Selective Gene Therapy for Prostate Cancer Cells Using Liposomes Conjugated with IgM Type Monoclonal Antibody against Prostate-Specific Membrane Antigen

Nanoparticles for Targeting of Prostate Cancer

Prostate cancer (PCa) is the leading cause of death by cancer in men. Because of the drastic decline in the survival rate of PCa patients with advanced/metastatic disease, early diagnosis of disease and therapy without toxic side effects is crucial. Chemotherapy is widely used to control the progression of PCa at the later stages; however, it is associated with off-target toxicities and severe adverse effects due to the lack of specificity. Delivery of therapeutic or diagnostic agents by using targeted nanoparticles is a promising strategy to enhance accuracy and sensitivity of diagnosis of PCa and to increase efficacy and specificity of therapeutic agents. Numerous efforts have been made in past decades to create nanoparticles with different architectural bases for specific delivery payloads to prostate tumors. Major PCa associated cell membrane protein markers identified as targets for such purposes include folate receptor, sigma receptors, transferrin receptor, gastrin-releasing peptide receptor, urokinase plasminogen activator receptor, and prostate specific membrane antigen. Among these markers, prostate specific membrane antigen has emerged as an extremely specific and sensitive targetable marker for designing targeted nanoparticle-based delivery systems for PCa. In this article, we review contemporary advances in design, specificity, and efficacy of nanoparticles functionalized against PCa. Whenever feasible, both diagnostic as well as therapeutic applications are discussed.

Production and characterization of monoclonal antibodies against recombinant extracellular domain of CD99

BACKGROUND AND OBJECTIVE

CD99/MIC2 gene product is a heavily glycosylated transmembrane protein which plays a major role in homotypic cell adhesion, apoptosis of double positive T cells and vesicular protein trafficking. It is over expressed in various cancers and has been considered as an ideal therapeutic target. The present study focused at developing monoclonal antibodies against the extracellular domain (ECD) of CD99 using hybridoma technology.

MATERIALS AND METHODS

In order to generate monoclonal antibodies, the recombinant ECD of CD99 was used for immunizing the mice. Resulting hybridomas were screened through indirect ELISA. Clones which gave high absorbance values were sub cloned by limiting dilution followed by isotype determination, IP, WB and FACS. The monoclonal antibody 547F2 4F12 was purified from culture supernatant using FPLC and further screened using IF. Finally, the antibodies were validated for specificity using siRNA knock-down.

RESULTS

We were able to establish stable hybridoma clones secreting CD99 antibodies. The antibodies reacted with both the recombinant ECD as well as the wild type CD99 and their isotype's were determined as IgM.

CONCLUSION

Based on these results, we propose that the purified monoclonal antibody 547F2 4F12 could be possibly used for targeting tumors which over express CD99.

Selective suicide gene therapy of colon cancer cell lines exploiting fibroblast growth factor 18 promoter

Fibroblast growth factor 18 (FGF18) is one of the genes downstream of Wnt, one of the most important signaling pathways activated in colon cancer. An FGF18 promoter containing a single T-cell factor/lymphocyte enhancing factor 1 (TCF/LEF1) binding site was inserted upstream of a thymidine kinase (TK) suicide gene module, while a bacterial beta-Gal (LacZ) element served as the reporter gene. Following transient transfection with pUCFGF18LacZ, beta-Gal staining showed that 5% of SW480, 10% of HCT116, 0% of human umbilical vein endothelial cells (HUVECs) and 0% of normal colon cells (NCCs) had expressed LacZ. beta-Gal enzyme-linked immunosorbent assay revealed that the ratio of pUCFGF18LacZ activity to that of positive control was 0.09 and 0.25 in SW480 and HCT116, respectively (significantly higher than mock plasmid), while there were no significant changes in the beta-Gal expression in HUVEC and NCC cells transfected with pUCFGF18LacZ or mock plasmid. Following transfection with pUCFGF18TK and pUCCMVTK (positive control), cytotoxicity analysis of transfected cells showed that treatment with ganciclovir (GCV) significantly decreased SW480 and HCT116 cell survival at GCV concentrations above 20 microg/mL. An inverse correlation between GCV concentration and cell viability was evident in both colon cancer cell lines following transfection with these suicide plasmids. pUCFGF18TK and pUCCMVTK induced apoptosis after the administration of GCV in HCT116, but not in SW480, as demonstrated by M30 cytodeath antibody. This discrepancy may stem from differences in the mechanisms of TK/GCV-induced apoptosis in p53-proficient (HCT116) and -deficient (SW480) cells. The specific activity of the FGF18 promoter in HCT116 and SW480 may reflect the advantage of this promoter over artificial promoters containing artificial TCF/LEF binding sites.

