Tumor uptake of intravenously administered radiolabeled antibodies in ovarian carcinoma patients in relation to antigen expression and other tumor characteristics

Comparative evaluation of bolus and fractionated administration modalities for two antibody-cytokine fusions in immunocompetent tumor-bearing mice

Antibody-cytokine fusion proteins are being considered as biopharmaceuticals for cancer immunotherapy. Tumor-homing cytokine fusions typically display an improved therapeutic activity compared to the corresponding unmodified cytokine products, but toxicity profiles at equivalent doses are similar, since side effects are mainly driven by the cytokine concentration in blood. In order to explore avenues to harness the therapeutic potential of antibody-cytokine fusions while decreasing potential toxicity, we compared bolus and fractionated administration modalities for two tumor-targeting antibody-cytokine fusion proteins based on human interleukin-2 (IL2) and murine tumor necrosis factor (TNF) (i.e., L19-hIL2 and L19-mTNF) in two murine immunocompetent mouse models of cancer (F9 and C51). A comparative quantitative biodistribution analysis with radio-labeled protein preparations revealed that a fractionated administration of L19-hIL2 could deliver comparable product doses to the tumor with decreased product concentration in blood and normal organs, compared to bolus injection. By contrast, L19-mTNF (a product that causes a selective vascular shutdown in the tumor) accumulated most efficiently after bolus injection. Fractionated schedules allowed the safe administration of a cumulative dose of L19-mTNF, which was 2.5-times higher than the lethal dose for bolus injection. Dose fractionation led to a prolonged tumor growth inhibition for F9 teratocarcinomas, but not for C51 colorectal tumors, which responded best to bolus injection. Thus, dose fractionation may have different outcomes for the same antibody-cytokine product in different biological contexts.

Relationship between immunohistochemical staining extent of CD47 and histopathologic features of bladder tumor

Introduction

It has been shown that CD47 is an important diagnostic and prognostic marker in many cancer types. However, the relationship between CD47 and bladder tumor stage has not been shown in previous studies. To the best of our knowledge, this is the first study investigating the association of CD47 with stages of bladder cancer.

Material and methods

Surgical specimens of 175 patients were included in the study. The CD47 staining assessment was performed in the following categories; none, focal, moderate and diffuse. The statistics of the study were tested using t-test and analysis of variance.

Results

We demonstrated much less CD47 staining extent in Ta tumor pathology compared to T1 and T1+T2+T3+T4 tumor pathology (p = 0.034 and p = 0.016, respectively). We also showed that the average value of CD47 staining extent with CIS+ was significantly higher compared to CIS- among NMIBC (p = 0.0248). However, no significant differences in CD47 staining pattern were observed in the following study groups: high vs. low-grade tumors in non-muscle invasive bladder cancer (NMIBC); MIBC (T2-T4) vs. NMIBC; lymph node involvement (N1-N3) vs. non-lymph node involvement (N0) in MIBC (T2-T4).

Conclusions

Our study demonstrated that CD47 might have a critical role in the progression of Ta to T1 stage. Furthermore, we showed that CD47 is highly expressed in CIS+ NMIBC compared to CIS- NMIBC. Thus, differentiating stages with the help of this new potential marker may help clinicians treat bladder tumors better. Future studies to determine the role of CD47 on pathophysiology, diagnosis and prognosis of bladder tumor are warranted.

Therapeutic opportunities for targeting the ubiquitous cell surface receptor CD47

INTRODUCTION

CD47 is a ubiquitously expressed cell surface receptor that serves as a counter-receptor for SIRPα in recognition of self by the innate immune system. Independently, CD47 also functions as an important signaling receptor for regulating cell responses to stress.

AREAS COVERED

We review the expression, molecular interactions, and pathophysiological functions of CD47 in the cardiovascular and immune systems. CD47 was first identified as a potential tumor marker, and we examine recent evidence that its dysregulation contributes to cancer progression and evasion of anti-tumor immunity. We further discuss therapeutic strategies for enhancing or inhibiting CD47 signaling and applications of such agents in preclinical models of ischemia and ischemia/reperfusion injuries, organ transplantation, pulmonary hypertension, radioprotection, and cancer.

EXPERT OPINION

Ongoing studies are revealing a central role of CD47 for conveying signals from the extracellular microenvironment that limit cell and tissue survival upon exposure to various types of stress. Based on this key function, therapeutics targeting CD47 or its ligands thrombospondin-1 and SIRPα could have broad applications spanning reconstructive surgery, engineering of tissues and biocompatible surfaces, vascular diseases, diabetes, organ transplantation, radiation injuries, inflammatory diseases, and cancer.

