disease and 5 patients with stage III disease) received gemcitabine 200 mg/m(2) weekly for 4 weeks with (90) Y-hPAM4 given weekly in Weeks 2, 3, and 4 (cycle 1), and the same cycle was repeated in 13 patients (cycles 2-4). In the first part of the study, 19 patients received escalating weekly (90) Y doses of 6.5 mCi/m(2) , 9.0 mCi/m(2) , 12.0 mCi/m(2) , and 15.0 mCi/m(2) . In the second portion, 19 additional patients received weekly doses of 9.0 mCi/m(2) or 12.0 mCi/m(2) .

RESULTS

Grade 3/4 thrombocytopenia or neutropenia (according to version 3.0 of the National Cancer Institute's Common Terminology Criteria for Adverse Events) developed in 28 of 38 patients after cycle 1 and in all retreated patients; no grade >3 nonhematologic toxicities occurred. Fractionated dosing of cycle 1 allowed almost twice the radiation dose compared with single-dose radioimmunotherapy. The maximum tolerated dose of (90) Y-hPAM4 was 12.0 mCi/m(2) weekly for 3 weeks for cycle 1, with ≤9.0 mCi/m(2) weekly for 3 weeks for subsequent cycles, and that dose will be used in future trials. Six patients (16%) had partial responses according to computed tomography-based Response Evaluation Criteria in Solid Tumors, and 16 patients (42%) had stabilization as their best response (58% disease control). The median overall survival was 7.7 months for all 38 patients, including 11.8 months for those who received repeated cycles (46% [6 of 13 patients] ≥1 year), with improved efficacy at the higher radioimmunotherapy doses.

CONCLUSIONS

Fractionated radioimmunotherapy with (90) Y-hPAM4 and low-dose gemcitabine demonstrated promising therapeutic activity and manageable myelosuppression in patients with advanced pancreatic ductal carcinoma.

Local control of experimental malignant pancreatic tumors by treatment with a combination of chemotherapy and intratumoral 224radium-loaded wires releasing alpha-emitting atoms

We developed (224)Ra-loaded wires that when inserted into solid tumors, release radioactive atoms that spread in the tumor and irradiate it effectively with alpha particles (diffusing alpha-emitters radiation therapy [DaRT]). In this study, we tested the ability of intratumoral (224)Ra-loaded wires to control the local growth of pancreatic tumors and the enhancement of this effect by chemotherapy. Pancreatic mouse tumors (Panc02) were treated with (224)Ra-loaded wire(s) with or without gemcitabine. The tumor size and survival were monitored, and autoradiography was performed to evaluate the spread of radioactive atoms inside the tumor. Mouse and human pancreatic cancer cells, irradiated in vitro by alpha particles with or without chemotherapy, were evaluated for cell growth inhibition. The insertion of (224)Ra-loaded wires into pancreatic tumors in combination with gemcitabine achieved significant local control and was superior to each treatment alone. A dosimetric analysis showed the spread of radioactive atoms in the tumor around the wires. Alpha particles combined with gemcitabine or 5-FU killed mouse and human cells in vitro better than each treatment alone. DaRT in combination with gemcitabine was proven effective against pancreatic tumors in vivo and in vitro, and the process may be applicable as a palliative treatment for patients with pancreatic cancer.

Treatment of advanced pancreatic carcinoma with 90Y-Clivatuzumab Tetraxetan: a phase I single-dose escalation trial

PURPOSE

Humanized antibody hPAM4 specifically binds a mucin glycoprotein expressed in pancreatic adenocarcinomas. This phase I study evaluated a single dose of (90)Y-clivatuzumab tetraxetan ((90)Y-labeled hPAM4) in patients with advanced pancreatic cancer.

EXPERIMENTAL DESIGN

Twenty-one patients (4 stage III; 17 stage IV) received (111)In-hPAM4 for imaging and serum sampling before (90)Y-hPAM4. Study procedures evaluated adverse events, safety laboratories, computed tomography (CT) scans, biomarkers, pharmacokinetics, radiation dosimetry, and immunogenicity (HAHA).

