The research, led by Biswajit Dey and Santosh Kumar Guru at the National Institute of Pharmaceutical Education and Research in Hyderabad, India, together with colleagues at Sambalpur University and other Indian institutions, focused on an enzyme called glutamate dehydrogenase 1, or GDH1. This enzyme sits at a critical junction of cellular metabolism, where it converts glutamate, the breakdown product of the amino acid glutamine, into alpha-ketoglutarate, a molecule that feeds directly into the Krebs cycle inside mitochondria. In doing so, GDH1 performs what biologists call an anaplerotic function: it replenishes the intermediates that the Krebs cycle constantly consumes, keeping the mitochondrial engine running. The new work shows that persister cells in triple-negative breast cancer lean heavily on this engine, and that without it, they simply cannot survive.

Triple-negative breast cancer is defined by the absence of the three molecular targets that modern therapy exploits most effectively: the estrogen receptor, the progesterone receptor, and the HER2 protein. Because none of these handles exist for drugs to grab, patients with this subtype rely almost entirely on chemotherapy, which makes the emergence of drug-tolerant persister cells a particularly dangerous problem. The Indian team began by mining publicly available clinical datasets and found that breast cancer patients with elevated GDH1 expression had significantly worse prognoses. That epidemiological clue set the stage for a detailed mechanistic investigation into what GDH1 actually does inside cells that have just survived a chemotherapeutic hit.

Using laboratory models of triple-negative breast cancer, the researchers generated persister cells by exposing them to chemotherapy and isolating the survivors. Multiple independent techniques then converged on the same conclusion. Western blotting and quantitative reverse-transcription polymerase chain reaction showed that GDH1 protein and messenger RNA were both upregulated in the persister population. Immunofluorescence microscopy visualized the increased enzyme directly inside the surviving cells, and mass spectrometry provided an unbiased proteomic confirmation. Extracellular flux assays, which measure the real-time oxygen consumption and acidification of living cells, revealed that this GDH1 surge came with a shift in mitochondrial metabolism, indicating that the persisters were not merely idle survivors but metabolically reprogrammed cells actively burning glutamine-derived fuel.

The functional consequences of this reprogramming were striking. When the team measured cell viability and migratory capacity, GDH1-high persister cells proved both hardier and more mobile than their non-persister counterparts. Wound healing assays, a standard test of cell migration, showed that the persister cells closed scratches faster, a behavior consistent with the acquisition of invasive traits. Conversely, when the researchers suppressed GDH1, either pharmacologically or through genetic silencing, cell viability dropped and migration slowed. The enzyme was not a passive marker of the persister state; it was actively maintaining it.

One of the most intriguing aspects of the study concerns the physical architecture of mitochondria. Mitochondria are dynamic organelles that constantly fuse and split, and the balance between these two processes shapes their function. The researchers found that GDH1 supports a program of fusion-associated remodeling in persister cells, involving the mitofusin proteins MFN1 and MFN2, which tether neighboring mitochondria together, and the phosphorylation state of dynamin-related protein 1, or DRP1, the master regulator of mitochondrial fission. Specifically, the persister cells showed evidence of increased phosphorylation of DRP1 at serine 637, a modification that inhibits fission and favors elongated, fused mitochondrial networks. This fused state is thought to protect mitochondria during stress, preserving their integrity and their capacity to generate energy when the cell is under attack from chemotherapy. In other words, GDH1 appears to coordinate two survival strategies at once: it supplies the metabolic substrate that keeps the Krebs cycle turning, and it shapes the mitochondrial network into a configuration that is more resilient to damage.

The study also connected GDH1 to epithelial-to-mesenchymal transition, or EMT, the developmental program through which epithelial cancer cells abandon their anchored, orderly identity and adopt the mobile, invasive character of mesenchymal cells. EMT is closely associated with drug tolerance, because the transition suppresses proliferation and activates survival pathways, exactly the phenotype that persister cells display. When the researchers stably knocked down GDH1, they found that EMT markers diminished and the cells lost their ability to form the persister state in the first place. This suggests that GDH1 is not merely a consequence of EMT but an enabler of it, linking glutamine metabolism to the transcriptional and structural changes that allow cancer cells to hunker down under therapy.

Perhaps the most clinically significant experiments came from the animal studies. The team implanted triple-negative breast cancer cells into mice as xenografts and compared tumors with normal GDH1 levels to tumors in which GDH1 had been knocked down. When chemotherapy was administered, the GDH1-deficient tumors responded far more dramatically, demonstrating that removing the enzyme restored chemosensitivity in vivo. Analysis of the tumor tissue showed reduced levels of Ki-67 and PCNA, two well-established markers of cell proliferation, confirming that GDH1 loss impaired the growth machinery of the tumor. Together, these results elevate GDH1 from an interesting biochemical observation to a validated therapeutic target whose inhibition could sensitize tumors to existing drugs.

