HER2-Targeted Tyrosine Kinase Inhibitors Cause Therapy-Induced-Senescence in Breast Cancer Cells

Abstract

Prolonged treatment of HER2 positive breast cancer cells with tyrosine kinase inhibitors (TKIs) leads to the emergence of acquired resistance. However, the effects of continuous TKI exposure on cell fate, and the steps leading to the acquisition of a resistant phenotype are poorly understood. To explore this, we exposed five HER2 positive cells lines to HER2 targeted therapies for periods of up to 4 weeks and examined senescence associated β-galactosidase (SA-β-gal) activity together with additional markers of senescence. We found that lapatinib treatment resulted in phenotypic alterations consistent with a senescent phenotype and strong SA-β-gal activity in HER2-positive cell lines. Lapatinib-induced senescence was associated with elevated levels of p15 and p27 but was not dependent on the expression of p16 or p21. Restoring wild type p53 activity either by transfection or by treatment with APR-246, a molecule which reactivates mutant p53, blocked lapatinib-induced senescence and caused increased cell death. In contrast to lapatinib, SA-β-gal activity was not induced by exposing the cells to trastuzumab as a single agent but co-administration of lapatinib and trastuzumab induced senescence, as did treatment of the cells with the irreversible HER2 TKIs neratinib and afatinib. Neratinib- and afatinib-induced senescence was not reversed by removing the drug whereas lapatinib-induced senescence was reversible. In summary, therapy-induced senescence represents a novel mechanism of action of HER2 targeting agents and may be a potential pathway for the emergence of resistance.

Therapy-Induced Senescence: An “Old” Friend Becomes the Enemy

“…Inhibition of protein kinase signaling downstream of the HER2 receptor has proven effective in the treatment of HER2-positive breast cancer. A recent report revealed that several of these kinase inhibitors such as lapatinib, neratinib and afatinib induced senescence in HER2-positive breast cancer cells lines marked by robust SA-β-gal induction and growth inhibition [109]. Interestingly, in the tested models, direct HER2 inhibition by trastuzumab monotherapy failed to induce senescence [109].…”

“…A recent report revealed that several of these kinase inhibitors such as lapatinib, neratinib and afatinib induced senescence in HER2-positive breast cancer cells lines marked by robust SA-β-gal induction and growth inhibition [109]. Interestingly, in the tested models, direct HER2 inhibition by trastuzumab monotherapy failed to induce senescence [109]. Conversely, EGFR inhibitors such as gefitinib and erlotinib have been reported to induce senescence in EGFR-mutant and non-mutant NSCLC cell lines [110,111].…”

“…For example, both rituximab and obinutuzumab (anti-CD20 monoclonal antibodies) can effectively induce senescence (as well as apoptosis) in follicular lymphoma models [49]. Pertuzumab and trastuzumab, monoclonal antibodies used for the treatment of HER-2-positive breast cancer, were shown to promote senescence in breast cancer models [115]; however, in another report, trastuzumab alone failed to induce robust senescence [109].…”

Intratumor Heterogeneity and Therapy Resistance: Contributions of Dormancy, Apoptosis Reversal (Anastasis) and Cell Fusion to Disease Recurrence

“…Cancer cells lacking wild-type p53 activity can also undergo SIPS through p21-dependent [79,80] and independent mechanisms [81]. In addition to p21, CDK inhibitors that can drive SIPS include p16 INK4a , p15 INK4b , and p27 KIP1 [80][81][82].…”

“…The beneficial and harmful consequences of this so-called "senescence-associated secretory phenotype" (SASP) has been the subject of much discussion (e.g., [73,83,84]). In addition to detrimental effects of SASP in the context of cancer therapy, the proliferation-arrested state in solid tumor cells that have undergone SIPS is often reversible, leading to disease relapse [82,85,86]. Furthermore, under some conditions, depending on cell type and level/type of genotoxic stress, solid tumor cells undergoing SIPS can become multinucleated and/or polyploid, entering the PGCC-stemness-tumor repopulation cycle [41,[85][86][87][88].…”