Effects of proton versus photon irradiation on (lymph)angiogenic, inflammatory, proliferative and anti-tumor immune responses in head and neck squamous cell carcinoma

Abstract

The proximity of organs at risk makes the treatment of head and neck squamous cell carcinoma (HNSCC) challenging by standard radiotherapy. The higher precision in tumor targeting of proton (P) therapy could promote it as the treatment of choice for HNSCC. Besides the physical advantage in dose deposition, few is known about the biological impact of P versus photons (X) in this setting. To investigate the comparative biological effects of P versus X radiation in HNSCC cells, we assessed the relative biological effectiveness (RBE), viability, proliferation and mRNA levels for genes involved in (lymph)angiogenesis, inflammation, proliferation and anti-tumor immunity. These parameters, particularly VEGF-C protein levels and regulations, were documented in freshly irradiated and/or long-term surviving cells receiving low/high-dose, single (SI)/multiple (MI) irradiations with P/X. The RBE was found to be 1.1 Key (lymph)angiogenesis and inflammation genes were downregulated (except for vegf-c) after P and upregulated after X irradiation in MI surviving cells, demonstrating a more favorable profile after P irradiation. Both irradiation types stimulated vegf-c promoter activity in a NF-κB-dependent transcriptional regulation manner, but at a lesser extent after P, as compared to X irradiation, which correlated with mRNA and protein levels. The cells surviving to MI by P or X generated tumors with higher volume, anarchic architecture and increased density of blood vessels. Increased lymphangiogenesis and a transcriptomic analysis in favor of a more aggressive phenotype were observed in tumors generated with X-irradiated cells. Increased detection of lymphatic vessels in relapsed tumors from patients receiving X radiotherapy was consistent with these findings. This study provides new data about the biological advantage of P, as compared to X irradiation. In addition to its physical advantage in dose deposition, P irradiation may help to improve treatment approaches for HNSCC.

Proton re-irradiation of unresectable recurrent head and neck cancers

“…Bulky tumors (prevailed in our cohort) or CTV>50 cm3 are shown to be associated with higher toxicity and poor outcomes [11,23]. Though, the lower toxicity rate of protons is usually being accounted for in its dose distribution, recent experimental studies reported lower expression of factors involved in lymph-and angiogenesis, in ammation, and immune tolerance [27].…”

Radiation‐induced tumor immunity in patients with non‐small cell lung cancer

“…Lupu‐Plesu et al . recently published results of an in vitro study in head and neck squamous cell carcinoma cells examining the biological effects of proton versus photon RT for genes involved in anti‐tumor autoimmunity, namely PD‐L1, and found that both proton and photon RT augment PD‐L1 mRNA expression in a dose‐dependent manner . Given our limited cohort size, this question should be addressed in future larger studies since no conclusion can be drawn at this time.…”

Three Discipline Collaborative Radiation Therapy (3DCRT) Special Debate: I would treat prostate cancer with proton therapy

“…Further work is needed to implement proton therapy in combination with anti‐angiogenic or anti‐immune checkpoint drugs. It is not clear whether the theoretical benefits of proton beam therapy could be translated into clinically meaningful improvement for prostate cancer patients, so any progress implies an urgent need for prospective randomized clinical trials to measure the toxicity and disease control …”