RESULTS

(111)In-hPAM4 showed normal biodistribution with radiation dose estimates to red marrow and solid organs acceptable for radioimmunotherapy and with tumor targeting in 12 patients. One patient withdrew before (90)Y-hPAM4; otherwise, 20 patients received (90)Y doses of 15 (n = 7), 20 (n = 9), and 25 mCi/m(2) (n = 4). Treatment was well tolerated; the only significant drug-related toxicities were (NCI CTC v.3) grade 3 to 4 neutropenia and thrombocytopenia increasing with (90)Y dose. There were no bleeding events or serious infections, and most cytopenias recovered to grade 1 within 12 weeks. Three patients at 25 mCi/m(2) encountered dose-limiting toxicity with grade 4 cytopenias more than 7 days, establishing 20 mCi/m(2) as the maximal tolerated (90)Y dose. Two patients developed HAHA of uncertain clinical significance. Most patients progressed rapidly and with CA19-9 levels increasing within 1 month of therapy, but 7 remained progression-free by CT for 1.5 to 5.6 months, including 3 achieving transient partial responses (32%-52% tumor diameter shrinkage).

CONCLUSION

(90)Y-Clivatuzumab tetraxetan was well tolerated with manageable hematologic toxicity at the maximal tolerated (90)Y dose, and is a potential new therapeutic for advanced pancreatic cancer.

MUC1 immunotherapy

The overexpression and aberrant glycosylation of MUC1 is associated with a wide variety of cancers, making it an ideal target for immunotherapeutic strategies. This review highlights the main avenues of research in this field, focusing on adenocarcinomas, from the preclinical to clinical; the problems and possible solutions associated with each approach; and speculates on the direction of MUC1 immunotherapeutic research over the next 5-10 years.

Imaging tumor variation in response to photodynamic therapy in pancreatic cancer xenograft models

PURPOSE

A treatment monitoring study investigated the differential effects of orthotopic pancreatic cancer models in response to interstitial photodynamic therapy (PDT), and the validity of using magnetic resonance imaging as a surrogate measure of response was assessed.

METHODS AND MATERIALS

Different orthotopic pancreatic cancer xenograft models (AsPC-1 and Panc-1) were used to represent the range of pathophysiology observed in human beings. Identical dose escalation studies (10, 20, and 40J/cm) using interstitial verteporfin PDT were performed, and magnetic resonance imaging with T2-weighted and T1-weighted contrast were used to monitor the total tumor volume and the vascular perfusion volume, respectively.

RESULTS

There was a significant amount of necrosis in the slower-growing Panc-1 tumor using high light dose, although complete necrosis was not observed. Lower doses were required for the same level of tumor kill in the faster-growing AsPC-1 cell line.

CONCLUSIONS

The tumor growth rate and vascular pattern of the tumor affect the optimal PDT treatment regimen, with faster-growing tumors being relatively easier to treat. This highlights the fact that therapy in human beings shows a heterogeneous range of outcomes, and suggests a need for careful individualized treatment outcomes assessment in clinical work.

Combination of conditionally replicative adenovirus and standard chemotherapies shows synergistic antitumor effect in pancreatic cancer

