Platinum-based chemotherapy remains a mainstay for advanced non‑small cell lung cancer (NSCLC), but intrinsic and acquired resistance limit clinical benefit. JMJD5 (Jumonji Domain-Containing Protein 5) is a multifunctional protein with reported roles in tumor biology and with both enzymatic and non-enzymatic activities. Prior work indicated JMJD5 can modulate sensitivity to EGFR tyrosine kinase inhibitors, but its role in modulating response to conventional platinum chemotherapy such as cisplatin had not been defined.
The study summarized here evaluated the clinical relevance and functional role of JMJD5 in NSCLC chemotherapy response, using patient cohort bioinformatics, in vitro assays in NSCLC cell lines, mechanistic perturbations including an enzymatically inactive mutant, and in vivo xenograft validation.
Clinical relevance was assessed by bioinformatics analysis of patient cohorts to correlate JMJD5 expression with outcomes in chemotherapy-treated NSCLC patients. In vitro functional experiments used human NSCLC cell lines A549 and H1299. Approaches included JMJD5 overexpression modeling, cytotoxicity and colony formation assays, apoptosis measurements, and assessment of DNA damage markers. An enzymatically inactive JMJD5 mutant was introduced to determine whether the observed effects required JMJD5 catalytic activity.
In vivo validation employed nude mouse xenograft models to test whether JMJD5 overexpression altered tumor response to cisplatin treatment. The study compared tumor volume and weight between groups treated with cisplatin alone and those with combined JMJD5 overexpression and cisplatin.
Bioinformatics analysis showed that low JMJD5 expression was associated with poorer overall survival among NSCLC patients who received chemotherapy. Tumor tissue samples demonstrated downregulation of JMJD5 after chemotherapy. In vitro, cisplatin treatment reduced JMJD5 levels in A549 and H1299 cells.
Functionally, restoring JMJD5 expression in these NSCLC cell lines significantly sensitized cells to cisplatin. JMJD5 overexpression enhanced the anti-proliferative effects of cisplatin, decreased colony formation, and increased apoptosis. These phenotypic changes were accompanied by amplified DNA damage, as evidenced by increased levels of γH2A.X, a marker of double-strand DNA breaks.
Crucially, the chemosensitizing effect of JMJD5 did not require its enzymatic activity: an enzymatically inactive JMJD5 mutant retained the ability to enhance cisplatin sensitivity. Mechanistic studies revealed that JMJD5 overexpression suppressed cisplatin-induced phosphorylation of the checkpoint kinases Chk1 and Chk2. This finding indicates that JMJD5 may impair activation of DNA damage checkpoints, thereby permitting accumulation of DNA lesions and promoting apoptosis in the presence of cisplatin.
Taken together, these data support a model in which JMJD5 amplifies cisplatin-induced DNA damage and reduces checkpoint signaling through a non-catalytic mechanism, increasing cytotoxicity in NSCLC cells.
In nude mouse xenograft models, combining JMJD5 overexpression with cisplatin produced markedly greater tumor suppression than cisplatin alone. Tumors in the combination group showed reduced volume and weight compared with those treated with cisplatin only, supporting the in vitro findings that JMJD5 enhances cisplatin efficacy.
The observations suggest that restoring or stabilizing JMJD5 expression could be a strategy to sensitize NSCLC tumors to platinum chemotherapy and to overcome or mitigate platinum resistance. Because the chemosensitizing activity appears to be independent of JMJD5 catalytic function, therapeutic approaches may focus on increasing JMJD5 protein levels or preventing its downregulation rather than targeting its enzymatic activity.
JMJD5 may therefore represent a novel adjunct target for combination with standard cisplatin therapy in NSCLC. Clinical translation would require further validation, including confirmation of prognostic value in larger patient cohorts, detailed pharmacologic or genetic approaches to modulate JMJD5 in vivo, and assessment of safety and off-target effects.
The abstract reports associations and experimental findings but does not provide cohort sizes, specific dosing regimens, timepoints, or statistical metrics; these details were not reported in the source abstract and would require the full text for complete appraisal. Nevertheless, the reported data demonstrate that JMJD5 enhances cisplatin sensitivity in NSCLC by amplifying DNA damage and apoptosis via a non-enzymatic mechanism and that JMJD5 overexpression improves cisplatin efficacy in xenograft models. The authors propose JMJD5 as a potential target to overcome platinum resistance and justify further mechanistic and translational studies.