Tracy Lee, Sandra Babich, Kasia Konopacki, John Chen, