Abstract
(1) Background: For advanced head and neck squamous cell carcinoma (HNSCC), boron neutron capture therapy (BNCT) is a potential therapeutic option, but high concentrations of boron within HNSCC are necessary. Therefore, this in vitro pilot study examined the uptake and concentration of boron in HNSCC cells using the trans-stimulation effect of L-tyrosine when compared to non-stimulated samples. (2) Methods: Two HNSCC cell lines were incubated with L-tyrosine for up to two hours, followed by incubation with three L-para-boronophenylalanine (BPA) concentrations (5, 20, 50 ppm) at eight incubation times (1–4.5 h in half-hour steps). Subsequently, cellular boron uptake was measured via inductively coupled plasma mass spectrometry. (3) Results: No differences between laryngeal and oral SCC cells were seen; therefore, data were pooled. In total, boron uptake was not significantly increased in trans-stimulated samples when compared to the control group (all p > 0.05). Nevertheless, with trans-stimulation, higher BPA concentrations resulted in higher intracellular boron concentrations (5 < 20 < 50 ppm; all: p < 0.05), whereas these differences were less distinct in the non-trans-stimulated group. (4) Conclusions: The effect of trans-stimulation for up to two hours seems to be less relevant for HNSCC, though trans-stimulated HNSCC cells seem to have a more distinct BPA-dose-dependent cellular boron uptake that might be addressed in further research.
Highlights
Head and neck cancer—with about 90% squamous cell carcinoma (HNSCC)—accounts for 3% of all cancer types, with an incidence of about 900,000 new cases and 500,000 deaths per year [1]
(4) Conclusions: The effect of trans-stimulation for up to two hours seems to be less relevant for head and neck squamous cell carcinoma (HNSCC), though trans-stimulated HNSCC cells seem to have a more distinct BPA-dose-dependent cellular boron uptake that might be addressed in further research
It can be seen that the amount of LAT-1 for healthy oral cells such as Human oral keratinocytes (HOK) and pooled human gingival epithelial cells (pHGEP) is lower than for those of the tumour cell lines PCI 1 and PC5I o1f39
Summary
Head and neck cancer—with about 90% squamous cell carcinoma (HNSCC)—accounts for 3% of all cancer types, with an incidence of about 900,000 new cases and 500,000 deaths per year [1]. For advanced as well as metastatic HNSCC, additional treatment options are needed. One of these therapies could be boron neutron capture therapy (BNCT), which is based on the reaction of the non-radioactive boron-10 with low-energy (thermal) neutrons, resulting in the nuclear reaction 10B(n,α)7Li. Because of the short range of the produced alpha particles and lithium from about 8–10 μm with a high linear energy transfer, the radiation effects mainly occur in cells containing boron [2]. A boron carrier such as mercaptoundecahydrocloso-dodecaborate (BSH) or L-para-boronophenylalanine (BPA), a modified amino acid, is infused in a fructose solution into a peripheral vein, resulting in a higher uptake of the 10B carrier in cancerous tissue as tumour cells have a higher turnover with an increased energy consumption [4,5]. Whereas the expression of LAT-1 in normal mucosa is low [8], it increases in cases of HNSCC and decreases for the highest dedifferentiation levels [9]
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