P11.20 Assessing TTFields-response and associated gene expression in various human cancer cell lines

BACKGROUND

Various cancer cell lines were reported to be affected in an inhibitory manner of varying magnitude by tumor treating fields (TTFields). Here, we aimed to detect response markers for TTFields treatment by analyzing specific properties of cell lines according to their response pattern to these alternating electric fields of intermediate frequency and low intensity.

MATERIAL AND METHODS

We treated 45 cell lines of diverse types of human cancer with TTFields at their specific optimal frequency and equal nominal intensity of 1.7 V/cm for 72 h. In addition to investigating cytotoxicity and clonogenic potential, we used the Cancer Cell Line Encyclopedia (CCLE) database for further analysis: First, to functionally examine patterns of differentially expressed genes or mutations associated with response to TTFields; and second, to compare sensitivity to TTFields using pharmacological profiling (CCLE).

RESULTS

TTFields had a cytotoxic effect on tested cell lines of 50 % on average (range: 14–86% reduced cell counts), whereas the clonogenic effect varied between no effect and 88 % reduction in the number of colonies. With regard to differential gene expression and mutation analysis, our analysis detected upregulated pathways associated with migration, DNA damage repair response, oxidative stress, and hypoxia. Further, cells identified as having a better response to TTFields were also more sensitive to lapatinib, PHA-665752 and PLX-4720.

CONCLUSION

In this study, we determined the optimal frequency for maximum response to TTFields in numerous human cancer cell lines. Our results argue strongly for a vast effectiveness of TTFields treatment in cancer cells, and synergistic effects in combination with other therapeutic agents might be revealed in future studies using pharmacological profiling. Beyond that, further research is needed on the role of identified response-associated mutations.

Acyl-substituted dermaseptin S4 derivatives with improved bactericidal properties, including on oral microflora

The 15-mer dermaseptin S4 derivative S4(1-15) was recently shown to exhibit potent activity against oral pathogens associated with caries and periodontitis. Here, we investigated possible modes for improving the peptide's properties through systematic replacement of an N-terminal amino acid(s) with various fatty acids that modulate the peptide's hydrophobicity and/or charge. Deletion of 1 to 3 residues led to progressive loss of potency as assessed by MIC experiments performed on four test bacteria. Replacing the deleted amino acids with fatty acids most often resulted in potency recovery or improvement, as evidenced by lower MICs and faster bactericidal kinetics in culture media. Best results were obtained after replacement of the N-terminal dipeptide alanine-leucine with heptanoic (C7) or aminododecanoic (NC12) acid. Circular dichroism analysis correlated antibacterial properties to the peptide's secondary structure. MIC experiments and confocal laser scanning microscopy results indicated that C7-S4(3-15) and NC12-S4(3-15) were bactericidal to various oral pathogens, including those which are immobilized in a biofilm. C7-S4(3-15) performed similarly to or better than (depending on growth medium) IB-367, a peptide assessed in clinical trials for treatment of oral mucositis, reducing CFU counts by >3 log units within 2 min of incubation. Collectively, the data indicate that substitution of fatty acids for amino acids may be a useful strategy in revealing improved derivatives of known antimicrobial peptides and suggest the suitability of such compounds for controlling pathogens associated with oral diseases.

In vitro assessment of antimicrobial peptides as potential agents against several oral bacteria

BACKGROUND

Antimicrobial peptides are components of the innate immunity that play an important role in systemic and oral health.

OBJECTIVES

The antibacterial activity of the amphibian-derived K4 -S4(1-15)a antimicrobial peptide was tested against oral pathogens associated with caries and periodontitis and compared with the activities of the human-derived antimicrobial peptides LL-37 and dhvar4a.

METHODS

Growth inhibition of planktonic bacteria was tested using standard microdilution assays. Live/Dead staining followed by confocal scanning laser microscopy (CSLM) was used to determine the bactericidal effect of K4 -S4(1-15)a on Streptococcus mutans attached to a glass surface or grown as biofilm.

RESULTS

The cariogenic species S. mutans, Streptococcus sobrinus, Lactobacillus paracasei and Actinomyces viscosus were resistant to LL-37 found in the oral cavity. Porphyromonas gingivalis was the species most resistant to the three tested peptides. K4 -S4(1-15)a demonstrated the highest activity against the tested planktonic bacteria. In addition, K4 -S4(1-15)a was bactericidal to surface-attached S. mutans as well as to S. mutans biofilms grown in vitro. However, surface attachment increased S. mutans resistance to the antimicrobial peptide.

CONCLUSIONS

Our results support growing evidence suggesting the use of antimicrobial peptides for prevention and treatment of oral disease.

Enhanced-resolution image restoration from a sequence of low-frequency vibrated images by use of convex projections

An algorithm to increase the spatial resolution of digital video sequences captured with a camera that is subject to mechanical vibration is developed. The blur caused by vibration of the camera is often the primary cause for image degradation. We address the degradation caused by low-frequency vibrations (vibrations for which the exposure time is less than the vibration period). The blur caused by low-frequency vibrations differs from other types by having a random shape and displacement. The different displacement of each frame makes the approach used in superresolution (SR) algorithms suitable for resolution enhancement. However, SR algorithms that were developed for general types of blur should be adapted to the specific characteristics of low-frequency vibration blur. We use the method of projection onto convex sets together with a motion estimation method specially adapted to low-frequency vibration blur characteristics. We also show that the random blur characterizing low-frequency vibration requires selection of the frames prior to processing. The restoration performance as well as the frame selection criteria is dependent mainly on the motion estimation precision.