Due to devastating prognosis, novel therapies are needed for pancreatic cancer. We are in preparation for a human clinical trial of a conditionally replicative adenovirus (CRAd) we developed. While most patients in the target population are receiving either gemcitabine or 5-fluorouracil chemotherapy, the combination with CRAd has not yet been studied. This study was designed to evaluate combination therapies with CRAd and current standard chemotherapies in pancreatic cancer. When the combination therapy was tested in vitro, gemcitabine pretreatment showed a synergistic effect in two out of four cell lines whereas CRAd followed by gemcitabine exhibited a synergistic effect in one cell line. With 5-fluorouracil, pretreatment with 5-fluorouracil produced a synergistic effect in three cell lines whereas post-treatment was synergistic in only one cell line. These effects were not fully explained by either induction of cyclooxygenase (Cox) 2 activity or adenoviral receptors with chemotherapeutics. In in vivo analyses with Hs766T xenograft, 5-fluorouracil slightly improved the CRAd antitumor effect but it was not significant. Pretreatment with gemcitabine embodied a significant tumor reduction compared with single therapy with gemcitabine. The most significant antitumor effect occurred when tumors were treated with 5/3COX2CRAdF and subsequent gemcitabine (P = 0.001 vs gemcitabine alone, P = 0.012 vs 5/3COX2CRAdF alone) at day 12. In MIA Paca-2, pretreatments with either 5-fluorouracil or gemcitabine improved the CRAd therapeutic effect when administered before CRAd injection (P = 0.03 and P = 0.01, respectively). These experiments indicate the possible benefit of combination therapies, and thus it is not necessary to interrupt chemotherapeutics when receiving CRAd therapy.

Potentiation of high-LET radiation by gemcitabine: targeting HER2 with trastuzumab to treat disseminated peritoneal disease

PURPOSE

Recent studies from this laboratory with (212)Pb-trastuzumab have shown the feasibility of targeted therapy for the treatment of disseminated peritoneal disease using (212)Pb as an in vivo generator of (212)Bi. The objective of the studies presented here was improvement of the efficacy of alpha-particle radioimmunotherapy using a chemotherapeutic agent.

EXPERIMENTAL DESIGN

In a series of experiments, a treatment regimen was systematically developed in which athymic mice bearing i.p. LS-174T xenografts were injected i.p. with gemcitabine at 50 mg/kg followed by (212)Pb radioimmunotherapy.

RESULTS

In a pilot study, tumor-bearing mice were treated with gemcitabine and, 24 to 30 h later, with 5 or 10 muCi (212)Pb-trastuzumab. Improvement in median survival was observed at 5 microCi (212)Pb-trastuzumab in the absence (31 days) or presence (51 days) of gemcitabine: 45 and 70 days with 10 microCi versus 16 days for untreated mice (P < 0.001). Multiple doses of gemcitabine combined with a single (212)Pb radioimmunotherapy (10 microCi) administration was then evaluated. Mice received three doses of gemcitabine: one before (212)Pb-trastuzumab and two afterwards. Median survival of mice was 63 versus 54 days for those receiving a single gemcitabine dose before radioimmunotherapy (P < 0.001), specifically attributable to (212)Pb-trastuzumab (P = 0.01). Extending these findings, one versus two treatment cycles was compared. A cycle consisted of sequential treatment with gemcitabine, 10 microCi (212)Pb radioimmunotherapy, then one or two additional gemcitabine doses. In the first cycle, three doses of gemcitabine resulted in a median survival of 90 versus 21 days for the untreated mice. The greatest benefit was noted after cycle 2 in the mice receiving 10 microCi (212)Pb-trastuzumab and two doses of gemcitabine with a median survival of 196.5 days (P = 0.005). Pretreatment of tumor-bearing mice with two doses of gemcitabine before (212)Pb radioimmunotherapy was also assessed with gemcitabine injected 72 and 24 h before (212)Pb-trastuzumab. The median survival was 56 and 76 days with one and two doses of gemcitabine versus 49 days without gemcitabine. The effect may not be wholly specific to trastuzumab because (212)Pb-HuIgG with two doses of gemcitabine resulted in a median survival of 66 days (34 days without gemcitabine).

CONCLUSIONS

Treatment regimens combining chemotherapeutics with high-LET targeted therapy may have tremendous potential in the management and care of cancer patients.

