Radiotherapy Leaves a Lasting Inflammatory Signature in the Saliva of Head and Neck Cancer Patients

For the roughly 940,000 people diagnosed with head and neck cancer each year worldwide, radiotherapy is often a lifeline. It is one of the primary treatments for these malignancies, which arise predominantly from the mucosal linings of the oral cavity, pharynx, and larynx, and it is used alone or in combination with surgery and systemic therapies. Yet the same high-energy beams that destroy tumor cells also pass through structures that are exquisitely sensitive to radiation: the salivary glands. When the parotid, submandibular, and sublingual glands are irradiated, their secretory function can decline irreversibly, leaving patients with xerostomia, the profound dry mouth that impairs sleep, speech, swallowing, oral health, and overall quality of life. Artificial saliva and pharmacologic salivary stimulants offer only temporary symptomatic relief, because nothing currently approved reverses the underlying glandular injury and failed regeneration.

A new exploratory study published in Frontiers in Oral Health by researchers at Texas A&M Health Science Center and their collaborators now offers a detailed molecular portrait of what happens inside the mouths of these patients after treatment. The team followed 16 patients with newly diagnosed head and neck cancer, collecting chewing-stimulated whole saliva before radiotherapy and again at one and three months afterward. Using a custom magnetic Luminex assay capable of quantifying 25 cytokines simultaneously, the investigators tracked a broad panel of chemokines, interleukins, growth factors, and other immune signaling molecules. The design allowed each patient to serve as their own control, a powerful approach that reduces the confounding introduced by individual variation in baseline oral health, tumor biology, and immune status.

The first and most clinically immediate finding confirmed what oncologists and dentists have long observed at the chairside: chewing-stimulated saliva flow rates fell significantly in most patients. Twelve of the 16 patients had decreased flow by one month after radiotherapy, and seven of the eight patients who remained in the study at three months showed the same decline. Critically, the drop persisted without significant recovery between the one-month and three-month measurements, underscoring the chronic nature of radiation-induced salivary hypofunction. Because less saliva is produced, the oral environment loses its principal buffering, lubricating, and antimicrobial defense system, setting the stage for radiation-induced dental caries, mucosal discomfort, and secondary infections.

The cytokine analysis, however, is where the study makes its most distinctive contribution. One month after radiotherapy, saliva concentrations of 10 of the 25 measured cytokines had risen significantly compared with baseline. This roster included the chemokines CCL2 and CXCL1, the growth factors M-CSF, HGF, and GDF15, and the pro-inflammatory mediators IL-1α, IL-1β, IL-4, IL-6, and TNFα. By three months, eight of these ten molecules were still elevated, and two additional pro-inflammatory cytokines, GM-CSF and IL-18, had joined the list. Meanwhile, the anti-inflammatory and regulatory cytokines IL-10 and IL-27 showed no significant change, meaning the post-radiotherapy salivary environment tilted decisively toward inflammation rather than resolution.

Interpreting these concentrations required a technical subtlety that matters for anyone working in salivary diagnostics. Because flow rate itself decreased after radiotherapy, a rise in the absolute concentration of a cytokine per milliliter could partly reflect the shrinking volume of saliva rather than increased production by the glands. To account for this, the researchers calculated flow rate-adjusted levels, expressed in picograms per minute, which better approximate the actual cytokine output and immune activity within the salivary tissue. When the data were normalized this way, the picture narrowed: only seven cytokines showed significant increases in secretion rate, and just two of them, CCL2 and GDF15, remained elevated at both one and three months. IL-1β and IL-6 rose only at the one-month mark, while GM-CSF, IL-1α, and IL-18 became elevated only at three months, hinting at a temporal shift from acute inflammatory signaling toward a more chronic phase of glandular stress.

The identities of these persistent molecules are biologically telling. CCL2 and CX3CL1 are chemokines that recruit leukocytes into damaged tissue. IL-1α, IL-1β, IL-4, IL-6, IL-18, and TNFα drive apoptosis, cellular senescence, and inflammatory cascades. M-CSF and GM-CSF govern the differentiation and activation of myeloid cells, including the macrophages that preclinical work has implicated as central players in radiation injury and repair of salivary glands. GDF15 has been linked to the senescence of epithelial and endothelial cells after irradiation, while HGF, which also rose in this cohort, is known to counteract apoptosis and senescence in radiated tissues. The overall profile therefore suggests that irradiated glands are locked in a state of prolonged inflammatory and stress signaling, a molecular echo of the damage that may ultimately drive fibrosis, immune dysfunction, and permanent loss of secretion.

