Cetuximab and panitumumab, monoclonal antibodies direct against the epidermal growth factor receptor (EGFR) are a therapeutic option for mCRC patients wild type for KRAS and NRAS genes. However, only a subset of mCRC patients receives clinical benefit from these therapies due to the development of resistance mechanisms. HER2 gene amplification or HER2 activating mutations have been implicated as resistance mechanisms to anti-EGFR therapies. However, little is known about the role of HER2 in cancer resistance to anti-EGFR antibodies.
We transfected colon cancer cells sensitive to anti-EGFR antibodies (LIM1215 and SW48) with HER2 vector in order to obtain stable clones overexpressing HER2 protein. LIM1215-HER2 and SW48-HER2 cells were characterized by their morphological and molecular profile through cell migration and WB assays. Moreover, different drugs sensitivity was evaluated by MTT and colony formation. Furthermore, HER2 amplified cells were engrafted into nude mice and treated with different drugs.
HER2 amplified cells show an overexpression and activation of the HER family receptors coupled by an intracellular downstream activation pathway of AKT, MAPK, and MEK proteins compared to parental cells. HER2 amplified cells were treated with several combinations of drugs directed against HER receptors, such as anti-EGFR antibodies of first, second and third generation (cetuximab, SYM004 and MM151); trastuzumab, pertuzumab and lapatinib directed against HER2 receptor; and duligotuzumab direct against HER3. Subsequently, both cells were treated with drugs directed against MEK and PI3KCA proteins, such as refametinib and pictilisib. Among these therapeutic options, the combination of refametinib and pictilisib have shown the most synergist anti-proliferative activity. The in vivo xenograft CRC models have confirmed the synergistic antitumor activity of this combined treatment. Moreover, PDTX HER amplified CRC models will be used to validate the previous results.
These results suggest that the treatment with refamentinib and pictilisib could be a strategy for patients with HER2 amplification that do not receive clinical benefit from standard anti-EGFR therapies.
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Legal entity responsible for the study
Università Degli Studi della Campania Luigi Vanvitelli.
Has not received any funding.
All authors have declared no conflicts of interest.