Plant-Derived Molecule KGA-1002 Strikes GRP94 to Collapse Liver Cancer’s Protein Folding Machinery

A synthetic molecule built from the chemical skeleton of a common medicinal plant compound has emerged as one of the most mechanistically complete anti-liver-cancer candidates described in recent years. In a study published in the Journal of Advanced Research, a team led by Ji-Jun Chen at the Kunming Institute of Botany, Chinese Academy of Sciences, reports that the guaianolide dimer KGA-1002 kills hepatocellular carcinoma cells by binding a specific serine residue on the molecular chaperone GRP94, unleashing a cascade of unfolded protein stress that ultimately dismantles the tumor’s most important survival pathway. The work is the first to demonstrate that a selective GRP94 inhibitor can suppress liver cancer in living animals, and it arrives with an unusually detailed map of how the drug’s binding event propagates into cell death.

Hepatocellular carcinoma, the most common primary liver cancer, remains one of the world’s deadliest malignancies. It is the third leading cause of cancer-related death globally, and although viral hepatitis, alcohol consumption, aflatoxin exposure and poor diet all contribute to its development, the clinical picture is dominated by a single grim statistic: most patients are diagnosed at an advanced stage, when surgical options such as resection, transplantation or ablation are no longer viable. Approved drug therapies for advanced disease, including multikinase inhibitors such as sorafenib, lenvatinib and cabozantinib, and antibody combinations built around agents like bevacizumab and atezolizumab, have extended survival only modestly. The field’s persistent hunger for molecules with new structures and new mechanisms is what makes the KGA-1002 story notable.

The compound’s origin lies in the chemistry of Artemisia, the genus that gave the world artemisinin. Sesquiterpenoid dimers, molecules in which two sesquiterpene units are joined, have repeatedly shown stronger antitumor activity than their monomeric parents, but their scarcity in plants has historically blocked serious drug development. The Kunming group sidestepped that bottleneck through biomimetic synthesis: using a Diels-Alder reaction, they assembled KGA-1002 from dehydrocostus lactone, an abundant natural sesquiterpenoid, on a ten-gram scale. The resulting dimer inhibited the proliferation of three hepatocellular carcinoma cell lines with IC50 values of 5.9, 6.9 and 6.3 micromolar against HepG2, Huh7 and SK-Hep-1 cells respectively, outperforming sorafenib and beating the parent monomer dehydrocostus lactone by roughly five- to seven-fold.

Identifying what a small molecule actually touches inside a cell is the hardest part of natural product pharmacology, and the team attacked it with a battery of orthogonal techniques. A drug affinity responsive target stability assay, which exploits the fact that ligand-bound proteins resist enzymatic digestion, flagged a protein band that survived pronase treatment only in the presence of KGA-1002. Mass spectrometry of that band yielded 49 candidate proteins, which transcriptomic profiling and bioinformatics narrowed to six. The decisive experiment was genetic: when the researchers silenced each candidate in liver cancer cells, only knockdown of GRP94, the endoplasmic reticulum-resident member of the heat shock protein 90 family, blunted the drug’s antiproliferative and anti-migratory effects. Surface plasmon resonance then measured direct binding, with a dissociation constant of 454 nanomolar, and a cellular thermal shift assay confirmed that KGA-1002 stabilizes GRP94 inside cells.

The structural detail goes further than most target-identification studies dare. KGA-1002 carries an alpha, beta-unsaturated carbonyl motif, a well-known covalent warhead, and molecular dynamics simulations showed that this group is essential for stabilizing the GRP94-ligand complex. Mass spectrometric sequencing of the treated protein revealed a peptide whose mass had increased by exactly the molecular weight of the drug, and secondary fragmentation localized the covalent bond to serine 106, a hydroxyl-bearing residue ideally positioned for nucleophilic attack on the unsaturated carbonyl. When the team mutated serine 106 to alanine, binding affinity collapsed from 522 nanomolar to 461 micromolar, a nearly thousand-fold loss. Critically, KGA-1002 did not stabilize the cytosolic family members HSP90alpha or HSP90beta, whose indiscriminate inhibition has doomed pan-HSP90 drugs in clinical trials. That isoform selectivity, aided by an additional contact with GRP94-specific asparagine 276, is arguably the compound’s most clinically relevant property.

With the target pinned down, the downstream biology fell into place. GRP94’s day job is folding, assembling and trafficking client proteins inside the endoplasmic reticulum, and its inhibition floods the ER lumen with misfolded polypeptides. Transcriptomic analysis of treated cells showed enrichment of ER-related pathways, upregulation of stress genes such as ERN1, ATF4 and DDIT3, and downregulation of ER trafficking genes. The canonical unfolded protein response sensors PERK and IRE1, normally held inactive by the chaperone BiP, were activated, driving expression and nuclear translocation of the death-promoting transcription factors XBP1 and CHOP. Because GRP94 also buffers calcium in the ER, the drug produced a dose-dependent rise in intracellular calcium, climbing to nearly 98 percent calcium-positive cells at 7.5 micromolar in both SK-Hep-1 and Huh7 lines. The unfolded protein response, in other words, was not a side effect but the engine of tumor killing.

