Cancer Gene Duo Reveals Why Head and Neck Tumors Shrug Off Cisplatin

Head and neck squamous cell carcinoma, the sixth most common cancer worldwide, continues to defy oncologists with an outlook that has barely improved in decades. For patients with advanced disease, cisplatin-based chemotherapy remains a cornerstone of treatment, yet tumors frequently either fail to respond from the outset or acquire resistance during therapy, leaving clinicians with few options. Now, a team of researchers based at Qilu Hospital of Shandong University and collaborating institutions across China has traced a molecular chain of command that appears to drive both the aggressive growth of these tumors and their ability to withstand one of medicine’s oldest platinum drugs. Their work, published as an open-access original article in Cellular and Molecular Life Sciences, points to a two-gene axis, SERPINE1 and CA9, as a potential Achilles heel in a cancer that urgently needs new molecular targets.

The study began with a systematic survey. Rather than focusing on a single candidate gene, the researchers profiled the entire serpin family of genes in head and neck squamous cell carcinoma using data from The Cancer Genome Atlas, the large-scale international effort that has catalogued genomic and clinical information from thousands of tumor specimens. Among the members of this family, best known for proteins that regulate protease activity in blood clotting and tissue remodeling, one gene stood out: SERPINE1, which encodes plasminogen activator inhibitor-1, a secreted protein previously implicated in tumor invasion and metastatic spread in multiple cancer types. Elevated SERPINE1 expression correlated with poor outcomes, making it the primary gene of interest for the team led by corresponding author Dapeng Lei.

To move from correlation to causation, the researchers built laboratory models in which SERPINE1 was either stably silenced or artificially overexpressed in head and neck cancer cell lines. The functional consequences were unambiguous. Cells stripped of SERPINE1 proliferated more slowly, migrated less efficiently across wound surfaces, and showed a markedly reduced capacity to invade through extracellular matrix, the biological hallmark that distinguishes an in situ lesion from a truly dangerous carcinoma. Conversely, cells engineered to produce excess SERPINE1 displayed enhanced versions of all three malignant behaviors. The team then extended these in vitro findings into living animals by transplanting the manipulated cells subcutaneously into immunodeficient nude mice, where the growth differences between SERPINE1-high and SERPINE1-low tumors could be observed directly.

With the oncogenic role of SERPINE1 established, the central question became mechanistic: through which downstream genes does this protein exert its effects? The researchers turned to transcriptome sequencing, an unbiased approach that measures the activity of every gene in the genome simultaneously. Comparing the transcriptional landscapes of SERPINE1-depleted cells against controls, they identified carbonic anhydrase 9, abbreviated CA9, as a key effector. CA9 encodes a membrane-spanning enzyme that catalyzes the reversible hydration of carbon dioxide to bicarbonate and protons, a reaction central to pH regulation. The enzyme is famously hypoxia-inducible, driven by HIF-1 transcriptional activity in oxygen-starved tumor regions, and it helps cancer cells maintain an alkaline intracellular environment while acidifying their surroundings, a shift that promotes invasion and blunts the efficacy of weakly alkaline chemotherapeutics.

The connection between SERPINE1 and CA9 proved especially consequential in the context of cisplatin treatment. To study drug resistance rigorously, the team generated cisplatin-resistant derivatives of two head and neck cancer cell lines, designated FaDu-CDDP and Tu686-CDDP, by exposing the parental cells to escalating doses of the drug. In these resistant populations, both SERPINE1 and CA9 were found to be upregulated in tandem, suggesting that the resistant phenotype travels along the same regulatory axis identified in the sequencing data. Quantitative measurements of the half-maximal inhibitory concentration, or IC50, confirmed that the resistant lines required substantially more cisplatin to achieve the same degree of cell killing, validating the model system before any genetic perturbations were attempted.

The rescue experiments that followed constitute the most technically decisive portion of the study. When the researchers silenced SERPINE1 in the resistant cells, the cells regained sensitivity to cisplatin, and silencing CA9 produced the same effect, indicating that either node of the axis could be targeted to weaken drug resistance. The critical test came next: in SERPINE1-depleted cells, the team restored CA9 expression. Remarkably, this single intervention reversed the suppressive phenotypes caused by SERPINE1 loss, reinstating both the aggressive growth characteristics and, crucially, the resistance to cisplatin. In the logic of molecular biology, such rescue experiments are the gold standard for demonstrating that a downstream gene is not merely a correlate but a functional mediator, and the results placed CA9 squarely in that role, operating downstream of SERPINE1 to execute its effects on tumor behavior and drug response.

