Canertinib induces ototoxicity in three preclinical models

Nrg1/ErbB2 regulates differentiation and apoptosis of neural stem cells in the cochlear nucleus through PI3K/Akt pathway

Sensorineural hearing loss (SNHL) is a common causes of disability. Neural stem cells (NSCs) from the cochlear nuclei have been considered to be a potential direction for the treatment of SNHL. Neuregulin 1 (NRG1)/ErbB2 signaling displays an essential role in nervous system development. In this study, we aimed to explore the roles of NRG1/ErbB2 in differentiation and apoptosis of cochlear nuclei NSCs. The data showed that the expression of NGR1 and ErbB2 in cochlear nuclei NSCs isolated from rats were increased with the age of rats. NRG1 treatment reduced the nestin-positive cells number, increased the MAP2-positive and GFAP-positive cells number, decreased the expression of cleaved-caspase-3, and increased the activation of PI3K/AKT. ErbB2 knockdown by lentiviral-mediated ErbB2 shRNA infection reversed the effect of NRG1 on cochlear nuclei NSCs. LY294002 administration further enhanced the effect of ErbB2 silencing on the expression of nestin, MAP2, GFAP and cleaved-caspase-3. Taken together, NRG1/ErbB2 regulates differentiation and apoptosis of cochlear nucleus NSCs through PI3K/Akt pathway.

NRG/ErbB signaling regulates neonatal muscle growth but not neuromuscular contractures in neonatal brachial plexus injury

Neonatal brachial plexus injury (NBPI) causes disabling and incurable muscle contractures that are driven by impaired growth of denervated muscles. A rare form of NBPI, which maintains afferent muscle innervation despite motor denervation, does not cause contractures. As afferent innervation regulates various aspects of skeletal muscle homeostasis through NRG/ErbB signaling, our current study investigated the role of this pathway in modulating contracture development. Through pharmacologic modification with an ErbB antagonist and NRG1 isoforms, we discovered that NRG/ErbB signaling does not modulate the development of contractures in neonatal mice. Instead, ErbB inhibition impeded growth in nondenervated skeletal muscles, whereas increased ErbB activation exacerbated denervation-induced skeletal muscle atrophy. This potential regulatory effect of NRG/ErbB signaling on neonatal muscle growth warrants deeper investigation.

Early Physiological and Cellular Indicators of Cisplatin-Induced Ototoxicity

Cisplatin chemotherapy often causes permanent hearing loss, which leads to a multifaceted decrease in quality of life. Identification of early cisplatin-induced cochlear damage would greatly improve clinical diagnosis and provide potential drug targets to prevent cisplatin's ototoxicity. With improved functional and immunocytochemical assays, a recent seminal discovery revealed that synaptic loss between inner hair cells and spiral ganglion neurons is a major form of early cochlear damage induced by noise exposure or aging. This breakthrough discovery prompted the current study to determine early functional, cellular, and molecular changes for cisplatin-induced hearing loss, in part to determine if synapse injury is caused by cisplatin exposure. Cisplatin was delivered in one to three treatment cycles to both male and female mice. After the cisplatin treatment of three cycles, threshold shift was observed across frequencies tested like previous studies. After the treatment of two cycles, beside loss of outer hair cells and an increase in high-frequency hearing thresholds, a significant latency delay of auditory brainstem response wave 1 was observed, including at a frequency region where there were no changes in hearing thresholds. The wave 1 latency delay was detected as early cisplatin-induced ototoxicity after only one cycle of treatment, in which no significant threshold shift was found. In the same mice, mitochondrial loss in the base of the cochlea and declining mitochondrial morphometric health were observed. Thus, we have identified early spiral ganglion-associated functional and cellular changes after cisplatin treatment that precede significant threshold shift.

Safety and Tolerability of Epidermal Growth Factor Receptor (EGFR) Tyrosine Kinase Inhibitors in Oncology

