CD98hc a potential biomarker for therapy outcome and a putative therapeutical target for radiosensitization of head and neck squamous cell carcinoma


CD98hc a potential biomarker for therapy outcome and a putative therapeutical target for radiosensitization of head and neck squamous cell carcinoma

Digomann, D.; Kurth, I.; Linge, A.; Hein, L.; Heiden, S.; Baumann, M.; Dubrovska, A.

Retrospective analyses of CSC-related biomarkers followed by prospective validation studies in patients with locally advanced HNSCC are currently being performed in an ongoing multicentre retrospective – prospective trial conducted by the Radiation Oncology Group of the German Cancer Consortium (DKTK-ROG) For the patients with locally advanced head and neck squamous cell carcinoma (HNSCC) treated with a curatively intended cisplatin-based postoperative radiochemotherapy or primary radiochemotherapy, the expression level of SLC3A2 (Solute Carrier Family 3 member 2), a putative cancer stem cell marker was positively correlated with poor locoregional control in locally advanced (HNSCC) [1, 2].
The human gene SLC3A2 encodes the heavy chain of CD98; a ~125 kDa heterodimeric L-type amino acid transporter. CD98hc also interacts with integrin β subunit and has a putative role in regulating integrin signaling, which controls cell proliferation, survival, migration, and epithelial adhesion [3].
The aim of this study is to elucidate the potential role of stem cell marker CD98hc in regulation of the HNSCC radiosensitivity.
The expression levels of CD98 in nine HNSCC cell lines measured by western blot analysis and flow cytometry were positively correlated with their respective in vivo tumor control dose 50 (TCD50) values (ref). An increase of CD98hc expression was also detected by Western blotting in the radioresistant derivatives of the established HNSCC cells as compared to their parental counterparts. In addition, expression of CD98hs was induced in the parental HNSCC cells after single dose irradiation of HNSCC cells with 4Gy of X-ray.
To analyze a functional role of CD98hc in the regulation of HNSCC radioresistance, SLC3A2 (gene of CD98hc) was knocked down via siRNA in Cal33, Fadu, UT5 and SAS cells, which then were subjected to the radiobiological colony formation assays. A knockdown of SLC3A2 in HNSCC cells followed by irradiation decreased the capability for colony formation compared to the cells transfected with scrambled siRNA.
For further in vitro and in vivo experiments, cell lines with a low CD98hc level were established using CRISPR/Cas9 technology. Off-targets were reduced using a modified CRISPR/Cas9-variant that was confirmed by PCR and sequencing experiments.
In addition, a recombinant neutralizing antibody against CD98hc is currently tested as possible CD98hc targeted and radiosensitizing therapy.
Finally, publicly available TCGA-gene dataset for HNSCC patients treated with and without radiotherapy was used to analyze a potential correlation of SLC3A2 expression with expression of other genes and clinical outcome of the HNSCC patients.
The results support the hypothesis that CD98hc is playing a role in the regulation of HNSCC radioresistance. In the future CD98hc may be used as a prognostic marker and become a potential target for combined radiochemotherapy in locally advanced HNSCC.

References:

[1] Linge, A., Lock, S., Gudziol, V., Nowak, A., Lohaus, F., von Neubeck, C., Jutz, M., Abdollahi, A.,
Debus, J., Tinhofer, I., et al. (2016). Low CSC marker expression and low hypoxia identify good
prognosis subgroups in HPV(-)HNSCC after postoperative radiochemotherapy: a multicenter study
of the DKTK-ROG. Clin. Cancer Res.
[2]. https://www.ncbi.nlm.nih.gov/pubmed/27913065
[3]Cantor, J.M., Ginsberg, M.H., 2012. CD98 at the crossroads of adaptive immunity and cancer. J Cell Sci 125, 1373–1382. doi:10.1242/jcs.096040

Keywords: CD98; HNSCC; Radioresistance

  • Contribution to proceedings
    DEGRO Akademie: 26. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 09.-11.02.2017, Universitätsklinikum Tübingen, Deutschland
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 192(2016)Suppl.1, 124

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Publ.-Id: 25114