Models of head and neck squamous cell carcinoma using bioengineering approaches.

The use of bioengineering methods and approaches is extremely promising for the development of experimental models of cancer, especially head and neck squamous cell carcinomas (HNSCC) that are characterized by early metastasis and rapid progression., for testing novel anticancer drugs and diagnostics. This review summarizes the most relevant HNSCC tumor models used to this day as well as future directions for improved modeling of the malignant disease. Apart from conventional 2D-cell cultivation methods and in vivo animal cancer models a number of bioengineering techniques of modeling HNSCC tumors were reported: genetic-engineering, ethanol/tobacco exposure experiment, spheroids, hydrogel-based cell culture, scaffold-based cell culture, microfluidics, bone-tumor niche cell culture, cancer and normal cells co-culture, cancer cells, and bacteria co-culture. An organized set of these models can constitute a system of HNSCC experimental modeling, which gives potential towards developing the newest approaches in the diagnosis, prevention, and treatment of HNSCC.

Reduced susceptibility and resistance to bedaquiline in clinical M. tuberculosis isolates.

OBJECTIVES: Bedaquiline is an effective drug used to treat MDR and XDR tuberculosis, providing high cure rates in complex therapy. Mutations in the mmpR (rv0678) and atpE genes are associated with reduced susceptibility to bedaquiline and have been identified in both in vitro selected strains and clinical isolates. However, the phenotypic criteria used to detect bedaquiline resistance have yet to be established due to the collection of few clinical isolates from patients receiving bedaquiline-containing treatment regimens. METHODS: One hundred eighty-two clinical isolates from 74 patients receiving bedaquiline and 163 isolates from 107 patients not exposed to bedaquiline were analysed. The bedaquiline MICs were tested using serial dilutions on 7H11 agar plates and the Bactec MGIT 960 system. The mmpR and atpE genes were sequenced by Sanger sequencing. RESULTS: The 7H11 agar method allowed for rapid discrimination between mutated and wild-type isolates and between exposed and non-exposed isolates. Seventy-three percent of bedaquiline-exposed isolates, as well as 91% of isolates with mutations, had an elevated bedaquiline MIC (≥ 0.12 mg/L on 7H11 media) compared to the reference isolates (89% had an MIC ≤ 0.03 mg/L). Previously reported in vitro-selected mutants (E61D and A63P) and novel AtpE substitutions (G25S and D28G) were observed in the clinical isolates. Substitutions in codon 63 of AtpE were likely associated with a higher bedaquiline MIC. Five new cases of pre-existing reduced susceptibility to bedaquiline, accompanied by mmpR mutations in most isolates, without a history of bedaquiline treatment were identified. CONCLUSIONS: Bedaquiline treatment leads to an elevated bedaquiline MIC and the acquisition of mmpR and atpE gene mutations in tuberculosis strains. The standardisation of bedaquiline phenotypic susceptibility testing is urgently needed based on observed discrepancies between our study and previous studies and differences in solid and liquid media MIC determinations.