The most novel mechanistic finding concerns AKT, the kinase at the heart of the PI3K survival pathway. KGA-1002 lowered AKT protein levels without touching its mRNA, and cycloheximide chase experiments showed the drug accelerating AKT degradation; proteasome and lysosome inhibitors each partially rescued the protein, implicating both disposal routes. The explanation proved to be a chaperone-client relationship: GRP94 physically holds AKT, and pulldown assays demonstrated that KGA-1002 disrupts that interaction, both in cell lysates and with purified proteins. Destabilized AKT could no longer phosphorylate SKP2, the F-box substrate-recognition protein of an E3 ubiquitin ligase that normally tags the cell cycle brake P21 for destruction. Deprived of AKT’s stabilizing phosphorylation, SKP2 itself was degraded through the proteasome, P21 accumulated in the nucleus, and the cells arrested in G0/G1 and died. Clinical databases reinforced the story: both GRP94 and SKP2 are overexpressed in hepatocellular carcinoma tissues and correlate with poor survival.

The death program did not stop at apoptosis. With AKT signaling crippled, the antioxidant defenses of the cell, maintained through the AKT-mTOR axis, Nrf2 and GSK-3beta, eroded, and reactive oxygen species accumulated. Mitochondrial membrane potential collapsed, lipid peroxidation measured as malondialdehyde rose, the ferroptosis gatekeeper GPX4 fell, and labile iron climbed, all hallmarks of ferroptosis, the iron-dependent form of regulated cell death. The ROS scavenger N-acetylcysteine and the ferroptosis inhibitor liproxstatin-1 each blunted these effects, confirming causality. KGA-1002 thus kills liver cancer cells along two converging routes, ER stress-driven apoptosis and AKT-dependent ferroptosis, both traceable to a single upstream lesion at GRP94.

In vivo, the compound held up. In nude mice bearing subcutaneous SK-Hep-1 tumors, intraperitoneal KGA-1002 at 15, 30 and 60 milligrams per kilogram over 60 days shrank tumors by 44.1, 52.1 and 53.5 percent, with the top dose matching sorafenib; direct intratumoral injection performed even better, reaching 61.6 percent inhibition. Tumors from treated animals showed reduced Ki67 staining and elevated phosphorylated IRE1 and PERK, confirming that the ER stress mechanism operates in living tissue. The decisive target-validation experiment came from xenografts grown from GRP94-knockdown cells: with the target partially removed, the drug’s antitumor effect and its suppression of Ki67 were significantly weakened, establishing that KGA-1002’s efficacy is GRP94-dependent. Safety readings were reassuring, with no weight loss, behavioral changes, liver or kidney function abnormalities, and no histopathological organ damage even at 150 milligrams per kilogram in a separate subacute study.

The study’s authors are careful about scope, and so should readers be. The work rests on cell lines and subcutaneous mouse models, not orthotopic liver tumors or patients, and a selectivity index of roughly 1.5 to 1.7 over normal hepatocytes, while adequate, leaves room for optimization. Yet the conceptual payoff is substantial: GRP94 has been implicated in breast cancer metastasis and multiple myeloma, and the authors note it is also overexpressed in colon, esophageal and bladder cancers, so a validated, covalent, isoform-selective inhibitor scaffold is a tool the wider oncology community can build on. By showing exactly where the molecule docks, which residue it attacks, and how that single molecular event cascades through protein folding, calcium handling, AKT stability, SKP2 degradation and ferroptosis, the Kunming team has delivered something rarer than another cytotoxic natural product: a mechanistically coherent proof that GRP94 is a druggable vulnerability in liver cancer, and a lead compound engineered to exploit it.

Subject of Research: A selective GRP94 inhibitor derived from a guaianolide sesquiterpenoid dimer as a therapeutic agent against hepatocellular carcinoma

Article Title: Guaianolide dimer KGA-1002 targets GRP94 and triggers unfolded protein response-associated degradation of SKP2/AKT axis as a novel antihepatoma agent

Article References: Li, Q.-H., Li, T.-Z., Wang, Y.-C., Huang, X.-Y., Ma, W.-J., Li, F.-J., Huang, F.-D., Hu, M.-M., & Chen, J.-J. (2026). Guaianolide dimer KGA-1002 targets GRP94 and triggers unfolded protein response-associated degradation of SKP2/AKT axis as a novel antihepatoma agent. Journal of Advanced Research, 88, 1077-1093. https://doi.org/10.1016/j.jare.2026.01.010

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.01.010

Keywords: hepatocellular carcinoma, GRP94, KGA-1002, guaianolide dimer, unfolded protein response, AKT, SKP2, P21, ferroptosis, endoplasmic reticulum stress, natural products, drug discovery