Radiolabeled antibodies in renal cell carcinoma

Clinical practice guidelines for molecular tumor marker, 2nd edition review part 2

In recent years, rapid advancement in gene/protein analysis technology has resulted in target molecule identification that may be useful in cancer treatment. Therefore, "Clinical Practice Guidelines for Molecular Tumor Marker, Second Edition" was published in Japan in September 2021. These guidelines were established to align the clinical usefulness of external diagnostic products with the evaluation criteria of the Pharmaceuticals and Medical Devices Agency. The guidelines were scoped for each tumor, and a clinical questionnaire was developed based on a serious clinical problem. This guideline was based on a careful review of the evidence obtained through a literature search, and recommendations were identified following the recommended grades of the Medical Information Network Distribution Services (Minds). Therefore, this guideline can be a tool for cancer treatment in clinical practice. We have already reported the review portion of "Clinical Practice Guidelines for Molecular Tumor Marker, Second Edition" as Part 1. Here, we present the English version of each part of the Clinical Practice Guidelines for Molecular Tumor Marker, Second Edition.

Imaging using radiolabelled targeted proteins: radioimmunodetection and beyond

The use of radiolabelled antibodies was proposed in 1970s for staging of malignant tumours. Intensive research established chemistry for radiolabelling of proteins and understanding of factors determining biodistribution and targeting properties. The use of radioimmunodetection for staging of cancer was not established as common practice due to approval and widespread use of [¹⁸F]-FDG, which provided a more general diagnostic use than antibodies or their fragments. Expanded application of antibody-based therapeutics renewed the interest in radiolabelled antibodies. RadioimmunoPET emerged as a powerful tool for evaluation of pharmacokinetics of and target engagement by biotherapeutics. In addition to monoclonal antibodies, new radiolabelled engineered proteins have recently appeared, offering high-contrast imaging of expression of therapeutic molecular targets in tumours shortly after injection. This creates preconditions for noninvasive determination of a target expression level and stratification of patients for targeted therapies. Radiolabelled proteins hold great promise to play an important role in development and implementation of personalised targeted treatment of malignant tumours. This article provides an overview of biodistribution and tumour-seeking features of major classes of targeting proteins currently utilized for molecular imaging. Such information might be useful for researchers entering the field of the protein-based radionuclide molecular imaging.

Evaluation of Radiolabeled Girentuximab In Vitro and In Vivo

Girentuximab (cG250) targets carbonic anhydrase IX (CAIX), a protein which is expressed on the surface of most renal cancer cells (RCCs). cG250 labeled with 177Lu has been used in clinical trials for radioimmunotherapy (RIT) of RCCs. In this work, an extensive characterization of the immunoconjugates allowed optimization of the labeling conditions with 177Lu while maintaining immunoreactivity of cG250, which was then investigated in in vitro and in vivo experiments. cG250 was conjugated with S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (DOTA(SCN)) by using incubation times between 30 and 90 min and characterized by mass spectrometry. Immunoconjugates with five to ten DOTA(SCN) molecules per cG250 molecule were obtained. Conjugates with ratios less than six DOTA(SCN)/cG250 had higher in vitro antigen affinity, both pre- and postlabeling with 177Lu. Radiochemical stability increased, in the presence of sodium ascorbate, which prevents radiolysis. The immunoreactivity of the radiolabeled cG250 tested by specific binding to SK-RC-52 cells decreased when the DOTA content per conjugate increased. The in vivo tumor uptake was < 10% ID/g and independent of the total amount of protein in the range between 5 and 100 µg cG250 per animal. Low tumor uptake was found to be due to significant necrotic areas and heterogeneous CAIX expression. In addition, low vascularity indicated relatively poor accessibility of the CAIX target.

