Unveiling the Mechanisms of Chemotherapy Resistance in Colorectal Cancer

Singapore's research powerhouse, the Agency for Science, Technology and Research (A*STAR), has delivered a pivotal breakthrough in understanding why some colorectal cancer (CRC) tumors recur and spread despite aggressive chemotherapy. Led by Dr. Ramanuj DasGupta at the A*STAR Genome Institute of Singapore (GIS), in collaboration with the National Cancer Centre Singapore (NCCS), Singapore General Hospital (SGH), and KU Leuven in Belgium, the study pinpoints the gene SERPINE1 as a master regulator driving both drug resistance and metastatic potential post-treatment.

Published in Nature Cell Death & Disease on July 16, 2025, the research employs clinically relevant dosing models of oxaliplatin—a frontline chemotherapy drug for CRC—to mimic real-world treatment scenarios. Traditional lab models often use unrealistically high doses, but this approach reveals how surviving cancer cells undergo a 'survival shift,' reprogramming their metabolism and gene expression to evade death and prepare for invasion.

This discovery is timely for Singapore, where CRC ranks as the second most common cancer. Between 2019 and 2023, the Singapore Cancer Registry recorded 12,950 new cases, highlighting the urgent need for strategies to combat recurrence, which affects up to 50% of patients and drives most CRC deaths.

Colorectal Cancer Burden in Singapore: Rising Incidence and Early-Onset Trends

Colorectal cancer, originating in the colon or rectum, arises from uncontrolled growth of cells lining the large intestine. In Singapore, age-standardized incidence rates (ASR) for CRC peaked around 1992 before stabilizing, yet the disease remains a top killer. The five-year survival for localized CRC exceeds 90%, but drops sharply to 73% for regional spread and lower for metastatic cases.

Alarmingly, early-onset CRC (under age 50) is rising, with studies showing a 3% annual increase in the 50-64 age group historically, now extending younger. Factors include Westernized diets high in red meat and low fiber, obesity, sedentary lifestyles, and genetic predispositions like Lynch syndrome. Singapore's multi-ethnic population sees varying risks: higher among Indians and Malays compared to Chinese, per registry data.

The National CRC Screening Programme, offering free fecal immunochemical tests (FIT) for ages 50-75, has boosted early detection, but participation hovers around 40%, underscoring education gaps. With projections estimating rising cases amid an aging population, innovations like A*STAR's work are crucial.

How Chemotherapy Triggers a Deadly Transformation

Oxaliplatin, a platinum-based drug, damages DNA in rapidly dividing CRC cells, halting replication. Standard neoadjuvant or adjuvant regimens shrink tumors pre- or post-surgery. However, residual cells adapt via multiple mechanisms: DNA repair upregulation, efflux pumps expelling the drug, and metabolic rewiring.

In the A*STAR study, researchers exposed CRC cell lines (HCT116, SW480) to escalating clinically relevant doses over 10 cycles. Survivors—termed oxaliplatin-resistant (OxR) cells—exhibited slower proliferation but heightened invasion and migration. In mouse xenografts, these cells formed fewer primary tumors yet more lung metastases, mirroring therapy-induced dissemination in patients.

• Low-dose OxR: Mild resistance, subtle metastatic shift.
• Mid/High-dose OxR: Pronounced SERPINE1 upregulation, aggressive spread.

Transcriptomics revealed enriched coagulation and epithelial-mesenchymal transition (EMT) pathways, hallmarks of plasticity enabling survival and motility.

SERPINE1: The Central Culprit in Resistance and Metastasis

SERPINE1, encoding plasminogen activator inhibitor-1 (PAI-1), emerged as the top upregulated gene in OxR cells. PAI-1 regulates fibrinolysis but in cancer promotes ECM remodeling, angiogenesis, and immune evasion. High SERPINE1 correlates with poor CRC prognosis across datasets like TCGA.

Step-by-step mechanism:

1. Oxaliplatin selects OxR cells with downregulated cholesterol biosynthesis (e.g., HMGCR, FDPS).
2. Reduced cholesterol disrupts lipid rafts, impairing TGF-β receptor (TGFBR) internalization.
3. Sustained TGF-β signaling boosts SERPINE1 transcription.
4. SERPINE1 drives EMT, invasion, and oxaliplatin efflux, linking resistance to metastasis.

Single-cell RNA-seq confirmed SERPINE1 in drug-tolerant persister clusters. Knocking down SERPINE1 via shRNA or inhibitors (tiplaxtinin) restored oxaliplatin sensitivity and curbed lung mets in vivo.

Photo by j . on Unsplash

The RESIST-M Gene Signature: A Prognostic Powerhouse

From OxR transcriptomes, researchers derived RESIST-M—a nine-gene signature (SERPINE1-high RESIST-M1; cholesterol-low RESIST-M2). Validated in TCGA (n=377), PETACC-3 (n=604), and Singapore cohorts (n=162), high RESIST-M scores predict relapse-free survival (RFS) and overall survival (OS), outperforming others.

Enriched in CMS4 (mesenchymal/stromal-rich, aggressive subtype), RESIST-M flags high-risk patients for intensified surveillance or trials. Prof. Iain Tan notes its potential for personalized decisions, like statin combos.

Therapeutic Vulnerabilities: Statins and Beyond

FDA-approved screens identified cholesterol inhibitors (simvastatin) and ROS inducers (elesclomol) as synthetically lethal with OxR cells. Simvastatin reversed TGF-β hyperactivation, downregulated SERPINE1, and synergized with oxaliplatin in xenografts, shrinking tumors 50-70% more.

Read the full study for protocols. Ongoing trials may test these in CMS4 patients, building on Singapore's precision oncology push like SYMPHONY.

• Benefits: Repurposed drugs, low cost, accessible.
• Risks: Statin side effects (myopathy); needs monitoring.
• Comparisons: Superior to monotherapy in models.

Singapore's Research Ecosystem Tackling CRC

A*STAR GIS exemplifies Singapore's biomedical hub, partnering with NCCS for translational impact. Related A*STAR works include CAN-Scan (ML for drug response) and Colo-SCRIPT (CRC genomics). Government invests S$50M in precision oncology, fostering jobs in higher-ed research roles.

Stakeholders: MOH pushes screening; patients advocate awareness. Multi-perspective: Oncologists hail biomarkers; researchers eye trials; policymakers fund ecosystem.

Implications for Prevention, Screening, and Patient Care

While targeted therapies evolve, prevention reigns: High-fiber diets, exercise, no smoking. Singapore's FIT screening detects 90% early lesions; uptake rising but target 70% by 2030.

RESIST-M could guide post-chemo monitoring via liquid biopsy. For high-risk (e.g., family history), start screening at 45. Actionable: Discuss statins with oncologists if CMS4.Explore oncology careers.

Photo by Sraboni Basu on Unsplash

Future Outlook: From Bench to Bedside in Precision Oncology

Next: Refine RESIST-M for clinical assays, Phase II trials of statin-oxaliplatin, SERPINE1 drugs. Broader: Integrate with AI like CAN-Scan for holistic prediction. Singapore leads Asia in CRC research output.

Optimistic: 5-year survival could hit 75% with biomarkers. Researchers like Dr. DasGupta envision relapse prevention, transforming CRC from lethal to manageable.

Explore research jobs, rate professors, or career advice in oncology. For Singapore opportunities, visit AcademicJobs.sg.