The radiation biology of radioimmunotherapy

The Use of Nanorobotics in the Treatment Therapy of Cancer and Its Future Aspects: A Review

The late Nobel Physicist Richard P. Feynman, in a dinner talk in 1959, very rightly said that there is enough room for the betterment of technology beyond our scope of imagination, proposing utilizing mechanical tools to make those that are relatively smaller than the others, which further can be rendered fruitful in making even more compact mechanical devices, all the way down to the level of the smallest known atom, emphasizing that this is "a progress which I believe cannot be avoided". Feynman proposed that nanomachines, nanorobots, and nanodevices may eventually be utilized to construct a huge range of atomically accurate microscopic instruments and manufacturing equipment, as well as a large number of ultra-small devices and other nanoscale and microscale robotic structures. Biotechnology, molecular biology, and molecular medicine could be used to create totally self-sufficient nanorobots/nanobots. Nanorobotics includes sophisticated submicron devices constructed of nanocomponents that are viewed as a magnificent desired future of health care. It has a promising potential in medication delivery technology for cancer, the top cause of mortality among those under the age of 85 years. Nanorobots might transport and distribute vast volumes of anticancer medications into diseased cells without hurting normal cells, decreasing the adverse effects of existing therapies such as chemotherapy damage. The ultimate development of this innovation, which will be accomplished via a close partnership among specialists in robotics, medicine, and nanotechnology, will have a significant influence on illness detection, therapy, and prophylaxis. This report includes a study on several ways to cancer therapy utilizing nanorobots. Furthermore, it offers insight into the future breadth of this area of research.

Preparation of 177Lu-Trastuzumab injection for treatment of breast cancer

The objective of this study was the facile preparation of ¹⁷⁷Lu-CHX-A''-DTPA-Trastuzumab injection for breast cancer therapy. Trastuzumab conjugated with CHX-A''-DTPA-NCS was radiolabeled with ¹⁷⁷Lu in >95% radiochemical purity. In vitro studies in SKBR3 and MDA-MB-453 cells confirmed specificity of ¹⁷⁷Lu-CHX-A''-DTPA-Trastuzumab to HER2 positive cells. The radioimmunoconjugate showed good immunoreactivity, in vitro stability in saline and K_d of 1.01 ± 0.13 nM in SKBR3 cells. Clearance of ¹⁷⁷Lu-CHX-A''-DTPA-Trastuzumab in Swiss mice was predominantly through the hepatobiliary route with minimal bone uptake.

90 Y-ibritumomab-tiuxetan as a therapeutic alternative for follicular lymphoma (FL): A single-center experience

BACKGROUND

Follicular lymphoma (FL) is the most frequent indolent lymphoma subtype in adults. Maintenance therapy with rituximab is frequently applied to FL patients with complete or partial response following initial chemoimmunotherapy. However, radioimmunotherapy with ⁹⁰ Y-ibritumomab-tiuxetan represents a therapeutic alternative.

METHODS

To compare the clinical and the prognostic impact of both therapies, a study collective of n = 56 patients diagnosed with indolent B-cell lymphoma was retrospectively investigated. The study collective was subdivided into two groups: n = 36 patients treated with rituximab maintenance therapy vs n = 20 patients treated with ⁹⁰ Y-ibritumomab-tiuxetan.

RESULTS

No prognostic differences for performance status, FLIPI score, gender, or B-symptoms were found for ⁹⁰ Y-ibritumomab-tiuxetan or rituximab maintenance therapy. Overall survival rates and progression-free survival did not differ between both maintenance therapies.

CONCLUSION

Our retrospective single-center analysis of two patient groups without major differences in prognostic parameters revealed similar outcome with two different maintenance therapies. Hence, ⁹⁰ Y-ibritumomab-tiuxetan therapy might offer a valuable alternative treatment option for FL patients with partial response. However, large prospective trials are needed to confirm the reported findings.

