Epidermal growth factor receptor-targeted photosensitizer selectively inhibits EGFR signaling and induces targeted phototoxicity in ovarian cancer cells

Abstract

Targeted photosensitizer delivery to EGFR expressing cells was achieved in the present study using a high purity, targeted photoimmunoconjugate (PIC). When the PDT agent, benzoporphyin monoacid ring A (BPD) was coupled to an EGFR-targeting antibody (cetuximab), we observed altered cellular localization and selective phototoxicity of EGFR-positive cells, but no phototoxicity of EGFR-negative cells. Cetuximab in the PIC formulation blocked EGF-induced activation of the EGFR and downstream signaling pathways. Our results suggest that photoimmunotargeting is a useful dual strategy for the selective destruction of cancer cells and also exerts the receptor-blocking biological function of the antibody.

Selective treatment and monitoring of disseminated cancer micrometastases in vivo using dual-function, activatable immunoconjugates

“…We observed a trend in reduced number of EOC cells using Cet-BPD(1:7) in the absence of photoactivation (Fig. 5B), which indicates that Cet-BPD possesses similar anti-EGFR and antitumor activity to cetuximab monotherapy (12,36). NIR photoactivation for taPIT (two cycles) achieved a statistically significant mean reduction in tumor burden of 89% relative to untreated mice (Fig.…”

“…This quenching phenomenon increases the tumor specificity when optimally designed; however, excess BPD loading results in the loss of cancer cell-specific delivery. In a series of chemical synthesis and in vitro cell culture studies, we previously identified an optimal conjugation ratio of approximately seven BPD molecules per mAb molecule, Cet-BPD(1:7), as a strongly quenched (sevenfold) and cancer cell-specific construct (35) that retains the biological activity of cetuximab (36). These in vitro studies suggest that, like cetuximab, Cet-BPD is trafficked to lysosomes as part of the EGFR internalization and degradation pathway where more than one-half of the Cet-BPD immunoconjugates release BPD resulting in dequenching and activation of both BPD phototoxicity and fluorescence emission in cell culture (37).…”

“…taPIT holds potential to improve cancer survival by leveraging the distinct mechanisms of photodynamic action (13) to treat drug-resistant cells (26) and reverse chemoresistance (20), thereby reducing the number of cycles of chemotherapy needed to elicit tumor destruction (23). In addition, rationally designed immunoconjugates simultaneously inhibit treatment survival signaling pathways [e.g., the EGFR pathway (56)] in concert with their photocytotoxic effects (36). Molecular tumor targeting also provides opportunities for fluorescence-guided surgery (15)(16)(17) to remove more disease before taPIT and chemotherapy.…”

New Approaches to Photodynamic Therapy from Types I, II and III to Type IV Using One or More Photons

“…cetuximab) which bind to overexpressed enzymes or receptors in the neoplastic tissue or tumour vasculature [7,141,142]. Photoimmunotherapy using a NIR absorbing phthalocyanine (IR700) conjugated to monoclonal EGFRbinding antibodies triggered in vivo xenograft tumour shrinkage after irradiation with NIR light in EGFR overexpressing cells.…”

“…Benzoporphyrin derivative monoacid-A conjugated to cetuximab, an anti-EGFR antibody, changes the PS localization within EGFR-positive cells from mitochondria to lysosomes. No phototoxicity was observed in EGFRnegative cells [142]. When the same conjugate was additionally incorporated into Preformed Plain Liposomes to form so called photo-immuno-conjugate-associatingliposomes (PICAL) PDT induced cell killing of ovarian cancer cells was further enhanced [144].…”