Immunohistochemical analysis of intratumoral heterogeneity of [131I]cG250 antibody uptake in primary renal cell carcinomas

In previous studies, highly heterogeneous uptake of 131I-labelled chimeric monoclonal antibody G250 ([131I]cG250) in primary renal cell carcinomas has been observed (intratumoral differences > factor 100). In this study, we investigated a possible correlation between intratumoral antibody uptake and four immunohistochemically determined parameters: G250 antigen expression, blood vessel density, neovascularization and percentage of viable tumour cells. Whole tumour slices of four different tumours were cut into 1-cm3 cubes, and in each cube the [131I]cG250 uptake was determined. The correlation between [131I]cG250 uptake and each individual parameter was determined in a multiple regression analysis. Additionally, the data were reanalysed after introducing arbitrary cut-off values for each parameter. If a sample showed expression of a parameter above the introduced threshold value, this sample fulfilled one condition. Subsequently, the Pearson correlation coefficients were calculated from [131I]cG250 uptake and the number of fulfilled conditions (0-3). All tumour samples with high [131I]cG250 uptake [> 0.1% of the injected dose per gram (ID g(-1))] showed high antigen expression (> 50%). However, not all samples with high antigen expression displayed high uptake. A statistically significant correlation between [131I]cG250 uptake and antigen expression was found (beta = 0.44, 0.69 and 0.74) in three out of four tumours analysed. Of the other determined parameters, no consistent correlation with [131I]cG250 uptake was found; only the percentage of viable tumour cells correlated significantly in two out of four tumours (beta = 0.80 and 0.26). Calculation of the Pearson correlation coefficients showed a statistically significant correlation between [131I]cG250 uptake and an increased number of fulfilled conditions in all tumours, indicating that each of the individual parameters contribute to the uptake of [131I]cG250. These observations indicate that high antigen expression is a prerequisite for high antibody uptake. However, regional differences in antibody uptake within a tumour cannot be explained by antigen expression alone.

HPMA copolymer-anticancer drug-OV-TL16 antibody conjugates. II. Processing in epithelial ovarian carcinoma cells in vitro

The binding, internalization, subcellular trafficking and in vitro cytotoxicity of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-anti-cancer drug-OV-TL16 antibody (Ab) conjugates in the ovarian carcinoma OVCAR-3 cell line have been investigated. Adriamycin (ADR) and meso chlorin e6 mono(N-2-aminoethylamide) (Mce6) photosensitizer were used as anti-cancer drugs. Targeted (Ab-containing) conjugates were compared with non-targeted HPMA copolymer-drug conjugates and with free drugs. Targeted conjugates were taken up rapidly by cells and detected within lysosomes by confocal fluorescence microscopy. The ADR attached to polymer chains via a degradable GFLG spacer was released from the conjugate, diffused via the lysosomal membrane into the cytoplasm and ultimately accumulated in the cell nuclei. In contrast, conjugates containing ADR bound via the GG spacer accumulated in the lysosomes, but no fluorescence could be detected in the cell nuclei. Binding the drugs to a non-targeted HPMA copolymer decreased their cytotoxicity in vitro. The IC50 dose increased from 2 microM for free ADR to 150 microM for P(GFLG)-ADR (P is the HPMA copolymer backbone) and from 0.34 microM for free Mce6 (with light) to 290 microM for P-(GG)-Mce6. However, attachment of OV-TL16 Abs rendered HPMA copolymer-drug conjugates biorecognizable by OVCAR-3 cells and markedly increased their cytotoxicity. The IC50 doses were 4.4 and 0.38 microM for the targeted conjugates P(GFLG)-ADR-Ab and P(GG)-Mce6-Ab (with light), respectively. Biorecognition was shown to be specific by inhibition experiments with free Ab. The findings indicate the potential of these conjugates as effective agents in the treatment of ovarian cancer.

Selection of monoclonal antibody E48 IgG or U36 IgG for adjuvant radioimmunotherapy in head and neck cancer patients

Preliminary data from recent clinical radioimmunoscintigraphy studies indicate that 99mTc-labelled murine monoclonal antibodies (MAbs) E48 and U36 have a similar ability to target squamous cell carcinoma of the head and neck (HNSCC) selectively. In the present study we describe additional aspects of murine and chimeric MAb (mMAb and cMAb) E48 and U36, which might influence the selection of one MAb for adjuvant radioimmunotherapy. To make direct comparison possible, ten patients received 11.2 +/- 0.3 and 11.1 +/- 0.2 mg (n = 5) or 51.1 +/- 0.1 and 51.0 +/- 0.4 mg (n = 5) of both mE48 IgG and mU36 IgG labelled with 131I and 125I simultaneously and underwent surgery 7-8 days after injection. The mean uptake of iodine-labelled mE48 IgG and mU36 was highest in tumour tissue, 8.9 +/- 8.9 and 8.2 +/- 4.4 %ID kg(-1) respectively. Tumour to non-tumour ratios for oral mucosa, skin, muscle, blood and bone marrow aspirate were 2.5, 5.5, 25.2, 4.7 and 4.0 respectively in the case of mE48 IgG and 2.3, 4.1, 21.0, 5.8 and 5.8 respectively in the case of mU36 IgG. The distribution of mMAbs E48 and U36 throughout tumours that had been collected in previous studies was heterogeneous when administered at a dose of 1 or 12 mg, and homogeneous when administered at a dose of 52 mg. Administration of mE48 IgG (1-52 mg) resulted in a human anti-mouse antibody response in 12 out of 28 patients, while for mU36 IgG (1-52 mg), this figure was three out of 18 patients. cMAb E48 was shown to be highly effective in mediating antibody-dependent cellular cytotoxicity in vitro, while cMAb U36 and mMAbs E48 and U36 were not effective at all. Rationales are provided that give priority to the start of adjuvant radioimmunotherapy trials with 186Re-labelled cMAb U36 IgG in head and neck cancer patients who are at high risk for the development of locoregional recurrences and distant metastases.