Antibody-mediated blockade of integrin alpha v beta 6 inhibits tumor progression in vivo by a transforming growth factor-beta-regulated mechanism.

Department of Discovery Immunology, Biogen Idec, Cambridge, Massachusetts 02142, USA.
Cancer Research (Impact Factor: 9.28). 01/2008; 68(2):561-70. DOI: 10.1158/0008-5472.CAN-07-2307
Source: PubMed

ABSTRACT The alpha(v)beta(6) integrin is up-regulated on epithelial malignancies and has been implicated in various aspects of cancer progression. Immunohistochemical analysis of alpha(v)beta(6) expression in 10 human tumor types showed increased expression relative to normal tissues. Squamous carcinomas of the cervix, skin, esophagus, and head and neck exhibited the highest frequency of expression, with positive immunostaining in 92% (n = 46), 84% (n = 49), 68% (n = 56), and 64% (n = 100) of cases, respectively. We studied the role of alpha(v)beta(6) in Detroit 562 human pharyngeal carcinoma cells in vitro and in vivo. Prominent alpha(v)beta(6) expression was detected on tumor xenografts at the tumor-stroma interface resembling the expression on human head and neck carcinomas. Nonetheless, coculturing cells in vitro with matrix proteins did not up-regulate alpha(v)beta(6) expression. Detroit 562 cells showed alpha(v)beta(6)-dependent adhesion and activation of transforming growth factor-beta (TGF-beta) that was inhibited >90% with an alpha(v)beta(6) blocking antibody, 6.3G9. Although both recombinant soluble TGF-beta receptor type-II (rsTGF-beta RII-Fc) and 6.3G9 inhibited TGF-beta-mediated Smad2/3 phosphorylation in vitro, there was no effect on proliferation. Conversely, in vivo, 6.3G9 and rsTGF-beta RII-Fc inhibited xenograft tumor growth by 50% (n = 10, P < 0.05) and >90% (n = 10, P < 0.001), respectively, suggesting a role for the microenvironment in this response. However, stromal collagen and smooth muscle actin content in xenograft sections were unchanged with treatments. Although further studies are required to consolidate in vitro and in vivo results and define the mechanisms of tumor inhibition by alpha(v)beta(6) antibodies, our findings support a role for alpha(v)beta(6) in human cancer and underscore the therapeutic potential of function blocking alpha(v)beta(6) antibodies.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Incorporation of fluorine-18 ((18)F) into radiotracers by capturing ionic [(18)F]-species can greatly accelerate and simplify radiolabeling for this important positron emission tomography (PET) radioisotope. Among the different strategies, the incorporation of aluminum [(18)F]fluoride (Al[(18)F](2+)) into NOTA chelators has recently emerged as a robust approach to peptide radiolabeling. This study presents Al[(18)F](2+)-radiolabeling of an αvβ6 integrin-targeted peptide (NOTA-PEG28-A20FMDV2) and its in vitro and in vivo evaluation. Aluminum [(18)F]fluoride was prepared at r.t. from [(18)F]fluoride (40 MBq-11 GBq) and introduced into NOTA-PEG28-A20FMDV2 (1) in sodium acetate (pH 4.1; 100°C, 15 min). The radiotracer Al[(18)F] NOTA-PEG28-A20FMDV2 (2) was purified by HPLC, formulated in PBS and evaluated in vitro (stability; binding and internalization in αvβ6(+) and αvβ6(-) cells) and in vivo (paired αvβ6(+) and αvβ6(-) xenograft mice: PET/CT, biodistribution, tumor autoradiography and metabolites). The radiotracer 2 was prepared in 90±6 min (incl. formulation; n=3) in 19.3±5.4% decay corrected radiochemical yield (radiochemical purity: >99%; specific activity: 158±36 GBq/μmol) and was stable in PBS and serum (2 h). During in vitro cell binding studies, 2 showed high, αvβ6-targeted binding (αvβ6(+): 42.4±1.2% of total radioactivity, ratio (+)/(-)=8.4/1) and internalization (αvβ6(+): 28.3±0.5% of total radioactivity, (+)/(-)=11.7/1). In vivo, 2 maintained αvβ6-targeted binding (biodistribution; 1 h: αvβ6(+): 1.74±0.38% ID/g, (+)/(-)=2.72/1; 4 h: αvβ6(+): 1.21±0.56% ID/g, (+)/(-)=4.0/1; 11% intact 2 in tumor at 1 h), with highest uptake around the tumor edge (autoradiography). Most of the radioactivity cleared rapidly in the urine within one hour, but a significant fraction remained trapped in the kidneys (4 h: 229±44% ID/g). The Al[(18)F]/NOTA-based radiolabeling was rapid and efficient, and the radiotracer 2 showed good αvβ6-selectivity in vitro and in vivo. However, in contrast to A20FMDV2 labeled with covalently bound [(18)F]-prosthetic groups (e.g., [(18)F]fluorobenzoic acid), 2 demonstrated significant trapping in kidneys, similar to radiometal-labeled chelator-analogs of 2.
    Nuclear Medicine and Biology 01/2014; 41(1):43-50. · 2.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Integrin αvβ6 is an epithelially-restricted heterodimeric transmembrane glycoprotein, known to interact with the urokinase plasminogen activating receptor (uPAR), playing a critical role in cancer progression. While the X-ray crystallographic structures of segments of other integrin heterodimers are known, there is no structural information for the complete αvβ6 integrin to assess its direct interaction with uPAR. We have performed structural analysis of αvβ6•uPAR interactions using model data with docking simulations to pinpoint their interface, in accord with earlier reports of the β-propeller region of integrin α-chain interacting with uPAR. Interaction of αvβ6•uPAR was demonstrated by our previous study using immunoprecipitation coupled with proteomic analysis by mass spectrometry. Recently this interaction was validated with proximity ligation assays and peptide arrays. The data suggested that two potential peptide regions from domain II and one peptide region from domain III of uPAR, interact with αvβ6 integrin. Only the peptide region from domain III is consistent with the three-dimensional interaction site proposed in this study. The molecular basis of integrin αvβ6•uPAR binding using structural data is discussed for its implications as a potential therapeutic target in cancer management.
    Journal of Structural Biology 01/2014; · 3.36 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Integrin ανβ6 is highly expressed in a range of human cancers and frequently correlates with patient survival. This study examines correlations between ανβ6 expression and patient clinico-pathological features in Stage B and Stage C rectal cancer, including overall survival. Expression of ανβ6 was measured in 362 Stage B or C rectal cancer tissue samples at the tumour central region, invasive tumour front and adjacent non-neoplastic mucosa using immunohistochemistry. Distribution of ανβ6 was found to be significantly higher at the invasive front compared to central regions of the tumour (p<0.001) or adjacent non-neoplastic mucosa (p<0.001) suggesting ανβ6 plays a role in tumour cell invasion. However, integrin ανβ6 expression was not associated with clinico-pathological features or overall survival indicating it is not an independent prognostic marker differentiating Stage B or C rectal cancer. Previous ανβ6 studies have suggested the expression of ανβ6 is involved in the earlier stages (i.e. Stages A/B) of tumour progression rather than the later stages (i.e. Stages C/D). However, our study has revealed that in rectal cancer ανβ6 expression does not increase between Stages B and C, but may occur earlier, namely before or during Stage B cancer.
    PLoS ONE 01/2014; 9(5):e97248. · 3.53 Impact Factor