Construction, expression and tumor targeting of a single-chain Fv against human colorectal carcinoma

Discovery and characterization of a functional scFv for CCR2 inhibition via an extracellular loop

The chemokine receptor CCR2 plays a key role in cellular migration and inflammatory processes. While tremendous progress has been made in elucidating CCR2 function and inhibition, the majority of approaches target its N-terminal domain and less is known about the function of the remaining extracellular loops and their potential as targets. Here, we used phage display to identify an antibody-derived scFv (single chain variable fragment) clone that specifically targets the second extracellular epitope of CCR2 (ECL2) for inhibition. Using in silico molecular docking, we identified six potential primary binding conformations of the novel scFv to the specified CCR2 epitope. In silico molecular dynamic analysis was used to determine conformational stability and identify protein-protein interactions. Umbrella sampling of a range of configurations with incrementally increasing separation of scFv and target generated by force pulling simulations was used to calculate binding energies. Downstream characterization by ELISA showed high binding affinity of the ECL2-scFv to CCR2. Furthermore, we showed that blocking the second extracellular loop inhibits macrophage migration and polarized macrophages towards M1 inflammatory cytokine production as potently as lipopolysaccharide (LPS). These studies highlight the applicability of epitope-specific targeting, emphasize the importance of in silico predictive modeling, and warrant further investigation into the role of the remaining epitopes of CCR2.

An EGF receptor targeting Ranpirnase-diabody fusion protein mediates potent antitumour activity in vitro and in vivo

Cytotoxic ribonucleases such as the leopard frog derivative Ranpirnase (Onconase(®)) have emerged as a valuable new class of cancer therapeutics. Clinical trials employing single agent Ranpirnase in cancer patients have demonstrated significant clinical activity and surprisingly low immunogenicity. However, dose-limiting toxicity due to unspecific uptake of the RNase into non-cancerous cells is reached at relatively low concentrations of > 1 mg/m(2). We have in the present study generated a dimeric anti-EGFR Ranpirnase-diabody fusion protein capable to deliver two Ranpirnase moieties per molecule to EGFR-positive tumour cells. We show that this compound mediated far superior efficacy for killing EGFR-positive tumour cells than a monomeric counterpart. Most importantly, cell killing was restricted to EGFR-positive target cells and no dose-limiting toxicity of Ranpirnase-diabody was observed in mice. These data indicate that by targeted delivery of Ranpirnase non-selective toxicity can be abolished and suggests Ranpirnase-diabody as a promising new drug for therapeutic interventions in EGFR-positive cancers.

Analysis of the relationship between end-to-end distance and activity of single-chain antibody against colorectal carcinoma

We investigated the relationship of End-to-end distance between VH and VL with different peptide linkers and the activity of single-chain antibodies by computer-aided simulation. First, we developed (G4S)n (where n = 1-9) as the linker to connect VH and VL, and estimated the 3D structure of single-chain Fv antibody (scFv) by homologous modeling. After molecular models were evaluated and optimized, the coordinate system of every protein was built and unified into one coordinate system, and End-to-end distances calculated using 3D space coordinates. After expression and purification of scFv-n with (G4S)n as n = 1, 3, 5, 7 or 9, the immunoreactivity of purified ND-1 scFv-n was determined by ELISA. A multi-factorial relationship model was employed to analyze the structural factors affecting scFv: rn=ABn-ABO2+CDn-CDO2+BCn-BCst2. The relationship between immunoreactivity and r-values revealed that fusion protein structure approached the desired state when the r-value = 3. The immunoreactivity declined as the r-value increased, but when the r-value exceeded a certain threshold, it stabilized. We used a linear relationship to analyze structural factors affecting scFv immunoreactivity.

Radiation-guided P-selectin antibody targeted to lung cancer

PURPOSE

P-selectin expression is significantly increased in tumor microvasculature following exposure to ionizing radiation. The purpose of this study was to image radiation-induced P-selectin expression in vivo using optical imaging and gamma camera imaging in a heterotopic lung cancer model by using ScFv antibodies to P-selectin.

PROCEDURES

In vitro studies using endothelial cells were done using 3 Gy radiation and selected ScFv antibodies to P-selectin. In vivo studies were performed using Lewis lung carcinoma cells subcutaneously injected into the hind limbs of nude mice. Mice were treated with 6 Gy radiation and sham radiation 10 days post-inoculation. P-selectin expression was assessed with near-infrared imaging using Cy7 labeled antibody, and gamma camera imaging using( 111)In-DTPA labeled antibody.

RESULTS

In vitro studies showed antibody binding to P-selectin in radiation treated endothelial cells. In vivo optical imaging and gamma camera imaging studies showed significant tumor-specific binding to P-selectin in irradiated tumors compared to unirradiated tumors.

CONCLUSIONS

Optical imaging and gamma camera imaging are effective methods for visualizing in vivo targeting of radiation-induced P-selectin in lung tumors. This study suggests that fluorescent-labeled and radiolabeled ScFv antibodies can be used to target radiation-induced P-selectin for the tumor-specific delivery of therapeutic drugs and radionuclides in vivo.