An important nuance emerged when the researchers followed persister cells over time. After thirty days without drug exposure, GDH1 expression declined back toward baseline, indicating that the enzyme plays a transient, state-dependent role rather than causing a permanent genetic change. This reversibility is characteristic of the non-genetic mechanisms that underpin drug tolerance, and it explains why persister cells can eventually exit their dormant state and resume rapid proliferation, seeding recurrence. It also suggests a therapeutic window: if clinicians could target GDH1 during the period when it is elevated, they might eliminate persisters before they revert to a proliferative, treatment-resistant state.

The implications for patients are considerable. Combination strategies that pair conventional chemotherapy with GDH1 inhibition could, in principle, prevent the establishment of the persister reservoir that so often leads to relapse in triple-negative breast cancer. Because GDH1 acts on both metabolism and mitochondrial dynamics, inhibitors of the enzyme might be particularly effective in tumors that have already adopted a glutamine-dependent survival mode. The work also adds to a growing appreciation that cancer therapy must target not only the dividing cells that dominate a tumor’s bulk but also the quiet, metabolically rewired survivors that hide among them. As the authors conclude, GDH1 stands out as a crucial regulator of persister survival, and drugs aimed at this mitochondrial gatekeeper may represent a promising path toward overcoming chemoresistance in one of breast cancer’s most feared forms.

Subject of Research: Role of glutamate dehydrogenase 1 in the survival of drug-tolerant persister cells in triple-negative breast cancer

Article Title: Glutamate dehydrogenase 1 (GDH1) sustains triple-negative breast cancer persister cell survival by coordinating mitochondrial fusion and anaplerotic flux

Article References: Dey, B., Chatterjee, E., Pandey, N., Singh, H., Basak, S., Kumar, R., Sharma, A., Bhalerao, H. A., Dharavath, A., S., S. L., Singh, P. K., Sonti, R., Naik, P. K., Doijad, N., & Guru, S. K. (2026). Glutamate dehydrogenase 1 (GDH1) sustains triple-negative breast cancer persister cell survival by coordinating mitochondrial fusion and anaplerotic flux. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06316-9

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06316-9

Keywords: triple-negative breast cancer, GDH1, drug-tolerant persister cells, mitochondrial fusion, anaplerotic flux, glutaminolysis, EMT, chemoresistance, cancer metabolism, MFN2, DRP1, tumor recurrence

The pathway in question is the hepatocyte growth factor (HGF)/c-MET axis, a receptor tyrosine kinase system that normally orchestrates embryonic development, tissue regeneration, and wound healing. In cancer, it is hijacked. Overexpression of c-MET has been documented in more than eighty percent of HNSCC cases and correlates with poor prognosis, and the pathway is implicated in resistance to EGFR-targeted drugs such as cetuximab. Earlier work from the same group had already shown that HGF stimulation ramps up glycolysis—the glucose-fermenting Warburg metabolism familiar from textbook cancer biology—in head and neck cancer cells. What remained unknown was whether the same signal also governs glutamine metabolism, the second great nutrient stream on which proliferating tumors depend.

Glutamine is far more than a backup fuel. For rapidly dividing cells it supplies both carbon and nitrogen for building nucleotides, amino acids, and lipids. The gatekeeper of this economy is glutaminase 1, or GLS-1, the rate-limiting enzyme that converts glutamine into glutamate, thereby feeding the tricarboxylic acid cycle and powering mitochondrial energy production. Elevated GLS-1 has been tied to aggressive behavior and poor outcomes in multiple cancer types. The Würzburg-led team, including first author Marius Hörner and senior author Stefan Hartmann, reasoned that if c-MET could commandeer glucose handling, it might also pull the levers of glutaminolysis—and that the connection could be exploitable.

To find out, the researchers compared basal GLS-1 levels in primary human oral keratinocytes—the non-malignant controls—with three HNSCC cell lines of distinct MET status: MET-amplified Detroit 562, originally derived from a pleural metastasis of a pharyngeal carcinoma, and the MET wild-type lines FaDu and SCC-154. The result was unambiguous. Every cancer line expressed more GLS-1 than normal keratinocytes, and the MET-amplified Detroit 562 cells showed the strongest basal expression. When the cells were bathed in recombinant HGF for twenty-four hours, only Detroit 562 responded dramatically: GLS-1 mRNA surged approximately 3.4-fold above control, and GLS-1 protein climbed several-fold on Western blot. FaDu and SCC-154 cells, lacking MET amplification, barely blinked. The metabolic reprogramming, in other words, was selective for cells with an amplified receptor.

The selectivity proved mechanistically decisive. Pretreating Detroit 562 cells with Foretinib, a selective c-MET inhibitor, completely abolished the HGF-driven rise in GLS-1, restoring expression to baseline, while the inhibitor alone left basal levels untouched. Functional assays tracked the metabolic consequences in the culture medium itself. After HGF stimulation, extracellular glutamine concentrations dropped significantly—evidence of increased consumption—while extracellular glutamate rose sharply, consistent with accelerated glutaminolysis. Foretinib prevented both changes, pinning the flux shift squarely on c-MET activity. For a cell line already prone to metastatic behavior, the growth factor was effectively upgrading its metabolic engine.