The findings carry significant weight for a cancer type in which effective molecular targets remain frustratingly scarce. Unlike lung cancer, where EGFR mutations and ALK rearrangements have spawned a generation of targeted therapies, head and neck squamous cell carcinoma has seen relatively few successes in precision oncology, with anti-PD-1 immunotherapy representing one of the few meaningful advances in recent years. A biomarker axis that simultaneously predicts prognosis and dictates sensitivity to a widely used chemotherapy drug would fill a genuine clinical void. If SERPINE1 and CA9 expression levels can stratify patients at diagnosis, oncologists might one day identify which individuals are likely to benefit from cisplatin and which should be routed toward alternative regimens or clinical trials of combination therapies designed to disrupt the axis itself.

There are also therapeutic implications embedded in the biology of the two proteins. CA9 has long attracted pharmaceutical interest because of its accessibility on the cell surface and its well-characterized enzymatic active site, and several carbonic anhydrase IX inhibitors have progressed through preclinical development, some investigated in combination with standard chemoradiation. The new data suggest that such inhibitors could be particularly valuable in tumors with high SERPINE1 expression, where CA9 acts as the functional conduit for both malignancy and cisplatin resistance. SERPINE1 itself, as a secreted serine protease inhibitor, presents a different but not insurmountable drug development challenge, and small-molecule and biologic approaches to blocking plasminogen activator inhibitor-1 have been explored in other disease contexts, including fibrosis and cardiovascular pathology.

The study also illustrates the power of a multi-layered research design that moves from population-level genomics through engineered cell models to animal xenografts and mechanistic rescue experiments. By anchoring their analysis in TCGA data, the researchers ensured that their candidate gene was relevant to real patient tumors rather than an artifact of cell culture. By deploying two independent cisplatin-resistant cell lines, FaDu and Tu686, they guarded against conclusions that might hold true for only a single genetic background. The work received funding from the National Natural Science Foundation of China and provincial science programs in Shandong, and it was approved by the institutional ethics committees for both the human tissue analyses and the animal procedures, with the authors declaring no competing interests.

Caveats remain, as they always do in translational cancer research. The mechanistic chain was established in cell lines and mouse xenografts, and the abstract does not report clinical trial data demonstrating that SERPINE1 or CA9 levels predict cisplatin response in actual patient cohorts, an essential step before any biomarker enters routine practice. The precise molecular circuitry connecting SERPINE1, a secreted protease inhibitor, to CA9, a hypoxia-responsive metabolic enzyme, also invites further dissection, since the intermediate signaling steps likely involve pathways at the interface of tumor metabolism and stress adaptation. Nevertheless, the demonstration that a single axis governs both tumor progression and chemotherapy resistance in head and neck squamous cell carcinoma offers a coherent framework for future studies, and it revives attention to carbonic anhydrase IX as a vulnerability that may be exploitable precisely at the moment when cisplatin’s effectiveness is faltering. For patients facing a diagnosis with an unfavorable prognosis and limited targeted options, that convergence of growth and resistance in one druggable pathway is a lead worth chasing.

Subject of Research: The SERPINE1–CA9 axis driving progression and cisplatin resistance in head and neck squamous cell carcinoma

Article Title: SERPINE1 promotes HNSCC progression and cisplatin resistance by upregulating CA9

Article References: Wang, S., Chang, F., Peng, T., Li, Z., Wang, Y., Duan, C., Wu, K., Wang, H., Wei, D., Li, W., Qian, Y., Cao, S., Wang, Y., Liu, J., Fang, J., Chen, L., Zhao, J., & Lei, D. (2026). SERPINE1 promotes HNSCC progression and cisplatin resistance by upregulating CA9. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06439-z

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06439-z

Keywords: HNSCC, SERPINE1, CA9, carbonic anhydrase IX, cisplatin resistance, tumor progression, drug resistance, TCGA, xenograft, hypoxia, biomarker, molecular oncology