Tyrosine kinase inhibitors (TKIs) that target epidermal growth factor receptor (EGFR) have dramatically improved progression-free survival in non-small-cell lung cancer (NSCLC) patients who carry sensitizing EGFR-activating mutations and in patients with breast and pancreatic cancers. However, EGFR-TKIs are associated with significant and disabling undesirable effects that adversely impact on quality of life and compliance. These effects include dermatological reactions, diarrhoea, hepatotoxicity, stomatitis, interstitial lung disease and ocular toxicity. Each individual EGFR-TKI is also associated with additional adverse effect(s) that are not shared widely by the other members of its class. Often, these effects call for dose reduction, treatment discontinuation or pharmacotherapeutic intervention. Since dermatological effects result from on-target effects on wild-type EGFR, rash is often considered to be a biomarker of efficacy. A number of studies have reported better outcomes in patients with skin reactions compared with those without. This has led to a 'dosing-to-rash' strategy to optimize therapeutic outcomes. Although conceptually attractive, there is currently insufficient evidence-based support for this strategy. While skin reactions following EGFR-TKIs are believed to result from an effect on wild-type EGFR, their efficacy is related to effects on mutant variants of EGFR. It is noteworthy that newer EGFR-TKIs that spare wild-type EGFR are associated with fewer dermatological reactions. Furthermore, secondary mutations such as T790M in exon 20 often lead to development of resistance to the clinical activity and efficacy of first- and second-generation EGFR-TKIs. This has stimulated the search for later-generations of EGFR-TKIs with the ability to overcome this resistance and with greater target selectivity to spare wild-type EGFR in expectations of an improved safety profile. However, available data reviewed herein indicate that not only are these newer agents associated with the aforementioned adverse effects typical of earlier agents, but they are also susceptible to resistance due to tertiary mutations, most frequently C797S. At least three later-generation EGFR-TKIs, canertinib, naquotinib and rociletinib, have been discontinued from further development in NSCLC following concerns about their safety and risk/benefit.

Ascitic fluid from advanced ovarian cancer patients compromises the activity of receptor tyrosine kinase inhibitors in 3D cell clusters of ovarian cancer cells

Ovarian cancer patients in the advanced stages of the disease show clinical ascites, which is associated with a poor prognosis. There is limited understanding of the effect of ascitic fluid on ovarian cancer cells and their response to anticancer drugs. We investigated the antitumour effects of EGFR/Her-2 (canertinib) and c-Met (PHA665752) inhibitors in a 3D cell model of three ovarian cancer lines. Single and combined inhibitor treatments affected cell growth of OVCAR-5 and SKOV-3 cell lines but not OV-90 cell line. Growth reduction was correlated with the down expression of PCNA, EGFR, HER-2, c-MET, ERK and AKT and their phosphorylation status in cells in growth factor supplemented media. However, these effects were not re-producible in OVCAR-5 and SKOV-3 cell lines when they were exposed to ascitic fluid obtained from three ovarian cancer patients. Serum albumin and protein components in the ascitic fluids may reduce the cellular uptake of the inhibitors.

Tumor cell resistance against targeted therapeutics: the density of cultured glioma tumor cells enhances Stat3 activity and offers protection against the tyrosine kinase inhibitor canertinib

Tumor cell resistance to drug treatment severely limits the therapeutic success of treatment.

Tumor cell resistance to drug treatment severely limits the therapeutic success of treatment. Tumor cells, exposed to chemotherapeutic drugs, have developed intricate strategies to escape the cytotoxic effects and adapt to adverse conditions. The molecular mechanisms causing drug resistance can be based upon modifications of drug transport or metabolism, structural alterations of drug targets or adaptation of cellular signaling. An important component in the transformation of cells and the emergence of drug resistance is the activation of the transcription factor Stat3. The persistent, inappropriate activation of Stat3 causes the expression of target genes which promote tumor cell proliferation, survival, invasion and immune suppression, and it is instrumental in the process of the emergence of resistance to both conventional chemotherapeutic agents and novel targeted compounds. For these reasons, Stat3 inhibition is being pursued as a promising therapeutic strategy. We have investigated the effects of the tyrosine kinase inhibitor canertinib on the glioma cell line Tu-2449. In these cells Stat3 is persistently phosphorylated and activated downstream of the oncogenic driver v-Src and its effector, the cytoplasmic tyrosine kinase Bmx. Canertinib exposure of Tu-2449 cells rapidly caused the inhibition of the Bmx kinase and the deactivation of Stat3. Prolonged exposure of the cells to canertinib caused the death of the large majority of the cells. Only a few cells became resistant to canertinib and survived in tight clusters. These cells have become drug resistant. When the canertinib resistant cells were expanded and cultured at lower cell densities, they regained their sensitivity towards canertinib. We measured the extent of Stat3 activation as a function of cell density and found that higher cell densities are accompanied by increased Stat3 activation and a higher expression of Stat3 target genes. We suggest that Stat3 induction through tight cell–cell interactions, most likely through the engagement of cadherins, can counteract the inhibitory effects exerted by canertinib on Bmx. Cell–cell interactions induced Stat3 and compensated for the suppression of Stat3 by canertinib, thus transiently protecting the cells from the cytotoxic effects of the inhibitor.