Cell line cross-contamination in the laboratory is often the result of failing to adopt good cell culture practices. Common causes may include: 

• Mislabeling flasks 
• Misreading flask labels
• Accidentally inoculating one cell line with another cell line
• Storing multiple cell lines together in a safety cabinet 
• Using one reservoir of medium for multiple cell lines simultaneously
• Accidentally transferring cells to stock bottle
• Thawing a wrong frozen stock
• Using the same tools when working with different cell lines
• Using cell samples that are not tested thoroughly 

Adopting good cell culture practices combined with regular quality control is key to eliminating cell line cross contamination which compromises research results leading to unusable therapeutic products.