Critical-size Defect Augmentation Using Sintered and Non-Sintered Bovine Bone Matrix - An Experimental Controlled Study in Minipigs.

PURPOSE: Xenogeneic bone substitute materials are often used for augmentation of larger bone defects. Purification methods for these materials vary, mainly in terms of temperature. The aim of this study was to determine in vivo how sintering affects quantitative and qualitative bone regeneration of 2 bovine augmentation materials. METHODS: A total of 56 critical size defects were set at the frontal bone of 14 domestic pigs (4 each) and filled randomly with either bovine, sintered hydroxyapatite (BO), bovine, non-sintered hydroxyapatite (BOS), local autologous bone (AB) or left empty. All defects were additionally covered with a collagen membrane. Specimens were harvested after 4 and 8 weeks and were evaluated histologically and histomorphometrically. RESULTS: Histologically new bone could be seen in every group. Significantly highest new bone formation was found in AB. No significant difference could be detected between BO and BOS. CONCLUSIONS: According to the results of this study, sintered bone substitute material remains histologically distinguishable but does not affect quantitative and qualitative bone regeneration.

Multi-kinase inhibitors and cisplatin for head and neck cancer treatment in vitro.

Multidrug resistance (MDR) remains one of the major causes of suboptimal outcome following therapy in head and neck squamous cell carcinoma (HNSCC). ATP-binding cassette (ABC) transporters are overexpressed in HNSCC, which contributes to the limited effect of chemotherapeutic treatment. In addition to their named function, tyrosine kinase inhibitors (TKIs) have been revealed to impact on ABC transporter activity and expression. Therefore, the present study aimed to investigate the effects of combination therapy using different TKIs combined with cisplatin. Reverse transcription-quantitative PCR was used to characterize ABC transporter and receptor expression in 5 HNSCC cell lines treated with 3 different TKIs (pazopanib, dovitinib, nintedanib) and cisplatin. Treatment efficacy was analyzed using a crystal violet staining assay. Analysis of ABC transporter (ABCB1, ABCC1 and ABCG2) genetic alterations was performed using The Cancer Genome Atlas. Statistical analysis was conducted to evaluate the effects of mono- and combination treatment. With the exception of ABCB1, all of the investigated ABC transporters were expressed in each cell line. The additive effects of TKI + cisplatin combination treatment were observed for pazopanib in three cell lines, nintedanib in four cell lines, and were not observed for dovitinib in any of the cell lines investigated. The combination of multi-kinase inhibitors and conventional chemotherapy in HNSCC may strengthen the use of current therapeutic strategies; nintedanib appears to be the most suitable TKI for combination therapy. Further efforts are required to classify TKI efficacy with regard to cisplatin resistance.

Targeting VEGFR and FGFR in head and neck squamous cell carcinoma in vitro.

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous disease characterized by a tumor microenvironment (TME) that overexpresses vascular endothelial growth factor receptor (VEGFR) and fibroblast growth factor receptor (FGFR), which can lead to neovascularization, tumor growth and metastasis. Therapeutic strategies inhibiting these signaling pathways might lead to innovative HNSCC treatments. Five HNSCC cell lines were characterized based on VEGFR1-3 and FGFR1-4 expression by sqRT-PCR and treated with three different tyrosine kinase inhibitors (TKIs) (nintedanib, dovitinib and pazopanib), all of which are effective against VEGFR and FGFR family members. Crystal violet assays were performed to analyze the effect of the treatments on cell growth (viability). Additionally, VEGFR1-3 and FGFR1-4 expression data were retrieved from The Cancer Genome Atlas (TCGA), and statistical analyses were performed to investigate the receptor expression level in the different cell lines and the efficacy of the single-agent treatments. A correlation analysis was performed to quantify the degree of relationship between receptor expression and drug efficacy. With the exception of VEGFR2, the targeted receptors were expressed at different levels in all of the cell lines. The cell lines exhibited concentration-dependent responses with cell line-specific differences toward two of the three TKIs (nintedanib and dovitinib). Notably, all of the cell lines were resistant to pazopanib. TKIs have potential as therapeutic agents for HNSCC. Cell line-specific differences were observed in our in vitro experiments. The observed pazopanib resistance could be explained by receptor expression. Further investigation is required to determine TKI efficacy in HNSCC.

Co-treatment of wild-type EGFR head and neck cancer cell lines with afatinib and cisplatin.

Treatment of head and neck squamous cell carcinoma (HNSCC) remains challenging. Non­surgical approaches typically comprise radiotherapy and antineoplastic chemotherapy, of which platinum­based agents are the most common. Similar to other malignancies, targeted therapies have an increasing role in the treatment of head and neck cancer. The overexpression of epidermal growth factor receptor (EGFR) is a useful target for specific therapeutic strategies. Resistance to EGFR­directed therapies, including cetuximab, is partly mediated by the activation of alternative receptors and pathways. Therefore, other members of the ErbB family, including human epidermal growth factor receptor (HER)2 and HER4, may have important therapeutic roles. The aim of the present study was to investigate the efficacy of afatinib, an EGFR/HER2/HER4 tyrosine kinase inhibitor, in combination with cisplatin in HNSCC cell lines. The cisplatin concentration used was set at cell line­specific half maximal inhibitory concentration values. Since the vast majority of head and neck cancers do not exhibit any EGFR tyrosine kinase domain mutations, five human EGFR wild­type HNSCC cell lines were used in the present study. For statistical analyses, non­parametric Mann­Whitney tests were conducted. The present study detected a concentration­dependent efficacy of afatinib. In three out of the five cell lines (PCI­9, PCI­52 and PCI­68), 0.625 µM afatinib in combination with cisplatin exerted significant antiproliferative effects. In the two other cell lines (PCI­1 and PCI­13), significant effects were observed following treatment with ≥1.25 µM afatinib. Notably, compared with the findings of previous studies, cell lines (PCI-9 and PCI-52) less vulnerable to erlotinib or gefitinib were more vulnerable to the afatinib/cisplatin combination, and vice versa. Differences in the treatment success of erlotinib/gefitinib (targeting only EGFR) and afatinib (targeting EGFR, HER2 and HER4) may be explained by mutations in the EGFR. Therefore, afatinib treatment may be considered an important therapeutic option for patients failing cetuximab treatment. In addition, the present study demonstrated significant enhancement of platinum­based therapies upon the addition of various afatinib concentrations. These results provide preclinical evidence to advocate further in vivo studies and clinical trials.