An update on anticancer drug development and delivery targeting carbonic anhydrase IX

The expression of carbonic anhydrase (CA) IX is up-regulated in many types of solid tumors in humans under hypoxic and acidic microenvironment. Inhibition of CA IX enzymatic activity with selective inhibitors, antibodies or labeled probes has been shown to reverse the acidic environment of solid tumors and reduce the tumor growth establishing the significant role of CA IX in tumorigenesis. Thus, the development of potent antitumor drugs targeting CA IX with minimal toxic effects is important for the target-specific tumor therapy. Recently, several promising antitumor agents against CA IX have been developed to treat certain types of cancers in combination with radiation and chemotherapy. Here we review the inhibition of CA IX by small molecule compounds and monoclonal antibodies. The methods of enzymatic assays, biophysical methods, animal models including zebrafish and Xenopus oocytes, and techniques of diagnostic imaging to detect hypoxic tumors using CA IX-targeted conjugates are discussed with the aim to overview the recent progress related to novel therapeutic agents that target CA IX in hypoxic tumors.

Next revolution in molecular theranostics: personalized medicine for urologic cancers

Extensive lists of molecular biomarkers are currently evaluated as potential targets for directed cancer therapies. We reviewed three potential candidate biomarkers to play a role in the near future as molecular theranostics for urologic malignancies. Carbonic anhydrase type IX is a surrogate marker of hypoxia highly expressed in cancer cells. Their expression and clinical significance in kidney and urothelial bladder cancer are discussed as well as the main therapeutic approaches that are currently under evaluation. For prostate cancer, available evidence on the use of prostate-specific membrane antigen and neuropeptide receptors radiolabeled analog and the undergoing clinical studies are also analyzed and discussed at different stages of prostate cancer.

Analysis of TMEM174 gene expression in various renal cancer types by RNA in situ hybridization

Transmembrane protein 174 (TMEM174) mRNA is easily detectable in human kidney tissues and activates AP-1 and promotes 293T cell proliferation. In the present study, RNA in situ hybridization was used to detect TMEM174 gene expression in various malignant renal cancer and normal renal tissues. The results showed that TMEM174 exhibits differential expression in renal tissues, with a high positive rate of expression in squamous cell carcinoma with necrosis, papillary renal cell carcinoma and transitional cell carcinoma, and a low positive rate of expression in clear cell carcinoma, interstitial nephritis, undifferentiated carcinoma, retroperitoneal metastatic clear cell carcinoma, adrenal gland metastatic clear cell carcinoma, pelvic cavity metastatic chromophobe carcinoma, severe atypical hyperplasia of transitional epithelium and hyperplasia. Extremely weak expression was exhibited in collecting duct carcinoma, Wilms’ tumor, chronic pyelonephritis, acute pyelonephritis, cancer adjacent normal renal tissue and normal renal tissue. In conclusion, the TMEM174 gene exhibited high expression levels in certain renal carcinomas, which may indicate that TMEM174 may have a significant role in the development and progression of these renal carcinomas.

Agents described in the Molecular Imaging and Contrast Agent Database for imaging carbonic anhydrase IX expression

Carbonic anhydrase IX (CA IX) is selectively expressed in a range of hypoxic tumours and is a validated endogenous hypoxia marker with prognostic significance; hence, CA IX is of great interest as a molecular imaging target in oncology. In this review, we present an overview of the different imaging agents and imaging modalities that have been applied for the in vivo detection of CA IX. The imaging agents reviewed are all entries in the Molecular Imaging and Contrast Agent Database (MICAD) and comprise antibody, antibody fragments and small molecule imaging agents. The effectiveness of these agents for imaging CA IX in vivo gave variable performance; however, a number of agents proved very capable. As molecular imaging has become indispensable in current medical practice we anticipate that the clinical significance of CA IX will see continued development and improvements in imaging agents for targeting this enzyme.

Carbonic anhydrase IX as an imaging and therapeutic target for tumors and metastases

Carbonic anhydrase IX (CAIX) which is a zinc containing metalloprotein, efficiently catalyzes the reversible hydration of carbon dioxide. It is constitutively up-regulated in several cancer types and has an important role in tumor progression, acidification and metastasis. High expression of CAIX generally correlates with poor prognosis and is related to a decrease in the disease-free interval following successful therapy. Therefore, it is considered as a prognostic indicator in oncology.In this review, we describe CAIX regulation and its role in tumor hypoxia, acidification and metastasis. In addition, the molecular imaging of CAIX and its potential for use in cancer detection, diagnosis, staging, and for use in following therapy response is discussed. Both antibodies and small molecular weight compounds have been used for targeted imaging of CAIX expression. The use of CAIX expression as an attractive and promising candidate marker for systemic anticancer therapy is also discussed.

