Trastuzumab-DM1 causes tumour growth inhibition by mitotic catastrophe in trastuzumab-resistant breast cancer cells in vivo

Abstract

IntroductionTrastuzumab is widely used for the treatment of HER2-positive breast cancer. Despite encouraging clinical results, a significant fraction of patients are, or become, refractory to the drug. To overcome this, trastuzumab-DM1 (T-DM1), a newer, more potent drug has been introduced. We tested the efficacy and mechanisms of action of T-DM1 in nine HER2-positive breast cancer cell lines in vitro and in vivo. The nine cell lines studied included UACC-893, MDA-453 and JIMT-1, which are resistant to both trastuzumab and lapatinib.MethodsAlamarBlue cell-proliferation assay was used to determine the growth response of breast cancer cell lines to trastuzumab and T-DM1 in vitro. Trastuzumab- and T-DM1-mediated antibody-dependent cellular cytotoxicity (ADCC) was analysed by measuring the lactate dehydrogenase released from the cancer cells as a result of ADCC activity of peripheral blood mononuclear cells. Severe Combined Immunodeficient (SCID) mice were inoculated with trastuzumab-resistant JIMT-1 cells to investigate the tumour inhibitory effect of T-DM1 in vivo. The xenograft samples were investigated using histology and immunohistochemistry.ResultsT-DM1 was strongly growth inhibitory on all investigated HER2-positive breast cancer cell lines in vitro. T-DM1 also evoked antibody-dependent cellular cytotoxicity (ADCC) similar to that of trastuzumab. Outgrowth of JIMT-1 xenograft tumours in SCID mice was significantly inhibited by T-DM1. Histologically, the cellular response to T-DM1 consisted of apoptosis and mitotic catastrophe, the latter evidenced by an increased number of cells with aberrant mitotic figures and giant multinucleated cells.ConclusionsOur results suggest mitotic catastrophe as a previously undescribed mechanism of action of T-DM1. T-DM1 was found effective even on breast cancer cell lines with moderate HER2 expression levels and cross-resistance to trastuzumab and lapatinib (MDA-453 and JIMT-1).

Preclinical studies of a Pro-antibody-drug conjugate designed to selectively target EGFR-overexpressing tumors with improved therapeutic efficacy

“…Treatment with activated PanP-DM1 resulted in the remarkable G2/M phase arrest, which may directly lead to cell apoptosis ( Fig 4B and C). 27,35 The percentage of cells in the G2/M phase increased from 19.69 § 1.809% to 30.92 § 1.097% in activated PanP-DM1-treated culture and from 19.69 § 1.809% to 25.92 § 1.092 % in PanP-DM1-treated culture (Fig 4C). These results revealed that non-activated PanP-DM1 was less effective than activated PanP-DM1 in inducing G2/M arrest on A431 cells (P<0.05), which is likely attributable to reduced antigen-binding ability.…”

“…45 ADC has become a powerful treatment strategy to overcome drug resistance like trastuzumab resistance. 35 The efficacy of PanP-DM1 on the cancer cells that are refractory to EGFR-directed antibodies will be explored in a future research publication.…”

The Preclinical Profile of the Duocarmycin-Based HER2-Targeting ADC SYD985 Predicts for Clinical Benefit in Low HER2-Expressing Breast Cancers

“…S4B; refs. 16,17). Importantly, SYD985 retained its activity in cell lines with lower HER2 expression, whereas T-DM1 became less potent with IC 50 values of 32.4 and 112.1 ng/mL in SK-OV-3, 67.4 and 313.9 ng/mL in MDA-MB-175-VII, and 14.9 and >1,000 ng/mL in ZR-75-1, for SYD985 and T-DM1, respectively (see Supplementary Table S2 for the percentage efficacy and 95% confidence intervals).…”

La montée en puissance des immunoconjugués en oncologie

“…Des études précliniques suggèrent qu'il conserve les mécanismes d'action d'Herceptin ® , l'induction de l'apoptose par inhibition de la voie de signalisation PI3K (phosphoinositide 3-kinase)/AKT (protéine kinase B), l'inhibition du shedding de HER2 et l'induction de la cytotoxicité cellulaire dépendante des anticorps (ADCC) [16]. De plus, il présente une activité antitumorale dans les modèles expérimentaux résistant à l'Herceptin ® et au Tyverb ® [16,17]. L'homologation de Kadcyla ® s'appuie sur les résultats de l'étude de phase III EMILIA, qui a comparé Kadcyla ® utilisé seul au traitement de référence associant Tyverb ® et Xeloda ® , chez 991 patientes souffrant de cancer du sein HER2-positif avancé ou métastatique et ayant été précédemment traitées par l'Herceptin ® et un taxane [18].…”