Lung cancer is the second most common cancer in the world and has the highest mortality rate [1,2]. NSCLC represents approximately 85 % of all lung malignancies, with adenocarcinoma being the most common histological subtype [2,3]. Radiotherapy, either for curative or palliative purposes, occupies a pivotal position in comprehensive disease management strategies of lung adenocarcinoma [[4], [5], [6], [7]]. However, loco-regional recurrence or metastatic spread due to resistance occurs inevitably in patients undergoing irradiation therapy or combination treatments, thus significantly limiting the therapeutic effectiveness [8].

The tumor microenvironment (TME) plays a crucial role in enabling tumor cells to survive death-inducing stimuli. As the most dominant component in TME, Cancer-associated fibroblasts (CAFs) have powerful functions in promoting tumor angiogenesis, ECM degradation, drug resistance and immunosuppression [[9], [10], [11], [12], [13], [14]]. Preclinical investigations indicate that the activation of fibroblasts initially serves as a component of the host response and defense mechanism, nevertheless, in the context of the tumor, it may confer therapy resistance [15,16]. For example, CAFs were found to promote chemo-resistance in breast and lung cancer patients via the sustenance of cancer stemness [17]. Cytokines secreted by fibroblasts were found to be associated with tumor progression and mediate immune resistance as well as chemo-resistance in a variety of tumors, including NSCLC [[18], [19], [20], [21], [22]]. It has been reported that irradiation can directly induce CAFs to fall into a senescence like state or alter the transcription and secretion profile of CAFs in NSCLC [11,[23], [24], [25], [26], [27]]. Alternatively, there are also literature reports indicating that CAFs can indirectly induce the irradiation resistance of tumor cells through paracrine signaling or the remodeling of the tumor microenvironment after irradiation [[28], [29], [30], [31], [32]]. Therefore, a thorough investigation of CAFs and their interaction mechanisms with the TME holds significant clinical value for understanding therapy resistance and improving the efficacy of radiotherapy in NSCLC.

Radiotherapy uses high-energy rays to damage the DNA of tumor cells, inducing cell apoptosis or necrosis [33]. During this process, high-mobility group protein 1 (HMGB1) is released from damaged tumor cells and functions as a damage-associated molecular pattern (DAMP) protein, which then mediates early inflammation-related responses through interactions with pattern recognition receptors [[34], [35], [36]]. Studies have shown that the early release of HMGB1 induced by anti-tumor therapies (including radiotherapy and immunotherapy) helps activate the body's anti-tumor immune response [37,38]. Therefore, HMGB1 has been extensively explored as a potential biomarker for evaluating early treatment responses in patients. However, further research has revealed that HMGB1 also has detrimental effects: it can promote tumor cell survival through autophagy, enabling tumor cells to evade therapy-induced damage, and mediate remodeling of the immune microenvironment [[39], [40], [41]]. Therefore, continuously elevated levels of HMGB1 in the late stages of treatment are often associated with therapeutic resistance and disease progression, indicating a poor prognosis for patients. For example, clinical studies have shown that high concentrations of HMGB1 in patients with advanced NSCLC frequently correlate with shorter overall survival [39,42]. Blocking the release and activity of HMGB1 has been successful in a wide range of preclinical inflammatory disease models, including NSCLC [43]. Therefore, in-depth investigation of the interaction and underlying mechanisms between altered HMGB1 levels following radiotherapy and treatment resistance may offer novel insights into effective therapeutic strategies for NSCLC.

Given that both HMGB1 and CAFs have been identified as potential biomarkers of therapeutic response, we hypothesized an interaction between these two factors contributing to radiotherapy resistance in NSCLC. For the first time, this study demonstrates a notable synchronization between HMGB1 release from irradiated lung adenocarcinoma cells and the activation of fibroblasts within the tumor microenvironment. Mechanistically, tumor-derived HMGB1 was shown to enhance fibroblast migration and proliferation through activation of the TLR4/PI3K/AKT signaling pathway. Furthermore, HMGB1 released from tumor cells potentially reshapes the immune microenvironment and modulates CAFs subtypes, significantly influencing therapeutic responses to radiotherapy in NSCLC. To validate this, we developed a DPG-RGDLipo nano-delivery system capable of specifically targeting and eliminating HMGB1 in the TME. This approach effectively reversed radiotherapy-induced immunosuppression, subsequently enhancing the radio-sensitivity of lung cancer. Our results demonstrated that HMGB1 inhibition not only suppressed CAFs activation and improved radiotherapy efficacy but also promoted immune infiltration, including CD8+ T cells and dendritic cells (DCs). Moreover, reductions in matrix metalloproteinases 2 (MMP2) and VEGF expression within tumor tissues further highlighted the potential of this combined targeting strategy to inhibit tumor invasion and metastasis. Collectively, this study uncovers a novel interaction between irradiated tumor cells and CAFs, emphasizing the pivotal role of tumor-derived HMGB1 in regulating CAFs phenotypic transitions following radiotherapy. Importantly, these findings propose targeting tumor-derived HMGB1 as a promising therapeutic paradigm to overcome radiotherapy resistance in lung adenocarcinoma.