Head and neck cancer stem cells (CSCs) are highly resistant to treatment. When EGFR is overexpressed in head and neck squamous cell carcinoma (HNSCC), HER2 and HER3 are also expressed. The aim of the present study was to investigate the effect of HER1/2/3 blockade through a combination of cetuximab and pertuzumab, with or without photon irradiation, on the proliferation and migration/invasion capabilities of an HNSCC chemo- and radioresistant human cell line (SQ20B) and its corresponding stem cell subpopulation. Cell proliferation, migration and invasion were studied after treatment with cetuximab +/− pertuzumab +/− 10 Gy photon irradiation. EGFR, phospho-EGFR, HER2 and HER3 protein expression levels were studied. Activation or inhibition of the RAS/MAPK and AKT-mTOR downstream signalling cascades was investigated through phospho-AKT and phospho-MEK1/2 expression. Cetuximab strongly inhibited SQ20B and FaDu cell proliferation, migration and invasion, whereas it had little effect on SQ20B-CSCs. Cetuximab–pertuzumab combined with radiation significantly inhibited SQ20B and FaDu cell and SQ20B-CSC proliferation, migration and invasion. Cetuximab–pertuzumab with 10 Gy photon irradiation switched off both phospho-AKT and phospho-MEK1/2 expression in the three populations. The triple therapy is therefore thought to inhibit SQ20B cells, SQ20B-CSCs and FaDu cells through an AKT-mTOR and Ras-MAPK downstream signalling blockade.

Our work from the five past years has significantly contributed to the advancement of knowledge in the field of carbon ion radiobiology. We demonstrated their superior relative biological effectiveness (RBE) at different levels: - Gene and chromosomal damage induced by carbon irradiation are so complex that they cannot be transmitted in the progeny of irradiated tumor cells, thus limiting genomic instability and improving local control. Chromosome/chromatid loss appears as a specific signature of carbon ion exposure in sensitive and resistant head and neck squamous cell carcinoma (HNSCC) cells (Hanot et al. Plos One, 2012). We also demonstrated that the response to carbon ions is independent of the telomeres’ size. The presence of long telomeres in tumor cells of patients with glioblastoma is a well-known factor of poor prognosis as they become more resistant to oxidative stress induced by conventional radiotherapy. Thus, our data first underlines that patients with long telomeres can advantageously benefit from carbon-therapy (Ferrandon et al., Mol Neurobiol, 2013). - Cell death is triggered earlier and more significantly by carbon ions in HNSCC or glioblastoma cellular models. It involves either early apoptosis in radiosensitive cells or mitotic catastrophe followed by late apoptosis in radioresistant ones. Apoptosis is activated through a pathway independent of p53, but dependent on ceramide (a lipid signaling mediator) (Alphonse et al, BMC Cancer, 2013; Ferrandon et al., Cancer Letters, 2015), giving carbon ions a significant advantage since 50% of tumors have a mutated p53 gene. - Carbon ions are more effective than photons in killing cancer stem cells (CSCs) in HNSCC. Their association with cell cycle arrest inhibitors or gadolinium-based nanoparticles also increases the efficiency of therapeutic response (Bertrand et al., Stem Cell Rev, 2014; in preparation). Furthermore, molecular connections between the stem-cell state and epithelio-mesenchymal transition (EMT) program have recently emerged, pointing out a double danger for cancer patients since CSCs have the ability to renew indefinitely and are resistant to apoptosis. Our last investigations point out a significant decrease in the migration and invasion of both parental and CSC populations irradiated with carbon ions, thus highlighting the great interest of carbon-therapy in the prevention of recurrences and metastases. Supported by LabEx PRIMES ANR-11-LABX-0063/ANR-11-IDEX-0007, France Hadron ANR-11-INBS-0007, Lyric and CPER ETOILE