Novel radiolabeled antibody conjugates

This article reviews the development of radioimmunoconjugates as a new class of cancer therapeutics. Numerous conjugates involving different antigen targets, antibody forms, radionuclides and methods of radiochemistry have been studied in the half-century since radioactive antibodies were first used in model systems to selectively target radiation to tumors. Whereas directly conjugated antibodies, fragments and subfragments have shown promise preclinically, the same approaches have not gained success in patients except in radiosensitive hematological neoplasms, or in settings involving minimal or locoregional disease. The separation of tumor targeting from the delivery of the therapeutic radionuclide in a multistep process called pretargeting has the potential to overcome many of the limitations of conventional, or one-step, radioimmunotherapy, with initial preclinical and clinical data showing increased sensitivity, specificity and higher radiation doses delivered. Our particular focus in pretargeting is the use of bispecific, trimeric (three Fab's) constructs made by a new antibody engineering method termed 'dock-and-lock.

Combination therapy using gemcitabine and radioimmunotherapy in nude mice with small peritoneal metastases of colonic origin

INTRODUCTION

Gemcitabine has been shown to exert a radiosensitizing effect in various epithelial cancers. The aim of the present studies was to investigate whether the efficacy of radioimmunotherapy (RIT) using the (131)I-labeled anti-CEA monoclonal antibody (MAb) MN-14 could be enhanced by coadministration of gemcitabine in nude mice with small (1-3 mm) peritoneal metastases of colonic origin.

MATERIALS AND METHODS

Firstly, the maximum tolerated dose (MTD) of gemcitabine was determined, when administered intraperitoneally at two different dosing schedules (0.11-3.0 mg/mouse/administration on days 0, 3, 6, and 9, or 0.022-0.60 mg/mouse/administration on days 0, 1, 2, 3, and 4). In two separate therapy studies in which these two administration regimens were applied, the efficacy of gemcitabine monotherapy was compared to that of RIT alone (125 muCi (131)I-MN-14/mouse) or RIT combined with gemcitabine.

RESULTS

When administered every 3rd day for a total of 4 administrations, or daily for 5 consecutive days, the gemcitabine was considered safe at 0.33 mg/mouse/administration and 0.066 mg/mouse/administration, respectively. In the first therapy study, median survival of the control mice was 39 days. Gemcitabine monotherapy at 0.11 mg or 0.33 mg/mouse/administration every 3rd day (total, 4 administrations) resulted in a median survival of 52 and 57 days, respectively (p = 0.0003, compared to controls). RIT alone resulted in a median survival of 66 days (p < 0.0001, compared to controls). The combination of RIT and gemcitabine coadministration resulted in a median survival of 73 and 94 days, respectively (p = 0.12, for trend). In the second therapy study, median survival of the control mice was 48 days, which was similar to the median survival of the mice treated with daily administrations of gemcitabine monotherapy at 0.022 mg/mouse/administration on 5 consecutive days (49 days; p = 0.17). RIT alone resulted in a significantly improved median survival of 66 days (p= = 0.0010, compared to controls). Combination therapy using RIT and gemcitabine resulted in a median survival of 64 days, which did not differ significantly from the survival of the mice treated with RIT alone (p = 0.43).

CONCLUSIONS

At the dose regimens employed, gemcitabine did not enhance the efficacy of RIT of experimental small-volume peritoneal carcinomatosis of colonic origin.

Combination therapy using the cyclooxygenase-2 inhibitor Parecoxib and radioimmunotherapy in nude mice with small peritoneal metastases of colonic origin

BACKGROUND

Inhibition of the COX-2 enzyme has been shown to have a radiosensitizing effect in epithelial cancers. The aim of this study was to investigate whether the efficacy of radioimmunotherapy (RIT) using 131I-labeled anti-CEA monoclonal antibody MN-14 could be enhanced by co-administration of the selective COX-2 inhibitor Parecoxib in mice with small volume (1-3 mm) peritoneal carcinomatosis of colonic origin.

