CULTURE CONFUSION: HeLa cells (pictured here) are a common contaminant of cell lines.NATIONAL INSTITUTES OF HEALTH/WIKIPEDIA
In the early days of cell culture, researchers often struggled to get their cell lines to survive for long periods of time. At first, some investigators blamed inappropriate culture conditions and kept tweaking the recipe, hoping to get it right. HeLa cells, first cultured in 1951 from cervical cancer tissue, were cloned in 1955 and became the first human cell line capable of permanent growth in culture. Thereafter, dozens of other permanent human cell lines were reported in the literature, suggesting that they were relatively easy to establish. However, in the 1960s, Leonard Hayflick and his colleagues published a landmark series of papers explaining the initial difficulties in getting cells to grow indefinitely: normal human fibroblasts grown in culture divide a finite number of times.
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