La radiothérapie est au centre de la prise en charge des cancers ORL. L’évolution technologique de ces dernières années, avec l’émergence de la radiothérapie par modulation d’intensité, a permis de lui attribuer un rôle majeur dans la prise en charge. Il persiste cependant de nombreuses récidives à la fois locales et locorégionales qui soulignent l’existence de mécanismes biologiques de résistance au traitement. De la cellule elle-même, sa capacité de réparation et de prolifération, son microenvironnement et ses conditions d’oxygénation, ses capacités migratoires et invasives, jusqu’aux paramètres biologiques liés au patient, il existe de nombreux mécanismes impliquant la radiosensibilité et/ou radiorésistance des cancers ORL. Cette étude s’attache à explorer les principaux mécanismes biologiques impliqués dans la radiorésistance des cellules tumorales de cancer ORL et de décrire les pistes thérapeutiques prometteuses dans cette pathologie.

Head and neck squamous cell cancer (HNSCC) is the sixth most common cancer in the world.Effective therapeutic modalities such as surgery, radiation, chemotherapy and combinations of each are used in the management of the disease.In most cases, treatment fails to obtain total cancer cure.In recent years, it appears that one of the key determinants of treatment failure may be the presence of cancer stem cells (CSCs) that escape currently available therapies.CSCs form a small portion of the total tumor burden but may play a disproportionately important role in determining outcomes.CSCs have stem features such as self-renewal, high migration capacity, drug resistance, high proliferation abilities.A large body of evidence points to the fact that CSCs are particularly resistant to radiotherapy and chemotherapy.In HNSCC, CSCs have been increasingly shown to have an integral role in tumor initiation, disease progression, metastasis and treatment resistance.In the light of such observations, the present review summarizes biological characteristics of CSCs in HNSCC, outlines targeted strategies for the successful eradication of CSCs in HNSCC including targeting the self-renewal controlling pathways, blocking epithelial mesenchymal transition, niche targeting, immunotherapy approaches and highlights the need to better understand CSCs biology for new treatments modalities.

[This corrects the article on p. 58 in vol. 6, PMID: 27014633.].

Radiation therapy is a cornerstone of head and neck cancer management. Technological improvements in recent years in radiation therapy, with intensity-modulated techniques, reinforce even more its role. However, both local and locoregional relapses are still observed. Understanding biological mechanisms of treatment resistance is a topic of major interest. From the cancer cell itself, its ability to repair and proliferate, its microenvironment and oxygenation conditions, migratory and invasive capacity, to biological parameters related to the patient, there are many mechanisms involving radiosensitivity and/or radioresistance of head and neck cancer. The present study explores the main biological mechanisms involved in radiation resistance of head and neck cancer, and describes promising therapeutic approaches.

Recent evidences suggest that many types of cancers contain a cell population presenting stem cell properties. While the great majority of tumor cells are destined to differentiate, and eventually stop dividing, only a minority population of cells, termed cancer stem cells (CSCs), possesses extensive self-renewal capability and can recapitulate tumor pathophysiology in an immune-compromised animal model. Tumor initiating cells have been identified and isolated in many tumor types including brain, colon and prostate. They are virtually resistant to radiation and may contribute to treatment resistance and recurrence. Therefore, therapies specifically targeting CSCs will likely be needed for complete tumor eradication. The present study reviews published reports identifying the mechanisms of radioresistance of CSCs and potential targets based on the pathways of self-renewal. Further elucidation of pathways that regulate CSCs may provide insights into the development of novel innovative therapies.

Head and neck squamous cell carcinoma (HNSCC) is an aggressive and recurrent malignancy owing to intrinsic radioresistance and lack of apoptosis induction. Several strategies aiming at radiosensitizing these tumors are currently being developed, one of which relies on the use of high Z elements nanoparticles such as gadolinium. Ultrasmall (5nm) gadolinium-based nanoparticles (GBNs) display properties, including stability, lack of toxicity, renal elimination, preferential accumulation in tumors (EPR effect) which make them a promising radiosensitizing tool. Once delivered to the tumor, GBNs amplify the efficacy of radiotherapy through the generation of secondary electrons leading to the overproduction of reactive oxygen species (ROS).