METHODS

First, the efficacy of 14 daily injections of Parecoxib monotherapy (0-0.2-1.0-5.0-25.0 mg/kg) was determined in mice with intraperitoneal LS174T xenografts. Second, the influence of Parecoxib (1.0 or 5.0 mg/kg) on the biodistribution of 125I-MN-14 was assessed. Finally, the efficacy of RIT alone [125 microCi 131I-MN-14/mouse approximately 1/4 of the maximal tolerated dose (MTD)] was compared with that of Parecoxib monotherapy and RIT combined with daily injections of Parecoxib (1.0 or 5.0 mg/kg).

RESULTS

Parecoxib had no measurable antitumor effect up to the highest dose level (25 mg/kg). Parecoxib had no effect on the uptake of 125I-MN-14 in the intraperitoneal tumor xenografts or on normal tissue distribution. Median survival of the control mice and the mice treated with Parecoxib monotherapy (1.0 or 5.0 mg/kg) was 48.5 days, 52 days and 52 days (P=0.47). RIT alone significantly delayed the growth of the intraperitoneal xenografts resulting in a median survival of 87 days (P<0.0001). Mice treated with RIT + Parecoxib at 1.0 or 5.0 mg/kg had a median survival of 73.5 days and 76 days, respectively, which was not statistically different from survival after RIT alone (P=0.15).

CONCLUSION

The COX-2 inhibitor Parecoxib does not enhance the therapeutic efficacy of RIT of experimental small volume peritoneal carcinomatosis of colonic origin.

Does Paclitaxel (Taxol) Given after 111In-Labeled Monoclonal Antibodies Increase Tumor-Cumulated Activity in Epithelial Cancers?

PURPOSE

Paclitaxel synergized radiolabeled monoclonal antibodies, enhancing therapeutic effect in studies in mice with human xenografts. Paclitaxel was also observed to increase tumor uptake in imaging studies of (111)In-DOTA-Gly3Phe-m170 in patients with breast and prostate cancers. Further evaluations of tissue-cumulated activities, therapeutic indices, and pharmacokinetics were done using data for patients with breast and prostate cancer and for mice with human breast cancer xenografts.

EXPERIMENTAL DESIGN

In radioimmunotherapy trials, 12 patients with breast or prostate cancer were given two imaging doses (5 mCi each) of (111)In-DOTA-Gly3Phe-m170 1 week apart. Five of these patients were given a single dose of paclitaxel i.v. (75 mg/m2) 2 days after the second dose of (111)In. In a subsequent study, athymic mice with human breast cancer xenografts were given (111)In-DOTA-Gly3Phe-ChL6 alone, or in combination with daily paclitaxel i.p. (300 microg) one or more times. Pharmacokinetics were studied for at least 6 days in patients and 5 days in mice. Cumulated activities were determined for tumors and normal tissues.

RESULTS

Tumor-cumulated activity for every patient in the paclitaxel-treated group increased for the second dose of (111)In-DOTA-Gly3Phe-m170. The median ratio of cumulated activities in tumors for imaging dose 2 to those for dose 1 was 1.0 (0.8-1.3) in patients that were not given paclitaxel and 1.3 (1.2-1.4) in patients given paclitaxel. Normal tissue-cumulated activities were not different for the two doses. Mice given paclitaxel 1 day after (111)In-DOTA-Gly3Phe-ChL6 also showed an increase in tumor-cumulated activity, 22.9 (+/- 1.3) versus 19.4 (+/- 3.3) microCi h/g/microCi (P = 0.05). Cumulated activities of normal tissues were similar for all groups of mice.

CONCLUSIONS

Paclitaxel given 1 to 2 days after (111)In-DOTA-Gly3Phe-monoclonal antibody increased the tumor-cumulated activity in patients and in mice with epithelial cancers and did not alter cumulated activities in normal tissues.