Safety and efficacy of radioimmunotherapy (RIT) in treatment of non-Hodgkin's lymphoma in the community setting

INTRODUCTION

Radioimmunotherapy (RIT) is a unique therapeutic modality that combines biologic and radiolytic mechanisms to induce tumor kill. RIT is underutilized in the community outpatient setting.

METHODS

This is an institutional review of patients treated with RIT at St. John Hospital and Medical Center (SJH&MC) 2003-2011. RIT agents were dosed according to recommended guidelines. Response was assessed using the Revised Response Criteria for Malignant Lymphoma and toxicity was assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events. The primary aim was to assess overall response rate (ORR) and overall survival (OS). The secondary aim was to assess the impact of variable host and disease factors on the ORR to RIT and OS.

RESULTS

Forty-eight patients were treated with RIT within the specified period at SJH&MC; of which 52% with follicular lymphoma (FL) and 46% with diffuse large B cell lymphoma (DLBCL). The majority of patients had relapsed or refractory disease (98%). Median duration of follow-up was 17 months. The ORR was 73% with 44% complete remission (CR) rate and OS of 48 months. The ORR was 79% with 58% CR rate and OS of 82 months among FL patients. Among DLBCL patients, the ORR was 65% with 30% CR rate and OS of 39 months. Response to last therapy before RIT was the only significant predictor of response to RIT and a significant predictor of OS in multivariate analyses. Prior exposure to EBRT did not predict response or survival in multivariate analyses. Toxicity was manageable and predominantly hematologic.

CONCLUSIONS

RIT is effective and feasible for use in the community outpatient setting.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Patients with B-cell NHL can safely receive RIT close to home. With some coordination of effort, it is not difficult for community-based cancer centers to implement this treatment modality.

Radioimmunotherapy for B-cell non-hodgkin lymphomas

BACKGROUND

Radioimmunotherapy (RIT) is a safe and effective therapeutic option for patients with indolent B-cell non-Hodgkin lymphomas (NHL), in both up-front and relapsed/refractory settings. Two approved agents (90Y-ibritumomab tiuxetan and 131I-tositumomab) are available in the United States. Both target CD20 with similar clinical outcomes but with unique clinical considerations and radiation precautions due to the use of varying radioisotopes.

METHODS

This paper reviews the available evidence for these approved RIT agents and examines the recently published and ongoing clinical trials of potential novel indications for aggressive B-cell NHL.

RESULTS

A pretreatment biodistribution evaluation required before administering the 90Y-ibritumomab tiuxetan therapeutic dose has been removed, which once limited its usage. The potential clinical applications of RIT include relapsed/refractory indolent B-cell NHL, diffuse large B-cell lymphoma, indolent lymphoma in the front-line setting, and mantle cell lymphoma. Multiple novel RIT agents are in preclinical and clinical development, and the addition of radiosensitizers or external-beam radiotherapy may act in synergy with RIT for both indolent and aggressive lymphomas. The risk of treatment-related myelodysplastic syndrome does not appear to be higher in patients treated with RIT over those receiving chemotherapy alone.

CONCLUSIONS

RIT is a safe, effective, and significantly underutilized therapy for patients with B-cell NHL, and many studies have demonstrated the efficacy of 90Y-ibritumomab tiuxetan and 131I-tositumomab for relapsed/refractory indolent B-cell lymphomas. Continued research to establish its efficacy for other lymphoma subtypes is warranted.

Radioimmunotherapy with ¹³¹I-bevacizumab as a specific molecule for cells with overexpression of the vascular endothelial growth factor