To test whether the human findings reflect events occurring within the glands themselves rather than elsewhere in the body, the team turned to mouse models. Using previously collected RNA samples from mouse submandibular glands at four and thirty days after radiation, they performed quantitative reverse transcription polymerase chain reaction for the cytokines that had changed most clearly in patient saliva. The results were strikingly parallel: mRNA levels of Ccl2, Gdf15, IL1a, IL1b, and IL6 were significantly elevated at both time points after irradiation. Even more encouraging, extracellular vesicles derived from induced pluripotent stem cell-derived mesenchymal stem cells, a regenerative therapy that the group has previously shown to preserve salivary function in mice, suppressed the chronic elevation of these cytokine transcripts by day thirty, with the exception of IL1a. Genes for GM-CSF and IL18, by contrast, were not significantly affected by radiation or by the therapy, mirroring the more variable behavior of those molecules in patients.

This convergence between human saliva and mouse gland tissue carries real translational weight. If salivary cytokine profiles genuinely report on the inflammatory state of the irradiated glands, they could serve as non-invasive biomarkers for predicting which patients will develop severe dry mouth, for stratifying patients toward macrophage-targeting and anti-inflammatory therapies now being explored in preclinical models, and for monitoring whether such interventions are working. Prior studies have already shown that patients with oral cancers carry higher salivary levels of IL-1β, IL-6, IL-8, IL-10, and TNFα than healthy controls, and that recurrence-free survivors treated with radiation, but not surgery alone, show further persistent increases. The new data extend and quantify that signal across a much broader cytokine panel and at matched time points within the same patients.

The authors are careful to frame the work as proof of concept rather than definitive clinical guidance. The cohort was small, limited by funding constraints, and attrition reduced the sample from eighteen patients at baseline to sixteen at one month and only eight at three months. Cytokine concentrations varied widely between individuals and followed lognormal rather than normal distributions, and the researchers did not adjust for multiple comparisons, so the findings are exploratory and descriptive, with P-values to be interpreted cautiously. Validation in larger, multi-center cohorts with longer follow-up will be essential before salivary cytokine profiling can enter routine oncology or dental practice.

Even so, the study opens a concrete path toward a long-standing clinical problem. Radiation-induced dry mouth has resisted decades of symptomatic management because the molecular mechanisms of glandular injury in actual patients have remained poorly characterized. By showing that a panel of pro-inflammatory cytokines rises measurably and persistently in saliva after treatment, that the most robust changes survive correction for reduced flow, and that these same signals appear in animal glands where regenerative therapies can reverse them, the Texas A&M-led team has identified both a potential diagnostic window and a set of therapeutic targets. For the hundreds of thousands of head and neck cancer survivors living with xerostomia, a simple saliva test that reveals the state of their glands, and treatments that quiet the inflammatory storm the beams have unleashed, would represent a transformative advance in survivorship care.

Subject of Research: Salivary cytokine changes in head and neck cancer patients after radiotherapy and their relevance to radiation-induced dry mouth

Article Title: Changes of salivary cytokines in head and neck cancer patients following radiotherapy

Article References: Zhao, Q., Jaiswal, J., Yu, V., Chang, E., Zhang, Y., Mendoza, L., Noureldin, A. A. K., Wang, X., & Liu, F. (2026). Changes of salivary cytokines in head and neck cancer patients following radiotherapy. Frontiers in Oral Health, 7, Article 1969672. https://doi.org/10.3389/froh.2026.1969672

Image Credits: AI Generated

DOI: 10.3389/froh.2026.1969672

Keywords: head and neck cancer, radiotherapy, salivary glands, cytokines, xerostomia, saliva biomarkers, CCL2, GDF15, inflammation, macrophages, extracellular vesicles, radiation-induced dry mouth