Overexpression of MUC13 is associated with intestinal-type gastric cancer

Mucins are secreted or transmembrane glycoproteins that are expressed mainly in the digestive tract. This family of proteins has been the focus of much gastric cancer research as some transmembrane mucins are implicated in tumorigenesis and make attractive targets for cancer diagnosis and therapeutics. Mucins have also been utilized to classify gastric cancer by differentiating between gastric and intestinal phenotypes. Here we show that transmembrane mucin MUC13 is upregulated in gastric cancer. By quantitative real-time reverse transcription-polymerase chain reaction and immunoblot analysis, overexpression of MUC13 was verified in more than half of the samples examined. In immunohistochemical analysis, MUC13 staining was observed in 74 of 114 cases of gastric cancer (64.9%), predominantly in intestinal type (P < 0.001), and in 9 of 10 cases of intestinal metaplasia, precancerous lesions of intestinal-type gastric cancer, but not observed in normal gastric mucosa. Moreover, MUC13 staining patterns characteristic of histological type were identified: staining was on the apical side of tubular glands in intestinal type and on the cytoplasm in diffuse type. These results suggest that MUC13 is a good differentiation marker for gastrointestinal mucosa and that it may have a causal role that correlates with two distinct gastric tumorigenesis pathways.

T cells recognize PD(N/T)R motif common in a variable number of tandem repeat and degenerate repeat sequences of MUC1

The tumor-associated antigen MUC1 is a transmembrane glycoprotein, which is overexpressed in human carcinomas. Peptide epitopes, containing the PDTR fragment from the variable number of tandem repeat (VNTR) domains of MUC1 have been found to be immunodominant in T-cell and B-cell responses. However, little is known about the immunogenicity and specificity of T-cell epitopes from other regions of MUC1 that may also participate in immune responses against tumors. In this study, the combination of immunoinformatics, molecular modeling and a vaccine adjuvant strategy were used to predict and describe a novel T-cell epitope, SAPDNRPAL, located within the degenerate tandem repeat of MUC1. This peptide possesses structural similarity to both VNTR-derived SAPDTRPAP and Sendai virus peptide FAPGNYPAL, which are known to induce cytotoxic T lymphocytes (CTL). We found that SAPDNRPAL had a higher affinity for mouse H-D(b), H-2K(b) and human HLA-A2 molecules than SAPDTRPAP. A chimeric peptide (CP) containing SAPDNRPAL and an adjuvant C5a-derived decapeptide induced epitope-specific type 1 T cells in human MUC1 transgenic mice (ELISPOT). Mice that received dendritic cells (DC) pulsed with the CP or a 25-mer peptide containing the SAPDNRPAL sequence showed increased frequencies of SAPDNRPAL- and SAPDTRPAP-specific interferon-gamma producing T cells. PDTR-specific antibody 214D4 reacted with both SAPDNRPAL and SAPDTRPAP (ELISA). Altogether, our data suggest that the degenerate MUC1 repeat sequence contains the immunogenic T-cell epitope SAPDNRPAL, which is cross-reactive with the VNTR-derived peptide SAPDTRPAP. We suggest that the use of immunogenic PDNR-containing epitope(s) in vaccine strategies could be beneficial for developing increased, PD(N/T)R motif-specific T-cell responses against tumors expressing MUC1.

Pancreatic enzyme extract improves survival in murine pancreatic cancer

OBJECTIVES

The disappointing current therapeutic approaches for pancreatic cancer (PC) represent an urgent need for the development of novel methods to control the disease. Based on a recent report on the effectiveness of pancreatic enzyme therapy, we examined the effect of porcine pancreatic enzyme extracts (PPE) on human PC xenografts in nude mice.

METHODS

The malignant human PC cell line AsPC1 was transplanted into the pancreas of male beige XID nude mice that were treated or not with PPE in drinking water. The survival, size, and volume of tumors, plasma pancreatic enzyme levels, fecal fat, and urine were examined as were the expression of transforming growth factor alpha, insulinlike growth factor-I, epidermal growth factor, epidermal growth factor receptor, apoptosis, and proliferation rate of tumor cells.

