IISER Bhopal's Breakthrough in Breast Cancer Hypoxia Research

A team of scientists at the Indian Institute of Science Education and Research (IISER) Bhopal has made a significant discovery in understanding how breast cancer progresses under low-oxygen conditions. Led by Prof. Sanjeev Shukla from the Department of Biological Sciences, the research reveals that a lack of oxygen, known as hypoxia, triggers a cascade making breast cancer cells more invasive through a specific molecular pathway involving the protein PRMT5 (Protein Arginine Methyltransferase 5). This finding, published in the prestigious journal PLOS Biology, sheds light on why tumors in oxygen-poor environments become aggressive and spread more easily, offering potential new avenues for targeted therapies.

The study demonstrates that under hypoxia, CTCF (CCCTC-binding factor), a chromatin organizer, binds to the promoter region of the PRMT5 gene after demethylation of its DNA. This activation ramps up PRMT5 production, which then dimethylates histones H3R8 and H4R3 symmetrically. These modifications recruit DNMT3A (DNA Methyltransferase 3A), leading to DNA methylation at an intronic conserved region (ICR) in the TCF3 (Transcription Factor 3) gene. Methylated DNA attracts MeCP2 (Methyl-CpG-binding protein 2), causing RNA Polymerase II pausing and recruitment of PTBP1 (Polypyrimidine Tract Binding Protein 1), a splicing repressor. The result is alternative splicing favoring the exclusion of exon 18a and inclusion of exon 18b, producing the pro-invasive TCF3-18B isoform (also known as E47). This isoform suppresses E-cadherin, a key cell adhesion molecule, promoting epithelial-to-mesenchymal transition (EMT) and enhancing cell invasion.

What is Hypoxia and Why Does it Matter in Breast Cancer?

Hypoxia occurs when tumor growth outpaces the development of blood vessels, creating regions with insufficient oxygen supply. In breast cancer, this microenvironment is common, especially in solid tumors, and drives adaptation mechanisms that confer resistance to therapies and promote metastasis. Hypoxia-inducible factor 1-alpha (HIF1α) is the master regulator, stabilizing under low oxygen to activate genes for survival, angiogenesis, and metabolic shifts.

Step-by-step, hypoxia leads to:

• Stabilization of HIF1α, which dimerizes with HIF1β and translocates to the nucleus.
• Binding to hypoxia response elements (HREs) in target gene promoters.
• Epigenetic changes, including DNA demethylation via TET enzymes, enabling transcription factor access.
• Upregulation of genes like PRMT5, altering splicing and chromatin for invasiveness.

In India, where breast cancer is the leading cancer among women with nearly 240,000 new cases projected by 2026, understanding hypoxia is crucial. Late-stage diagnoses exacerbate the issue, as hypoxic tumors are harder to treat.

Unpacking the IISER Bhopal Mechanism: From CTCF to TCF3 Splicing

The elegance of the IISER Bhopal study lies in detailing the precise epigenetic and splicing choreography. Hypoxia first demethylates the PRMT5 promoter at CTCF binding sites, allowing CTCF to loop chromatin and pause RNA Pol II, boosting transcription. Elevated PRMT5 then targets the TCF3 ICR, depositing H3R8me2s and H4R3me2s marks. These recruit DNMT3A for hypermethylation, MeCP2 binding stabilizes the repressive complex, and PTBP1 shifts splicing toward the invasive TCF3-18B isoform.

Experiments confirmed this using CRISPR/Cas9 to delete the ICR, shRNA knockdowns of PRMT5/CTCF, and dCas9 fusions for targeted modulation. Matrigel invasion assays showed reduced cell penetration under PRMT5 inhibition, while TCF3-18B overexpression rescued phenotypes, proving causality.

In patient samples from Bansal Hospital, Bhopal, PRMT5 correlated with hypoxia marker CA9, validating clinical relevance. This axis explains why hypoxic breast tumors remodel extracellular matrix (ECM) for metastasis.

Prof. Sanjeev Shukla's Lab: Pioneering Epigenetics in Cancer

Prof. Shukla's Epigenetics and RNA Processing Lab at IISER Bhopal focuses on how epigenetic marks and alternative splicing drive cancer progression, particularly in triple-negative breast cancer (TNBC), which lacks targeted therapies. Previous works from the lab, like the HIF1α-ATF3-P4HA1 axis promoting collagen deposition via exon 9a inclusion, build this foundation. With funding from DBT and India Alliance, the lab exemplifies India's growing research prowess.

IISER Bhopal, established in 2008, fosters interdisciplinary training, attracting top talent. For aspiring researchers, opportunities abound in research jobs at such institutes, blending biology, bioinformatics, and chemistry.

Photo by Markus Winkler on Unsplash

Breast Cancer Landscape in India: Statistics and Challenges

India faces a breast cancer epidemic, with incidence rising 5-6% annually. Projections estimate over 232,000 cases in women by 2026, topping other cancers. Mortality remains high at ~100,000 yearly due to late detection, limited screening, and aggressive subtypes like TNBC prevalent in younger patients. Regional disparities show urban areas like Mumbai and Delhi with higher rates (25-30 per 100,000), but rural underreporting skews data.

• Age-standardized rate: 26.6 per 100,000 women.
• 5-year survival: 66.1% overall, lower in public hospitals.
• Hypoxia contributes to 50-60% poor prognosis cases.

Government initiatives like NPCDCS aim for early detection, but research like IISER's is vital for precision medicine.

Therapeutic Promise: Targeting PRMT5 and Hypoxia Pathways

The study tested GSK591, a PRMT5 inhibitor, which blocked histone marks, restored TCF3 splicing balance, reduced EMT markers (Vimentin up, E-cadherin down reversal), and curbed invasion. Ongoing clinical trials for PRMT5 inhibitors (e.g., GSK3326595 in solid tumors) show promise, with hypoxia-specific delivery enhancing efficacy.

Broader strategies include HIF1α inhibitors (PT2385), anti-angiogenics (bevacizumab), and nanoparticle oxygen delivery. Combining with immunotherapy could 'heat up' cold hypoxic tumors. In India, trials at AIIMS and TMC integrate these.

India's Role in Global Breast Cancer Research

Indian institutions contribute significantly, with IISERs, IITs, and ICMR leading. Collaborations with global labs (e.g., Shukla's DBT-Wellcome) accelerate translation. Patent filings from universities surged, though grants lag IITs.

Challenges: Funding (GERD 0.64% GDP), brain drain. Solutions: NEP 2020 boosts research, attracting postdoc positions.

Career Opportunities in Cancer Epigenetics Research

IISER Bhopal exemplifies training hubs for PhDs, postdocs in epigenetics. Skills: CRISPR, ChIP-seq, RNA-seq. Job market booms with biotech firms (Biocon, Syngene) hiring. Explore clinical research jobs or career advice for academia.

Photo by Artyom Korshunov on Unsplash

Future Outlook: From Bench to Bedside

This IISER study paves for PRMT5 biomarkers in hypoxic tumors, personalized therapies. Multi-omics integration, AI modeling predict responses. India's Anusandhan National Research Foundation (ANRF) funds such innovations.

For professionals, platforms like university jobs list faculty roles. Share insights on Rate My Professor. Stay updated via higher ed jobs and career advice.