Bevacizumab is a humanized monoclonal antibody that inhibits vascular endothelial growth factor A and is used for the treatment of several cancers. We labeled this monoclonal antibody with Iodine-131 (¹³¹I) and performed in vitro quality control and tumor cell growth inhibition tests. Bevacizumab was labeled with ¹³¹I using chloramine T. Radiochemical purity and stability in phosphate-buffered saline and human blood serum were determined using thin-layer chromatography and radio-sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively, performed at different times. Cell-specific binding, internalization, and toxicity of the radiolabeled antibody were tested using the SKOV-3 ovarian cancer cell line. The biodistribution of ¹³¹I-bevacizumab was investigated using male mice. The radiochemical purity of the complex was 99% ± 0.7%. Its stability in phosphate-buffered saline and human blood serum at 48 hours postpreparation was 78% ± 1.2% and 93% ± 0.6%, respectively. (131)I-bevacizumab was significantly bound to SKOV-3. The internalization of ¹³¹I-bevacizumab was time dependent, and it was cleared from the blood after 24 hours. Significant reductions in SKOV-3 cell viability were achieved with (131)I-bevacizumab at a concentration of 500 nM. A low accumulation of ¹³¹I-bevacizumab was observed in the stomach and salivary glands after 24 hours and 48 hours. These findings indicate that the new radiolabeled antibody should be further evaluated in animals and, possibly, in humans as a new radiopharmaceutical agent for use in radioimmunotherapy for ovarian cancer.

Integrin targeted delivery of radiotherapeutics

Targeted radionuclide therapy, which is based on the selective delivery of a sufficient radiation dose to tumors without significantly affecting normal tissues, is a promising therapeutic approach for the treatment of a wide variety of malignancies. Integrins, a family of cell adhesion molecules, play key roles during tumor angiogenesis and metastasis. Among all the integrins, αvβ3 seems to be the most important in the process of tumor angiogenesis. Integrin αvβ3 is highly expressed on activated endothelial cells, new-born vessels as well as some tumor cells, but is not present in resting endothelial cells and most normal organ systems, making it a suitable target for anti-tumor therapy. In this review, we summarize the current development and applications of antibody-, peptide-, and other ligand-based integrin targeted radiotherapeutics for tumor radiation therapy.

Bortezomib-induced enzyme-targeted radiation therapy in herpesvirus-associated tumors

We investigated the possibility of using a pharmacologic agent to modulate viral gene expression to target radiotherapy to tumor tissue. In a mouse xenograft model, we had previously shown targeting of [(125)I]2'-fluoro-2'-deoxy-beta-D-5-iodouracil-arabinofuranoside ([(125)I]FIAU) to tumors engineered to express the Epstein-Barr virus thymidine kinase (EBV-TK). Here we extend those results to targeting of a therapeutic radiopharmaceutical [(131)I]FIAU to slow or stop tumor growth or to achieve tumor regression. These outcomes were achieved in xenografts with tumors that constitutively expressed the EBV-TK. With naturally infected EBV tumor cell lines (Burkitt's lymphoma and gastric carcinoma), activation of viral gene expression by pretreatment with bortezomib was required. Marked changes in tumor growth could also be achieved in naturally infected Kaposi's sarcoma herpesvirus tumors after pretreatment with bortezomib. Bortezomib-induced enzyme-targeted radiation therapy illustrates the possibility of pharmacologically modulating tumor gene expression to result in targeted radiotherapy.

Radiobiology of systemic radiation therapy

Although systemic radionuclide therapy (SRT) is effective as a palliative therapy in patients with metastatic cancer, there has been limited success in expanding patterns of utilization and in bringing novel systemic radiotherapeutic agents to routine clinical use. Although there are many factors that contribute to this situation, we hypothesize that a better understanding of the radiobiology and mechanism of action of SRT will facilitate the development of future compounds and the future designs of prospective clinical trials. If these trials can be rationalized to the biological basis of the therapy, it is likely that the long-term outcome would be enhanced therapeutic efficacy. In this review, we provide perspectives of the current state of low-dose-rate (LDR) radiation research and offer linkages where appropriate with current clinical knowledge. These include the recently described phenomena of low-dose hyper-radiosensitivity-increased radioresistance (LDH-IRR), adaptive responses, and biological bystander effects. Each of these areas require a major reconsideration of existing models for radiation action and an understanding of how this knowledge will integrate into the evolution of clinical SRT practice. Validation of a role in vivo for both LDH-IRR and biological bystander effects in SRT would greatly impact the way we would assess therapeutic response to SRT, the design of clinical trials of novel SRT radiopharmaceuticals, and risk estimates for both therapeutic and diagnostic radiopharmaceuticals. We believe that the current state of research in LDR effects offers a major opportunity to the nuclear medicine community to address the basic science of clinical SRT practice, to use this new knowledge to expand the use and roles of SRT, and to facilitate the introduction of new therapeutic radiopharmaceuticals.