RESULTS

PPE-treated mice survived significantly longer than the control group (P < 0.002). Tumors in the PPE-treated group were significantly smaller than in the control group. All mice in the control group showed steatorrhea, hyperglucosuria, hyperbilirubinuria, and ketonuria at early stages of tumor growth, whereas only a few in the treated group showed some of these abnormalities at the final stage. There were no differences in the expression of growth factors, epidermal growth factor receptor, or the apoptotic rate between the tumors of treated and control mice.

CONCLUSIONS

The treatment with PPE significantly prolongs the survival of mice with human PC xenografts and slows the tumor growth. The data indicate that the beneficial effect of PPE on survival is primarily related to the nutritional advantage of the treated mice.

Combined 90Yttrium-DOTA-labeled PAM4 antibody radioimmunotherapy and gemcitabine radiosensitization for the treatment of a human pancreatic cancer xenograft

We have examined the application of (90)Y-DOTA-cPAM4, anti-MUC1 IgG, in combination with the front-line drug gemcitabine as a potential therapeutic for pancreatic cancer. Athymic nude mice bearing CaPan1 human pancreatic cancer xenografts were administered 2 mg of gemcitabine on days 0, 3, 6, 9 and 12 with concurrent (90)Y-DOTA-cPAM4 (100 microCi) provided on day 0. A second group of mice received a second cycle of treatment 5 weeks after the start of the first cycle. Control groups of mice included those that received either treatment arm alone, the combined modality treatment employing a nontargeting control antibody (hLL2, anti-B-cell lymphoma) and a final group that was left untreated. Gemcitabine administered as a single agent provided no antitumor effect. A single cycle of the combined (90)Y-DOTA-cPAM4 and gemcitabine treatment provided greater inhibition of tumor growth than was observed for any of the other treatment procedures. Tumor growth was delayed for a period of 7 weeks. Two cycles of gemcitabine with concomitant (90)Y-DOTA-cPAM4 yielded significant tumor regression and increased median survival to 21 weeks vs. 12 weeks for mice receiving a single cycle of therapy (p<0.024). Median tumor volume doubling-times were 18 weeks in mice treated with 2-cycles of therapy vs. 7 weeks in mice given only 1-cycle (p<0.001), and 3.5 weeks for the group that received 2-cycles of gemcitabine concomitant with equitoxic nontargeting (90)Y-DOTA-hLL2 (p<0.001). These data suggest that addition of (90)Y-DOTA-cPAM4 RAIT to a gemcitabine treatment regimen may provide enhanced antitumor efficacy for the treatment of pancreatic cancer.

MUC1 and MUC2 expression in salivary gland tumors and in non-neoplastic salivary gland tissue

The expression of MUC1 and MUC2 was studied in salivary gland tumors and non-neoplastic salivary gland tissue. Formalin-fixed paraffin-embedded specimens from 101 patients (21 pleomorphic adenomas (PA), 22 Warthin's tumors (WT), 26 adenoid cystic carcinomas (ACC), 13 acinic cell adenocarcinomas (ACA), 9 mucoepidermoid carcinomas (MC), and 10 specimens of non-neoplastic parotid and submandibular gland tissue) were immunostained. All salivary gland tumors expressed MUC1. A strong immunoreactivity was noted in WT and MC, a moderate in ACC and ACA, and a weak in PA. Strong expression of MUC2 was noted in all WT, moderate expression in MC, and weak expression in PA and ACA. All cases of ACC except for two were negative for MUC2. In general, MUC1 expression was stronger than that of MUC2. Non-neoplastic salivary gland tissue revealed a moderate MUC1 and MUC2 expression in excretory ducts and a strong expression in striated ducts. The apical plasma membrane of some serous acini expressed MUC1. Mucous acini were negative for both antigens. No change in immunoreactivity was noted in cases of chronic sclerosing sialadenitis. In conclusion, the different expression pattern of MUC1 and MUC2 in salivary gland neoplasia may be of additional value for the classification of salivary gland tumors.