Antibody constructs in cancer therapy

Whereas over 85% of human cancers are solid tumors, of the 8 monoclonal antibodies (mAbs) currently approved for cancer therapy, 25% are directed at solid tumor surface antigens (Ags). This shortfall may be due to barriers to achieving adequate exposure in solid tumors. Advancements in tumor biology, protein engineering, and theoretical modeling of macromolecular transport are currently enabling identification of critical physical properties for antitumor Abs. It is now possible to structurally modify Abs or even replace full Abs with a plethora of Ab constructs. These constructs include Fab and Fab'(2) fragments, scFvs, multivalent scFvs (e.g., diabodies and tribodies), minibodies (e.g., scFv-CH3 dimers), bispecific Abs, and camel variable functional heavy chain domains. The purpose of the article is to provide investigators with a conceptual framework for exploiting the recent scientific advancements. The focus is on 2 properties that govern tumor exposure: 1) physical properties that enable penetration of and retention by tumors, and 2) favorable plasma pharmacokinetics. It is demonstrated that manipulating molecular size, charge, valence, and binding affinity can optimize these properties. These manipulations hold the key to promoting tumor exposure and to ultimately creating successful Ab therapies for solid tumors.

Radioimmunotherapy with engineered antibodies

Although the advent of monoclonal antibody technology in the 1970s provided the means to specifically target radioisotopes to tumours, the initial clinical evaluations of radioimmunotherapy (RAIT) were largely unsuccessful. Over the past few decades, molecular biology techniques have advanced sufficiently to allow scientists to re-engineer antibodies to address the factors that were believed to be responsible for the failures of the early radioimmunotherapy trials. This review addresses the recent advances in antibody engineering and in RAIT strategies that have brought this field to the brink of success.

Comparative evaluation of immune response after laparoscopical and open total mesorectal excisions with anal sphincter preservation in patients with rectal cancer

AIM: The study of immune response of open versus laparoscopical total mesorectal excision with anal sphincter preservation in patients with rectal cancer has not been reported yet. The dissected retroperitoneal area that contacts directly with carbon dioxide is extensive in laparoscopic total mesorectal excision with anal sphincter preservation surgery. It is important to clarify whether the immune response of laparoscopic total mesorectal excision with anal sphincter preservation (LTME with ASP) in patients with rectal cancer is suppressed more severely than that of open surgery (OTME with ASP). This study was designed to compare the immune functions after laparoscopic and open total mesorectal excision with anal sphincter preservation for rectal cancer.

METHODS: This study involved 45 patients undergoing laparoscopic (n = 20) and open (n = 25) total mesorectal excisions with anal sphincter preservation for rectal cancer. Serum interleukin-2 (IL-2), interleukin-6 (IL-6), tumor necrosis factor α (TNF_α) were assayed preoperatively and on days 1 and 5 postoperatively. CD3⁺ and CD56⁺ T lymphocyte count, CD3^- and CD56⁺ natural killer cell (NK) count and immunoglobulin (IgG/IgM/IgA) were assayed preoperatively and on day 5 postoperatively. The numbers of CD3⁺ and CD56⁺ T lymphocytes and CD3^- and CD56⁺ NK cells were counted using flow cytometry. An enzyme-linked immunosorbent assay (ELISA) was used for IL-2, IL-6 and TNF_α determination. And IgG, IgM, and IgA were assayed using immunonephelometry.

RESULTS: The demographic data of the two groups had no difference. The preoperative levels of CD3⁺ and CD56⁺ T lymphocyte count, CD3^- and CD56⁺ NK count, serum IgG, IgM, IgA, IL-2, IL-6 and TNF_α also had no significant difference in the two groups (P > 0.05). The CD3⁺ and CD56⁺ T lymphocyte counts had no obvious changes after surgery in laparoscopic (d = -0.79% ± 3.83%) and open (d = 0.42% ± 2.09%) groups. The CD3^- and CD56⁺ NK counts were decreased postoperatively in both laparoscopic (d = -7.23% ± 11.33%) and open (d = -9.21% ± 13.93%) groups. The differences of the determined values of serum IgG, IgM and IgA on the fifth day after operation subtracted those before operation were -2.56 ± 2.14 g/L, -252.35 ± 392.94 mg/L, -506.15 ± 912.24 mg/L in laparoscopic group, and -1.81 ± 2.10 g/L, -282.72 ± 356.75 mg/L, -252.20 ± 396.28 mg/L in open group, respectively. The levels of IL-2 were decreased after operation in both groups. However, the levels of IL-6 were decreased after laparoscopic surgery (d₁ = -23.14 ± 263.97 ng/L and d₅ = -40.08 ± 272.03 ng/L), and increased after open surgery (d₁ = 27.38 ± 129.14 ng/L and d₅ = 21.67 ± 234.31 ng/L). The TNF_α levels were not elevated after surgery in both groups. There were no significant differences in the numbers of CD3⁺ and CD56⁺ T lymphocytes and CD3^- and CD56⁺ NK cells, the levels of IgG, IgM, IgA, IL-2, IL-6 and TNF_α between the two groups (P > 0.05).

CONCLUSION: There are no differences in immune responses between the patients having laparoscopic total mesorectal excision with anal sphincter preservation and those undergone open surgery for rectal cancer.

Expression of PCNA and CD44mRNA in colorectal cancer with venous invasion and its relationship to liver metastasis

AIM: To investigate the expression of proliferating cell nuclear antigen (PCNA) and CD44mRNA in colorectal cancer with venous invasion and its relationship with liver metastasis.

METHODS: Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect the expression of PCNA and CD44mRNA in 31 cases of colorectal cancer with venous invasion.

RESULTS: Positive expression rates of PCNA and CD44mRNA in colorectal cancer were higher than those without liver metastasis (P < 0.05 and P < 0.01). In case of colorectal cancer with liver metastasis, strongly positive rates of PCNA and CD44mRNA were 94.1% and 70.6%, respectively, significantly higher than those without liver metastasis. There was a positive relationship between the expressions of PCNA and CD44mRNA (r = 0.67, P < 0.05).

CONCLUSION: Detection of PCNA and CD44mRNA expression in colorectal cancer may be useful for evaluating liver metastasis of cancer cells.