Optimal Contact Concentration of Paclitaxel in the Collagen Gel Droplet-Embedded Culture Drug Sensitivity Test for Human Oral Squamous Cell Carcinoma and Evaluation of Combination with Cetuximab

Abstract

<b><i>Objective:</i></b> A combination of the taxane anticancer drug paclitaxel (PTX) and molecular target drug cetuximab (cMab) is effective for the treatment of head and neck squamous cell carcinoma (HNSCC). However, its use is associated with serious side effects, such as neuropathy and myelosuppression. In addition, it is administered regardless of patient sensitivity because biomarkers indicating its efficacy are unavailable. Therefore, we investigated the usefulness of setting the indicated contact concentration of PTX and predicted the antitumor effect of combined contact with cMab using the collagen gel droplet-embedded culture drug sensitivity test (CD-DST). <b><i>Method:</i></b> Twelve human oral squamous cell carcinoma (OSCC) cell lines (i.e., SAS, HSC-2, HSC-3, HSC-4, OSC-19, OSC-20, KON, HO-1-N-1, HO-1-u-1, SAT, SCC-4, and Nialym) were used. Using the CD-DST, we calculated the optimal contact concentration of the cells with PTX based on the clinical response rate of HNSCC and evaluated the combined contact with cMab. Furthermore, nude mice were treated with standalone PTX and PTX + cMab, and the results were compared with those of the CD-DST. <b><i>Results:</i></b> Based on the CD-DST, 0.1 μg/mL was the optimal contact concentration of PTX, to which the cells showed dose-dependent sensitivity. Moreover, the CD-DST method was used to evaluate the antitumor effects on OSCC even when PTX was used in combination with cMab. The antitumor effects in the CD-DST and nude mice were correlated (<i>p</i> < 0.05). <b><i>Conclusion:</i></b> The CD-DST results suggested that it was possible to predict the clinical effects of single-contact PTX and the enhancing effect of cMab + PTX.

PTEN Is Activated by the Addition of Cetuximab to Paclitaxel in Oral Squamous Cell Carcinoma

“…Thus, we utilized 3D cultures and assessed the expression of PI3KCA, AKT, and PTEN genes in 3D cultures before and after exposure to cMab and PTX. CD-DST enables long-term 3D cultures that can simulate in vivo conditions and, furthermore, allows exposure to anticancer drugs at the same concentration as in the clinical settings (11,12,14). Ohnishi et al reported that OSCC cell lines grown in monolayers were resistant to cMab, but became sensitive, formed aggregates, and showed activation of the PI3K-AKT pathway when grown as floating cultures (26).…”

“…A total of 90 μl were added per well to a 6-well non-treated plate using a micropipette. The solution mixed with the OSCC cell lines were allowed to make a gel by incubating the plate at 37˚C for 1 h and cultured in DMEM/F-12 (DF) medium containing 10% FBS for 24 h. In accordance with the report from Kii et al (12), cells were exposed to 0.1 μg/ml of PTX for 24 h and, in accordance with the report from Ryuki et al (14), to 250 μg/ml of cMab for 144 h. The anticancer drugs were the removed by washing the plates with phosphate buffered saline (PBS); the media were replaced with serum-free medium and cells were cultured for an additional 6 days. Following this, the cells were stained with neutral red solution for 2 h and fixed in 10% neutral formalin solution for 40 min.…”

“…Comparison of PTEN expression levels in vivo in xenograft tumors: The OSCC cell lines (1×10 7 ) were diluted with 0.5 ml of Hank's solution and administered subcutaneously to the back of nude mice using a 23G Terumo syringe ® ; the 5 cell lines HSC-2, OSC-20, SAS, SAT, and HSC-4 produced engraftments. Anticancer drugs were administered according to the method reported by Kii et al (12) and Harada et al (16) through intraperitoneal injection with PTX (20 mg/kg/day, twice/week, 3 weeks) and/or cMab (20 mg/kg/day, twice/week, 3 weeks). Twenty-one days after the start of anticancer drug administration, nude mice were sacrificed via intraperitoneal administration of somnopentyl (pentobarbital sodium) at 200 mg/kg.…”