Application of 99mTc labeled chimeric Fab fragments of monoclonal antibody A7 for immunoscintigraphy of pancreatic carcinoma

BACKGROUND

One of the reasons for the poor prognosis of pancreatic carcinoma is the difficulty of obtaining an early diagnosis of pancreatic carcinoma. One possibility is the application of radioimmunoscintigraphy using radiolabeled monoclonal antibodies (Mabs).

METHODS

We labeled chimeric (human/mouse) Fab fragments of Mab A7 (chA7Fab) with (99m)Tc and examined the distribution of (99m)Tc-labeled chA7Fab in nude mice bearing human pancreatic carcinoma.

RESULTS

The tumor accumulation of (99m)Tc-labeled chA7Fab was larger than that of (99m)Tc-labeled A7 from 2 to 6 hr after injection. (99m)Tc-labeled chA7Fab disappeared from blood more rapidly than (99m)Tc-labeled A7. For all resected normal tissues except kidney, the accumulation of (99m)Tc-labeled chA7Fab was low and similar to that of (99m)Tc-labeled A7.

CONCLUSIONS

Because the half-life of (99m)Tc is short (6 hr), chA7Fab, which accumulates rapidly in tumors, may be a better carrier of (99m)Tc than intact Mab A7.

Magnetic resonance imaging of the pancreas and pancreatic tumors in a mouse orthotopic model of human cancer

Pancreatic adenocarcinoma has a rising incidence and a very poor survival rate. To develop new treatment strategies, extensive research is performed on animal models of pancreatic cancer. Orthotopic pancreatic tumors models, where the tumor is implanted into the pancreas, resemble the human disease more closely than subcutaneous tumor models, yet are difficult to monitor. In our study we report a magnetic resonance imaging (MRI) approach to visualize the pancreas in mice and to monitor orthotopically implanted pancreatic tumors. An MRI scanner was used to image normal murine pancreas and the pancreas of mice implanted with a human pancreatic adenocarcinoma cell line. Gadolinium (Gd)-DTPA-enhanced T1- and T2-weighted standard sequences were used with the objective to identify the pancreas and to monitor the growth of orthotopic tumors during 30 days. The pancreas as well as the implanted tumors could be easily identified using MRI. On T2-weighted images, the implanted tumors were easily visualized at the implantation side with high signal intensity. After application of a contrast agent, the tumors showed an enhancement. Heterogeneities within the tumor could be delineated, corresponding to histology, and the size of the tumor could be measured precisely. MR serves as a noninvasive high-resolution image modality to monitor murine pancreas as well as size, growth and even areas of heterogeneity in orthotopic pancreatic tumors.

Antibody therapy of non-Hodgkin's B-cell lymphoma

Engineering antibodies with reduced immunogenicity and enhanced effector functions, and selecting antigen targets with the appropriate specificity, density, and/or functionality, have contributed to the recent clinical successes in using unconjugated "naked" antibody therapies of B-cell lymphoma (rituximab) and breast carcinoma (Herceptin). The non-overlapping toxicities of naked antibodies and chemotherapy, together with their potential synergy, which is based on unique and complementary mechanisms of action, have contributed to the creation of new standards of care in cancer therapy and management. Clinical trial results supporting these concepts are presented. Furthermore, the exquisite specificity of antibodies renders them ideal vehicles for selective delivery of toxic payloads such as drugs or radionuclides. Although successful in therapy of hematological cancers (Zevalin, Mylotarg), the broader application of these technologies to carcinomas still remains to be proven in clinical testing. Engineering of antibody constructs with optimal blood clearance and tumor-targeting kinetics, and selecting the radionuclide that may deliver sufficient radiation energy to kill the more radio-resistant carcinomas, are discussed. With the advent of genomics and proteomics, new membrane-associated tumor antigens are being discovered and will provide novel targets for future antibody therapy of cancer.