Breast cancer cells in a petri dish with oxygen molecules in the background.

Breast Cancer Cell Lines: The Oxygen Connection You Need to Know

Avery Sinclair in Science & Nature August 2025 • 4 min read.

"Discover how growing breast cancer cells in more natural oxygen levels (5%) can change how we understand and treat this disease."

For years, most breast cancer cells studied in labs have been grown in air that's about 21% oxygen. This is much higher than the oxygen levels in our bodies, which usually average around 5%. This difference in oxygen can actually change how the cells behave, potentially skewing research results.

A new study is diving into this issue by growing breast cancer cells in a more realistic, low-oxygen (5%) setting. The goal is to see if these cells act differently and whether this could help us develop better ways to treat breast cancer.

These findings shed light on the importance of replicating true body conditions when studying cancer cells.

The 5% Oxygen Advantage: What the Study Revealed

Breast cancer cells in a petri dish with oxygen molecules in the background.

Scientists created four new breast cancer cell lines and grew them in 5% oxygen. They then compared these cells to standard cell lines grown in 21% oxygen, looking at various factors like:

Cell appearance and DNA content, Mutation patterns, Hormone receptor status (whether the cells respond to hormones like estrogen), Activity of important cell pathways and Sensitivity to different cancer drugs

Three of the new cell lines (NZBR1, NZBR2, NZBR4) were triple-negative, meaning they didn't have estrogen receptors (ER-), progesterone receptors (PR-), or HER2. NZBR1 also had high levels of EGFR, a protein that can fuel cancer growth.
One cell line (NZBR3) was HER2-positive and ER-positive, also over-expressing EGFR.
Cells grown in 5% oxygen had more of a protein called CA9, which is linked to low-oxygen conditions and less ROS.
NZBR1 had less activity in the AKT pathway, while NZBR2 and NZBR4 had less activity in the p70S6K and rpS6 pathways.

The study also found some differences in gene mutations compared to standard cell lines. For example, mutations in TP53, a key tumor suppressor gene, were absent in the new cell lines. Also, mutations in genes like EVI2B, LRP1B, and PMS2, not typically seen in other breast cancer lines, were present.

What This Means for Breast Cancer Research

While these new cell lines share many similarities with existing ones, the low-oxygen environment did seem to influence certain cell behaviors, potentially impacting research results. By studying cancer cells in conditions that more closely mimic the body, researchers may gain a more accurate understanding of the disease and develop more effective therapies. Further studies may reveal the importance of low-oxygen conditions on the effectiveness of drugs in treating cells.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.3389/fonc.2018.00425, Alternate LINK

Title: Derivation Of Breast Cancer Cell Lines Under Physiological (5%) Oxygen Concentrations

Subject: Cancer Research

Journal: Frontiers in Oncology

Publisher: Frontiers Media SA

Authors: Euphemia Y. Leung, Marjan E. Askarian-Amiri, Dean C. Singleton, Carole Ferraro-Peyret, Wayne R. Joseph, Graeme J. Finlay, Reuben J. Broom, Purvi M. Kakadia, Stefan K. Bohlander, Elaine Marshall, Bruce C. Baguley

Published: 2018-10-12

Everything You Need To Know

Why is it important to study breast cancer cell lines in 5% oxygen rather than the standard 21%?

Most breast cancer research uses cells grown in 21% oxygen, which is much higher than the 5% typically found in the human body. Growing cells at 21% oxygen, can alter cellular behavior. The study described focuses on the differences between cell lines grown in 21% versus 5% oxygen levels, exploring the implications for understanding and treating breast cancer.

How did scientists compare breast cancer cell lines grown in 5% oxygen to those grown in standard conditions?

Scientists created four new breast cancer cell lines (NZBR1, NZBR2, NZBR3, and NZBR4) and cultured them in a 5% oxygen environment. They analyzed characteristics such as cell appearance, DNA content, mutation patterns, hormone receptor status (ER, PR, and HER2), and the activity of cell pathways. Comparing these new cell lines to standard cell lines grown at 21% oxygen reveals how a low-oxygen environment influences cancer cell behavior.

What key differences were observed in the breast cancer cell lines grown in 5% oxygen compared to those grown in standard conditions?

The study identified key differences in the breast cancer cell lines (NZBR1, NZBR2, NZBR3 and NZBR4) grown in 5% oxygen. Three of the new cell lines (NZBR1, NZBR2, NZBR4) were triple-negative, and NZBR1 also had high levels of EGFR. NZBR3 was HER2-positive and ER-positive, also over-expressing EGFR. Cells grown in 5% oxygen had more of a protein called CA9, and NZBR1 had less activity in the AKT pathway, while NZBR2 and NZBR4 had less activity in the p70S6K and rpS6 pathways. Additionally, some gene mutations, like those in TP53, were absent, while others, like those in EVI2B, LRP1B, and PMS2, were present.

What are the potential implications of growing breast cancer cell lines in 5% oxygen for developing new treatments?

Growing breast cancer cell lines (NZBR1, NZBR2, NZBR3 and NZBR4) in 5% oxygen, influenced specific cell behaviors. By studying cells in conditions that more closely mimic the body’s natural environment, researchers may achieve a more accurate understanding of the disease. This approach could lead to the development of more effective therapies that target the unique characteristics of cancer cells in their natural, low-oxygen environment, potentially improving treatment outcomes. More studies will need to be done to measure the effectiveness of drugs on cells grown in low-oxygen conditions.

Why is hormone receptor status (ER, PR, HER2) important in the context of breast cancer cell lines, like NZBR1, NZBR2, NZBR3 and NZBR4?

Hormone receptor status, specifically the presence or absence of estrogen receptors (ER), progesterone receptors (PR), and HER2, is a critical factor in classifying breast cancer. Triple-negative breast cancers (like NZBR1, NZBR2, NZBR4) lack these receptors, making them less responsive to hormone therapies. HER2-positive cancers (like NZBR3) have an overabundance of the HER2 protein, which can be targeted with specific therapies. Understanding hormone receptor status guides treatment decisions and is essential for personalized cancer care.