Selective suicide gene therapy of colon cancer exploiting the urokinase plasminogen activator receptor promoter

Colon cancer is the third and fourth most prevalent cancer among Iranian men and women, respectively. Suicide gene therapy is one of the alternative therapeutic modalities for cancer. The application of specific promoters for therapeutic genes should decrease the adverse effects of this modality. The combined aims of this study were to design a specific suicide gene therapy construct for colon cancer and study its effect in distinct representatives of transformed and nontransformed cells. The KRAS oncogene signaling pathway is one of the most important signaling pathways activated in colon cancer; therefore, we inserted the urokinase plasminogen activator receptor (uPAR; PLAUR gene) promoter as one of the upregulated promoters by this pathway upstream of a suicide gene (thymidine kinase [TK]) and a reporter gene (beta-galactosidase, beta-gal [LacZ]). This promoter is a natural combination of different motifs responsive to the RAS signaling pathway, such as the transcription factors AP1 (FOS/JUN), SP1, SP3, and AP2alpha, and nuclear factor kappa B (NFkappaB). The reporter plasmid under the control of the uPAR promoter (PUCUPARLacZ) had the ability to express beta-gal in colon cancer cells (human colon adenocarcinoma [SW480] and human colorectal carcinoma [HCT116] cell lines), while it could not express beta-gal in nontransformed human umbilical vein endothelial cells (HUVEC) and normal colon cells. After confirming the ability of pUCUPARTK (suicide plasmid) to express TK in SW480 and HCT116 cells by real-time PCR, cytotoxicity assays showed that pUCUPARTK decreased the viability of these cells in the presence of ganciclovir 20 and 40 microg/mL (and higher), respectively. Although M30 CytoDEATH antibody could not detect a significant rate of apoptosis induced by ganciclovir in pUCUPARTK-transfected HCT116 cells, the percentage of stained cells was marked in comparison with untreated cells. While this antibody could detect apoptosis in HCT116 cell line transfected with positive control plasmid, it could not detect apoptosis in SW480 cells transfected with the same positive control. This discrepancy could be attributed to the different mechanisms of TK/ganciclovir-induced apoptosis in tumor protein p53 (TP53)-expressing (HCT116) and -deficient (SW480) cells. Annexin-propidium iodide staining could detect apoptosis in treated, pUCUPARTK-transfected SW480 and HCT116 cells. This study showed that the uPAR promoter can be considered as a suitable candidate for specific suicide gene therapy of colon cancer and probably other cancers in which the RAS signaling pathway is involved in their carcinogenesis process.

Gene therapy via inducible nitric oxide synthase: a tool for the treatment of a diverse range of pathological conditions

Nitric oxide (NO(.)) is a reactive nitrogen radical produced by the NO synthase (NOS) enzymes; it affects a plethora of downstream physiological and pathological processes. The past two decades have seen an explosion in the understanding of the role of NO(.) biology, highlighting various protective and damaging modes of action. Much of the controversy surrounding the role of NO(.) relates to the differing concentrations generated by the three isoforms of NOS. Both calcium-dependent isoforms of the enzyme (endothelial and neuronal NOS) generate low-nanomolar/picomolar concentrations of NO(.). By contrast, the calcium-independent isoform (inducible NOS (iNOS)) generates high concentrations of NO(.), 2-3 orders of magnitude greater. This review summarizes the current literature in relation to iNOS gene therapy for the therapeutic benefit of various pathological conditions, including various states of vascular disease, wound healing, erectile dysfunction, renal dysfunction and oncology. The available data provide convincing evidence that manipulation of endogenous NO(.) using iNOS gene therapy can provide the basis for future clinical trials.

Synergistic Value of Single-Photon Emission Computed Tomography/Computed Tomography Fusion to Radioimmunoscintigraphic Imaging of Prostate Cancer

The rationale on which positron emission tomography/computed tomography (PET/CT) imaging is based, combining the functional features of PET with the anatomic detail of CT, provides many advantages that are easily transferable to single-photon emission computed tomography (SPECT)/CT imaging. Our efforts have focused on applying fused SPECT/CT imaging to identify prostate cancer and its metastasis and recurrence through radioimmunoscintigraphy (RIS). This application of RIS to imaging prostate cancer requires 2 key components: (1) a well-defined target associated with the cancer and (2) a "magic bullet" to seek that target. A well-characterized RIS target for prostate cancer is prostate-specific membrane antigen, or PSMA, and finding the bullet to seek this target with high sensitivity and specificity has been the focus of intensive study for nearly two decades. One of the candidate bullets developed is capromab pendetide, which is a monoclonal antibody that seeks PSMA. This antibody is commercially available as ProstaScint, which can be labeled with indium-111 to localize prostate cancer via SPECT imaging. In the course of applying fused SPECT/CT ProstaScint imaging to more than 800 prostate cancer cases, numerous refinements to our protocol have evolved that are aimed at staging the cancer with utmost accuracy. In addition to optimizing the localization of prostate cancer and its metastasis, these refinements also have been extended toward guiding both the implantation of radioactive seeds in brachytherapy and in other types of radiation therapy which is illustrated through 5 case reports. Progress in the therapeutic targeting of PSMA is also being actively explored, which has more universal ramifications because PSMA is found in the neovasculature of other types of cancers.