What Is HeLa Cell Contamination and Why Does It Matter?

Cell line contamination, where one cell culture is unintentionally overgrown by another, is a persistent issue in biomedical research. The most notorious example involves HeLa cells, a human cell line used extensively worldwide. Derived from a patient in the 1950s, these cells have unique properties that make them both an invaluable research tool and an aggressive contaminant. Their widespread, often undetected, presence in other cell cultures has created challenges, casting doubt on scientific findings and highlighting the need for rigorous lab practices.

The Origin and Unique Properties of HeLa Cells

HeLa cells originated from Henrietta Lacks, an African American woman diagnosed with cervical cancer in 1951. During her treatment at Johns Hopkins Hospital, a sample of her cancerous tissue was taken without her consent. A cell biologist named George Otto Gey discovered these cells could grow indefinitely in a lab, making them the first “immortal” human cell line. This meant the cells did not die off after a set number of divisions, a process called cellular senescence.

This immortality, combined with a rapid growth rate, made HeLa cells a powerful tool for medical research. This gave scientists a consistent, renewable source of human cells to study diseases, test drugs, and develop vaccines. The cells proved robust and adaptable, capable of thriving in various culture conditions.

These same properties, however, also make HeLa cells a formidable contaminant. Their aggressive growth allows them to easily outcompete and take over other, slower-growing cell cultures. Because of their hardiness, they can survive where other cells might perish, leading to a complete replacement of the original culture without researchers noticing.

Pathways of HeLa Cell Contamination in Laboratories

HeLa cells spread through labs due to unrecognized cross-contamination. For decades, a lack of awareness and effective detection tools meant the problem was not fully understood. This allowed HeLa to infiltrate other cell lines, often without any visible indication of a takeover.

One common pathway is through shared media or other reagents. If a bottle of media is used for a HeLa culture and then for another cell line without changing pipette tips, a few stray cells can be transferred. Given their rapid growth, these cells can quickly dominate the new culture.

Aerosol generation is another common contamination route. Pipetting, opening flasks, or splashing media can create airborne droplets containing cells that travel across a lab and settle into other cultures. Improper aseptic techniques amplify this risk, while mislabeling flasks or vials can also lead to a mix-up of cell lines.

Historically, labs freely exchanged cell lines, creating a domino effect. If a lab sent a contaminated culture to another group, they would use and further distribute the tainted line, spreading misidentified cells. For instance, cell lines thought to be from human amnion (WISH cells) or endometrial tissue (HES cells) were later discovered to be HeLa cells.

Impact of HeLa Contamination on Scientific Integrity

Using HeLa-contaminated cell lines has severe consequences, undermining scientific integrity. When scientists believe they are studying one type of cell, such as lung cancer, but are actually working with cervical cancer cells (HeLa), their conclusions become invalid. This leads to publishing erroneous data and misunderstanding the biology being investigated.

The issue wastes significant resources, as years of work and millions in funding can be spent on research based on a false premise. Flawed studies are often cited, leading future research down incorrect paths. This can hinder progress in understanding diseases and developing effective therapies.

The problem also damages scientific credibility by eroding reproducibility, a core scientific principle. When others cannot replicate findings because the original work used the wrong cells, it creates confusion and doubt. In many cases, this has led to the retraction of published papers, damaging the reputations of the researchers and institutions involved.

Identifying and Mitigating HeLa Contamination

Methods were developed to authenticate cell lines in response to the contamination problem. The primary technique is Short Tandem Repeat (STR) profiling, which analyzes specific DNA regions to create a unique genetic fingerprint for each cell line. By comparing a culture’s STR profile to a reference database, researchers can confirm its identity or detect contamination.

To prevent contamination, laboratories must adhere to strict best practices in cell culture. This includes practicing good aseptic technique, such as sterilizing equipment and work surfaces, and working with only one cell line at a time. Using separate bottles of media for each distinct cell line is another preventative measure.

Regular authentication and careful sourcing are also necessary. Other key strategies include:

• Testing cells upon receipt from a supplier, before freezing, and at regular intervals during use.
• Sourcing cells from reputable cell banks that perform routine authentication.
• Maintaining meticulous records of all cell cultures.
• Quarantining all new, unverified cell lines until their identity is confirmed.