Antitumor effect of MAb EMD 55900 depends on EGF-R expression and histopathology

Increased plasma colloid osmotic pressure facilitates the uptake of therapeutic macromolecules in a xenograft tumor model

Elevated tumor interstitial fluid pressure (TIFP) is a characteristic of most solid tumors. Clinically, TIFP may hamper the uptake of chemotherapeutic drugs into the tumor tissue reducing their therapeutic efficacy. In this study, a means of modulating TIFP to increase the flux of macromolecules into tumor tissue is presented, which is based on the rationale that elevated plasma colloid osmotic pressure (COP) pulls water from tumor interstitium lowering the TIFP. Concentrated human serum albumin (20% HSA), used as an agent to enhance COP, reduced the TIFP time-dependently from 8 to 2 mm Hg in human tumor xenograft models bearing A431 epidermoid vulva carcinomas. To evaluate whether this reduction facilitates the uptake of macromolecules, the intratumoral distribution of fluorescently conjugated dextrans (2.5 mg/ml) and cetuximab (2.0 mg/ml) was probed using novel time domain nearinfrared fluorescence imaging. This method permitted discrimination and semiquantification of tumor-accumulated conjugate from background and unspecific probe fluorescence. The coadministration of 20% HSA together with either dextrans or cetuximab was found to lower the TIFP significantly and increase the concentration of the substances within the tumor tissue in comparison to control tumors. Furthermore, combined administration of 20% HSA plus cetuximab reduced the tumor growth significantly in comparison to standard cetuximab treatment. These data demonstrate that increased COP lowers the TIFP within hours and increases the uptake of therapeutic macromolecules into the tumor interstitium leading to reduced tumor growth. This model represents a novel approach to facilitate the delivery of therapeutics into tumor tissue, particularly monoclonal antibodies.

EGF-R and Her2/neu overexpressing tumors: independent collectives for treatment of breast cancer by specific monoclonal antibody-therapy

PURPOSE

In our recent studies, we demonstrated that breast cancer treatment by anti-EGF-R antibody resulted in a significant therapeutic effect in vivo. Furthermore, we were able to elucidate histopathologic parameters with an impact on therapy success. The aim of this study was the evaluation of EGF-R and Her2/neu protein expression on a large series of primary breast cancer, to elucidate if anti-EGF-R antibody therapy is a new therapeutic option for patients who are Her2/neu negative and where, therefore, anti-Her2/neu antibody treatment is not applicable.

METHODS

We analyzed EGF-R and Her2/neu protein expression of 149 consecutive primary breast cancer specimens by fully quantitative enzyme-linked immunosorbent assay. For evaluation of stochastic independence, we used chi(2)-test as goodness-of-fit test.

RESULTS

We found EGF-R and Her2/neu expression as stochastically independent in primary breast cancer.

CONCLUSIONS

Anti-EGF-R antibody treatment is a potential therapeutic option for patients with Her2/neu negative breast cancer.

Anti-epidermal growth factor receptor-antibody therapy for treatment of breast cancer

Recent studies demonstrated that tumors overexpressing the epidermal growth factor receptor (EGF-R, erbB-1) are associated with poor clinical outcome. This led to the development of a variety of monoclonal antibodies targeting the extracellular domain of this receptor tyrosine kinase. The aim of our study was the evaluation of anti-EGF-R antibody EMD 55900 therapy for treatment of breast cancer. On the basis of 299 tumor specimens derived from breast cancer patients, we investigated EGF-R expression and generated a collective of primary xenotransplants in athymic nude mice. The animals received therapy in 2 treatment schedules to investigate the therapeutic response in early stages of tumor formation as well as on well established tumors. Using 6 different tumors with EGF-R expression levels between 10-300 fmol/mg total protein, we found a therapeutic effect when the EGF-R expression of the tumors was at least 40 fMol/mg. On the basis of these experimental data and our EGF-R expression analysis of breast cancer specimens, we conclude that up to 15% of breast cancer patients could benefit from this monotherapy with EMD 55900.