Reduction of Circulating Cancer Cells and Metastases in Breast-Cancer Models by a Potent EphA2-Agonistic Peptide–Drug Conjugate

Abstract

EphA2 overexpression has been associated with metastasis in multiple cancer types, including melanomas and ovarian, prostate, lung, and breast cancers. We have recently proposed the development of peptide-drug conjugates (PDCs) using agonistic EphA2-targeting agents, such as the YSA peptide or its optimized version, 123B9. Although our studies indicated that YSA- and 123B9-drug conjugates can selectively deliver cytotoxic drugs to cancer cells in vivo, the relatively low cellular agonistic activities (i.e., the high micromolar concentrations required) of the agents toward the EphA2 receptor remained a limiting factor to the further development of these PDCs in the clinic. Here, we report that a dimeric version of 123B9 can induce receptor activation at nanomolar concentrations. Furthermore, we demonstrated that the conjugation of dimeric 123B9 with paclitaxel is very effective at targeting circulating tumor cells and inhibiting lung metastasis in breast-cancer models. These studies represent an important step toward the development of effective EphA2-targeting PDCs.

Prostate Cancer Metastases Are Strongly Inhibited by Agonistic Epha2 Ligands in an Orthotopic Mouse Model

“…While both agents seemed very active, ephrinA1-Fc caused a more sustained and extensive decrease in EphA2 levels even at day 3 after treatment, compared to prostate cancer cells treated with 135H12, where EphA2 levels returned after 2 days of treatment ( Figure 2 b). These observations have been made several times with similar agents and a variety of cell lines [ 14 , 15 , 17 , 18 , 21 ], including PC-3 [ 19 , 20 , 24 ], for example reported in Supplementary Figure S1 . While generally we observed that 135H12 has agonistic activity in the low-to sub-micromolar range [ 14 , 15 ], we tested it at 10 μM against PC-3 to assess the ability of the agent to cause a sustained internalization of the receptor over longer periods of time ( Figure 2 ), in view of its anticipated use in vivo.…”

“…Recently, we reported that the dimeric version of 135H11 can efficiently suppress cell migration of pancreatic cancer cells [ 14 , 15 ]. In addition, we also reported previously that earlier generations of agonistic EphA2-targeting-peptide mimetics can be used as carriers for targeted delivery of chemotherapy to breast [ 17 ], pancreatic [ 15 , 18 ], and prostate cancer [ 19 , 20 , 21 ]. In the present study, we aimed at further evaluating the therapeutic potential of targeting EphA2 by agonistic agents 135H12 and ephrinA1-Fc to suppress tumor metastasis in an orthotopic nude-mouse model of prostate cancer.…”

“…Therapeutic targeting of the EphA2-LBD has been pursued in recent years by several different approaches [ 6 , 21 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ] and most studies envisioned the use of agonistic agents as vehicles for targeted delivery of chemotherapy [ 17 , 18 , 19 , 20 , 21 , 24 ]. Indeed, we had recently demonstrated that an earlier generation EphA2-targeting-peptide, when conjugated with paclitaxel, was remarkably effective in inhibiting lung metastases in a syngeneic mouse model of breast cancer [ 17 ]. Such remarkable anti-metastatic activity was attributed to the ability of the drug conjugate to capture and kill circulating tumor cells [ 17 ].…”

Tumor microenvironment complexity and therapeutic implications at a glance

“…Adapted with permission from [154]. Copyright (2017), American Chemical Society paclitaxel is found to be very useful in combating CTCs and preventing the lung metastasis in breast cancer models [168].…”

Therapeutic potential of targeting the Eph/ephrin signaling complex

“…For example, a dimeric form of EphA2-targeting YSA peptide, when conjugated to paclitaxel, is effective in targeting circulating tumor cells and decreasing tumor size in prostate and pancreatic cancer xenograft models and in inhibiting metastases in breast cancer models (Barile et al, 2014; Salem et al, 2018b; Wu et al, 2015b) . Apart from targeting, these peptides can make the conjugated agents more soluble and bioavailable.…”