Antibody-guided radiation therapy of cancer

Radioimmunotherapy (RIT) using radiolabeled monoclonal antibodies (MAbs) directed against tumor-associated antigens has evolved from an appealing concept to one of the standard treatment options for patients with non-Hodgkin's lymphoma (NHL). Inefficient localization of radiolabeled MAbs to nonhematological cancers due to various tumor-related factors, however, has refrained RIT from outgrowing the experimental stage in solid tumors. Still, small volume or minimal residual disease has been recognized as a potentially suitable target for radiolabeled antibodies. Several strategies are being explored aimed at improving the targeting of radiolabeled MAbs to solid tumors thus improving their therapeutic efficacy. In this review, a historical overview of the application of RIT is given and various aspects of the application of radiolabeled MAbs as anti-cancer agents are discussed. Finally, the clinical results of RIT of NHL, colorectal cancer, ovarian cancer, breast cancer, and renal cell cancer are reviewed.

The design and evaluation of a novel targeted drug delivery system using cationic emulsion-antibody conjugates

In an attempt to design a targeted drug delivery system to tumors' over-expressing H-ferritin specifically recognized by a monoclonal antibody, AMB8LK, a cationic emulsion - AMB8LK conjugate was prepared. A novel cross-linker molecule bearing maleimide group was synthesized and added to cationic emulsion formulation for AMB8LK Fab' fragment covalent coupling. NMR spectroscopy confirmed the cross-linker synthesis and the preservation of the active maleimide function. SDS gel-electrophoresis results corroborated the formation of the Fab' fragment. Different densities of Fab' fragments (10-200 Fab'/oil droplet) were conjugated to emulsion droplet interface and no changes in the physico-chemical properties were observed ( approximately 120 nm size and zeta potential of approximately +30 mV). The coupling efficiency ranged from 55% to 70% and was visualized by TEM showing gold particles attached to the droplet interface. Cell culture studies demonstrated specific binding to cells as confirmed by the occurrence of the marked reduction in binding when free AMB8LK Mab was incubated before adding the AMB8LK-emulsion conjugate to the cells. The coupling of AMB8LK Fab' fragment to the cationic emulsion increased the cells uptake by 50% as compared to non-conjugated respective cationic emulsion. Appropriate conditions were, thus, identified for coupling AMB8LK Fab' fragment to cationic emulsion without altering the specificity and affinity of the Mab fragment to the tumor antigen.

Radioimmunotherapy and colorectal cancer

BACKGROUND

Despite the success of radioimmunotherapy (RIT) using radiolabelled monoclonal antibodies (Mabs) directed against tumour-associated antigens in the treatment of non-Hodgkin's lymphoma, therapeutic success in solid tumours has been modest. In the past decade, a dozen Mabs have been investigated clinically for their potential usefulness in RIT of colorectal cancer.

METHODS

The application of radiolabelled Mabs for the treatment of solid cancers is discussed, and clinical trials investigating RIT for colorectal cancer listed in the Medline and Embase databases are reviewed.

RESULTS

Uptake of radiolabelled Mabs in tumour and, consequently, the therapeutic efficacy of RIT is inversely correlated with tumour size. The bone marrow is the most important dose-limiting organ. Twenty-three phase I/II studies were found that investigated the feasibility and efficacy of RIT using five radionuclides and 15 Mabs against carcinoembryonic antigen, tumour-associated glycoprotein 72, epithelial cellular adhesion molecule, A33 or colon-specific antigen p, mainly in patients with advanced colorectal cancer. A few responses were recorded but no particular antibody construct seemed superior.

CONCLUSION

RIT might be an effective adjuvant treatment modality in colorectal cancer. Future studies should focus on its application in patients with small-volume or minimal residual disease.