'Image and treat': an individualized approach to urological tumors

PURPOSE OF REVIEW

The current treatment options for advanced urologic cancers demonstrate limited efficacy. To obtain optimal clinical results, there is a need for new, individualized, therapeutic strategies, which have only recently been applied to these malignancies. Nuclear medicine plays an important role in establishing imaging biomarkers necessary for personalized medicine. This review focuses on the current status of the 'image and treat' approach combining molecular imaging with targeted radionuclide therapy of urological malignancies

RECENT FINDINGS

Tumor-specific targets in uro-oncology are showing promising results for development of personalized therapy using positron emission tomography/computed tomography (PET/CT) molecular imaging and radioimmunotherapy. The antibody cG250, which binds to carbonic anhydrase IX, is being evaluated as a radiolabeled imaging and therapeutic agent in clear-cell renal cell carcinoma. I-cG250 PET/CT has demonstrated excellent targeting of clear-cell renal cell carcinoma. Prostate-specific membrane antigen is a promising target for both PET/CT and radioimmunotherapy of prostate cancer. HER2 may be another potential target in bladder and prostate cancer.

SUMMARY

Tumor-specific targets and biomarkers are being studied for PET/CT and radioimmunotherapy. This may lead to development of new therapeutic strategies. However, considerable investment in new research will be required for personalized medicine to be routinely used in uro-oncology.

Unique biological properties of catalytic domain directed human anti-CAIX antibodies discovered through phage-display technology

Carbonic anhydrase IX (CAIX, gene G250/MN-encoded transmembrane protein) is highly expressed in various human epithelial tumors such as renal clear cell carcinoma (RCC), but absent from the corresponding normal tissues. Besides the CA signal transduction activity, CAIX may serve as a biomarker in early stages of oncogenesis and also as a reliable marker of hypoxia, which is associated with tumor resistance to chemotherapy and radiotherapy. Although results from preclinical and clinical studies have shown CAIX as a promising target for detection and therapy for RCC, only a limited number of murine monoclonal antibodies (mAbs) and one humanized mAb are available for clinical testing and development. In this study, paramagnetic proteoliposomes of CAIX (CAIX-PMPLs) were constructed and used for anti-CAIX antibody selection from our 27 billion human single-chain antibody (scFv) phage display libraries. A panel of thirteen human scFvs that specifically recognize CAIX expressed on cell surface was identified, epitope mapped primarily to the CA domain, and affinity-binding constants (KD) determined. These human anti-CAIX mAbs are diverse in their functions including induction of surface CAIX internalization into endosomes and inhibition of the carbonic anhydrase activity, the latter being a unique feature that has not been previously reported for anti-CAIX antibodies. These human anti-CAIX antibodies are important reagents for development of new immunotherapies and diagnostic tools for RCC treatment as well as extending our knowledge on the basic structure-function relationships of the CAIX molecule.

RLIP76: a target for kidney cancer therapy

RLIP76 is a multifunctional transporter protein that serves as an energy-dependent efflux mechanism for endogenously generated toxic metabolites as well as exogenous toxins, including chemotherapy drugs. Our recent studies in cultured cells, syngeneic animal tumor model, and in xenograft model have shown that RLIP76 serves a major cancer-specific antiapoptotic role in a wide variety of histologic types of cancer, including leukemia, melanoma, colon, lung, prostate, and ovarian cancer. Results of present studies in cell culture and xenograft model of Caki-2 cells show that RLIP76 is an important anticancer for kidney cancer because inhibition of RLIP76 function by antibody or its depletion by small interfering RNA or antisense DNA caused marked and sustained regression of established human kidney xenografts of Caki-2 cells in nude mouse.

Molecular aspects of tumour hypoxia

Hypoxia is an important feature of the microenvironment of a wide range of solid tumours. Its critical role in radio- and chemoresistance and its significance as an adverse prognostic factor have been well established over the last decades. On a cellular level, hypoxia evokes a complex molecular response with a central role for the HIF-1 pathway. The cellular processes under control of HIF-1 contain important prognostic information and comprise potential candidates for directing hypoxia-modifying therapies. This review will provide an overview of the current knowledge on the molecular aspects of tumour hypoxia and the link to clinical practice.