Synergistic Blockade of EGFR and HER2 by New-Generation EGFR Tyrosine Kinase Inhibitor Enhances Radiation Effect in Bladder Cancer Cells

Abstract

Blockade of EGFR has been proved useful in enhancing the effect of radiotherapy, but the advantages of new-generation EGFR tyrosine kinase inhibitors (TKI) in radiosensitization are not well known. We used two human bladder cancer cells with wild-type EGFR to study the synergism between irradiation and afatinib (an EGFR/HER2 dual kinase inhibitor) or erlotinib (an EGFR kinase inhibitor). Here, we showed that afatinib has better radiosensitizing effect than erlotinib in increasing cancer cell killing, the percentage of apoptotic cells, and DNA damage. Afatinib is also superior to erlotinib in combining radiation to decrease tumor size, inhibit glucose metabolism, and enhance apoptotic proteins in vivo. Finally, erlotinib suppressed cell growth and induced more DNA damage in bladder cancer cells transfected with HER2 shRNA, but not in control vector-treated cells. In conclusion, concomitant blockade of radiation-activated EGFR and HER2 signaling by a new-generation EGFR TKI better inhibits the growth of bladder cancer cells both in vitro and in vivo. The absence of radiosensitization by EGFR inhibition alone and the greater radiosensitizing effect of EGFR inhibitor in HER2 knocked down cells suggest the synergism between HER2 and EGFR in determining radiosensitivity. The regained radiosensitizing activity of erlotinib implies that with proper HER2 inhibition, EGFR tyrosine kinase is still a potential target to enhance radiotherapy effect in these seemingly unresponsive bladder cancer cells.

Overexpression of Epidermal Growth Factor Receptor (EGFR) and HER-2 in Bladder Carcinoma and Its Association with Patients’ Clinical Features

“…The epidermal growth factor receptor (EGFR) family has been implicated in tumor cell growth and differentiation, including EGFR, HER-2, HER-3, and HER-4 [ 6 ]. Many solid tumors have been found to overexpress EGFR, such as head and neck [ 7 ], lung [ 8 ], colon [ 9 ], breast [ 10 ], kidney [ 11 ], prostate, and bladder cancer [ 12 ].…”

“…HER-2 overexpression had studied extensively in breast carcinoma [ 14 ], and HER-2 is over-expressed in approximately 20% of primary invasive breast carcinomas [ 15 ] and is associated with poor prognosis [ 16 ]. Previous experiments have reported that EGFR and HER-2 are expressed in bladder cancer [ 17 ]. In the present study, we used immunohistochemistry to determine the expression of EGFR/HER-2, and to investigate their association with patients’ clinical features, pathological grade, and tumor recurrence, in hope of finding a new therapeutic strategy for bladder carcinoma.…”

Concurrent EGFR-TKI and Thoracic Radiotherapy as First-Line Treatment for Stage IV Non-Small Cell Lung Cancer Harboring EGFR Active Mutations

“…Most patients receiving first‐generation EGFR‐tyrosine kinase inhibitor (TKI) undergo disease progression after 8.4 to 13.1 months of treatment, and the majority have local progression . It has been reported that EGFR‐TKI could increase radiosensitivity and that radiotherapy could reduce EGFR‐TKI resistance . Moreover, several studies showed effective local control by EGFR‐TKI combined with radiotherapy in metastatic sites of advanced non‐small cell lung cancer (NSCLC) harboring EGFR active mutations .…”

Perspectives For Target Therapy In The Treatment Of Malignant Neoplasms Of The Urinary Bladder

“…Но едновременното блокиране на активираните от радиацията EGFR и HER2 сигнални пътища с тирозин-киназни инхибитори от ново поколение по-добре се отразява на потискането на растежа на раковите клетки на пикочния мехур както in vitro, така и in vivo. Това предполага, че приложението на ерлотиниб заедно с подходящ HER2-инхибитор ще доведе до по-добър терапевтичен ефект при лъчелечение на "привидно" нечувствителните ракови клетки на пикочния мехур (28).…”