Next came the question of which intracellular cascade transmits the signal. Based on the group’s prior glucose-metabolism work, in which neither PI3K/AKT nor JAK/STAT contributed to the metabolic switch, attention turned to MAPK/ERK. The bet paid off. HGF triggered robust phosphorylation of ERK1/2 at Tyr204 in Detroit 562 cells, and the selective ERK1/2 inhibitor FR180204 completely blocked the HGF-induced increase in GLS-1 at both mRNA and protein levels. The signaling logic was thus clean: HGF binds c-MET, c-MET activates ERK, and ERK drives GLS-1 transcription—an oncogenic kinase cascade wired directly into a metabolic enzyme.

The functional fallout was equally clear. In wound-healing assays, HGF-stimulated Detroit 562 monolayers closed scratches at 65.4 percent after twenty-four hours and 89.7 percent after forty-eight hours, compared with 40.3 and 70.5 percent in untreated controls—a marked boost in motility. ERK inhibition erased this pro-migratory effect, and HGF also increased phosphorylation of focal adhesion kinase, a surrogate marker of migratory activity, in a c-MET-dependent fashion. When the researchers silenced GLS-1 with siRNA, wound closure slowed significantly, demonstrating that the enzyme is not a passive bystander but a functional requirement for HGF-driven migration. Cell proliferation markers fell in parallel.

Mitochondrial physiology told the same story with quantitative precision. Using Seahorse extracellular flux analysis, which tracks the oxygen consumption rate (OCR) of living cells through sequential injection of oligomycin, the uncoupler BAM15, and rotenone/antimycin A, the team showed that HGF significantly raised both basal and maximal mitochondrial respiration in MET-amplified Detroit 562 cells. GLS-1 knockdown dropped basal and maximal OCR and abolished the HGF-induced respiratory boost. In MET wild-type FaDu cells, by contrast, HGF left respiration unchanged, and GLS-1 silencing reduced OCR independently of HGF—confirming that the metabolic response is a specific property of the MET-amplified state, not a general feature of head and neck cancer cells.

Critically, the laboratory findings survived contact with real patient data. Mining RNA-sequencing data from 522 primary tumors in the TCGA-HNSC cohort, the researchers found a significant positive Spearman correlation between MET and GLS1 expression (ρ = 0.432, p < 0.0001), a weaker but significant link between HGF and GLS1 (ρ = 0.165), and the strongest correlation of all between a composite MAPK/ERK transcriptional activity score—built from ten established ERK target genes including DUSP6, MYC, and CCND1—and GLS1 expression (ρ = 0.581, p < 0.0001). Stratifying patients by median MET expression, MET-high tumors showed significantly higher GLS1, along with elevated SLC1A5, the glutamine transporter, whereas the related gene GLS2 did not differ—underscoring the specificity of GLS1-dependent glutaminolysis downstream of c-MET.

The therapeutic implications are tantalizing, though the authors are careful to frame them appropriately. Single-agent c-MET inhibitors such as Foretinib and Tivantinib have shown limited efficacy in HNSCC, but the new data suggest that dual targeting of c-MET and GLS-1 could circumvent compensatory signaling, and next-generation glutaminase inhibitors such as CB-839 have already demonstrated activity in other malignancies. The bispecific EGFR/MET antibody Amivantamab, approved in non-small cell lung cancer and now showing promising early results in the OrigAMI-4 trial for HNSCC patients who progressed on checkpoint inhibitors and chemotherapy, adds further momentum. Because c-MET signaling has also been linked to PD-L1 induction and glutamine availability shapes antitumor immunity, combining MET blockade, GLS-1 inhibition, and immunotherapy is an openly debated possibility. Caveats remain: the study relied on 2D culture models centered on a single MET-amplified line, intracellular isotope-tracing flux measurements were not performed, and in vivo efficacy was not tested. Validation in 3D spheroids, patient-derived organoids, and animal models will be essential. Still, the work expands c-MET’s portfolio beyond proliferation and migration into metabolic sovereignty—and in doing so, hands oncologists a second target in a cancer that desperately needs more than one.

Subject of Research: HGF/c-MET signaling drives glutamine metabolism via MAPK/ERK-dependent GLS-1 induction in MET-amplified head and neck squamous cell carcinoma

Article Title: HGF/c-MET signaling induces glutamine metabolism in MET-amplified head and neck squamous cell carcinoma via MAPK/ERK-dependent induction of GLS-1

Article References: HGF/c-MET signaling induces glutamine metabolism in MET-amplified head and neck squamous cell carcinoma via MAPK/ERK-dependent induction of GLS-1. (n.d.). https://doi.org/10.1007/s12032-026-03409-0

Image Credits: AI Generated

DOI: 10.1007/s12032-026-03409-0

Keywords: HNSCC, c-MET, HGF, GLS-1, glutamine metabolism, MAPK/ERK, Foretinib, glutaminolysis, TCGA, cancer metabolism, mitochondrial respiration, Head and neck cancer