Mechanism of action of the trastuzumab biosimilar CT-P6.

Objectives: Therapeutic monoclonal antibody biosimilars are expected to help reduce the sizeable economic burden of targeted treatments. Trastuzumab (Herceptin®), a recombinant humanized monoclonal antibody that binds to the extracellular domain of HER2, is approved for use in HER2-overexpressing breast cancer (in both the adjuvant and metastatic settings) and HER2-positive gastric cancer. CT-P6 (Herzuma®) is a biosimilar of trastuzumab, designed to bind with high affinity and specificity to the same HER2 epitope as the reference product. We investigated whether CT-P6 exerts its effects through the same mechanism of action as trastuzumab. Methods: The mechanism of action of CT-P6 and trastuzumab, both as monotherapy and in combination with paclitaxel or pertuzumab, was compared in HER2-overexpressing breast cancer and gastric cancer cell models. Results: We confirmed that CT-P6 functions in a manner similar to trastuzumab by binding to the HER2 receptor, which is central to the effects of trastuzumab in all indications. Conclusions: Collectively, the results of this study show that the mechanisms of action of CT-P6 and trastuzumab are similar in HER2-positive breast cancer and gastric cancer models and, therefore, CT-P6 can be expected to perform similarly in the clinical setting.

Effect of epidermal growth factor receptor inhibitor alone and in combination with cisplatin on growth of vulvar cancer cells.

A recent study reported on the efficacy of the EGFR inhibitor on locally advanced vulvar cancer. The aim of this study was to evaluate the effect of an EGFR tyrosine kinase inhibitor (AG1478) alone and in combination with cisplatin on vulvar cancer cells (A431 and SW962). We detected overexpression of EGFR in A431 cells and low expression in SW962 cells. We found that the growth inhibitory effect of AG1478 was dependent upon the expression level of EGFR. The combined treatment of AG1478 with cisplatin failed to exert any synergistic or additive effect in either cell line. In the EGFR signaling pathway, AG1478 decreased the phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) in parallel with decreased activity of EGFR in A431 cells, while no changes in ERK and Akt were observed in SW962 cells. The combination of AG1478 with cisplatin completely inhibited the phosphorylation of ERK and Akt in A431 cells but not in SW962 cells. Cisplatin alone and its combination with AG1478 increased the phosphorylation of p38 and c-Jun N-terminal kinase (JNK) in both cell lines. In summary, AG1478 inhibited the growth activity of vulvar cancer cells, depending upon the expression level of EGFR, by inhibiting the activities of EGFR, Akt, and ERK. Given the absence of synergistic effects from the combination of AG1478 with cisplatin, combination therapy should be considered cautiously.

Influences of cyclooxygenase-1 and -2 expression on the radiosensitivities of human cervical cancer cell lines.

We utilized three cervical cancer cell lines (HeLa, HT-3, and C33A) and clonogenic assays to determine whether cyclooxygenase (COX) expression is related to radiosensitivity. Using COX DNA transfection and COX inhibition by siRNA, we also examined changes in radiosensitivity caused by variations in COX expression. The survival fractions of HeLa and HT-3 cell lines, which both with COX-1 and COX-2 activity, were found to be significantly higher than that of the C33A cell line which had neither COX-1 nor COX-2 activity. Moreover, the acquisition of COX-1 in C33A cell line significantly reduced its radiosensitivity, but COX-2 transfection increased radiosensitivity in this cell line. In addition, the inhibition of COX-1 activity in HT-3 cell line using siRNA resulted in an increased radiosensitivity, but this phenomenon was not observed for COX-2 inhibition. The same experiment in HeLa cells using siRNA also showed no significant change in radiosensitivity. The results obtained during this study suggest that COX expression is associated with the radiosensitivity in uterine cervical cancer cell lines and COX-1 might have more important role than COX-2.

Apoptotic effect of celecoxib dependent upon p53 status in human ovarian cancer cells.

Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, induces the apoptosis in various cancers in COX-2 dependent and/or independent manners. The p53 protein is mutated in 50% of all human tumors and plays a key role in apoptosis, cell cycle, and the expression of several proteins. In ovarian cancer, the rate of p53 mutation has been shown to be very high and associated with poor prognosis. To explore the importance of functional status of p53 in apoptosis by celecoxib in ovarian cancer cells, the cellular response to celecoxib was determined in SK-OV3 ovarian cancer cells with null type p53 and PA-1 with wild-type p53. Our results showed that celecoxib inhibited cell growth more in PA-1 than in SK-OV3. The underlying antiproliferative mechanism may differ between these two cell types dependent upon the functional status of p53, which plays integral roles in regulating cell cycle and survival. Higher sub-G1 was shown in PA-1 than in SK-OV3 in response to celecoxib (PA-1 versus SK-OV3; 60.28% versus 6.69%). Caspase -8, -9, and -3 were activated in PA-1 cells, but not in SK-OV3 cells. These results suggest that death receptor and mitochondria-mediated apoptotic pathways may be involved in celecoxib-induced apoptosis dependent upon the functional status of p53. Our article demonstrated that the celecoxib effectively inhibited cell growth and induced apoptosis in human ovarian cancer cells with wild-type p53. Thus, apoptotic effect by celecoxib seemed to be different dependent upon the functional status of p53.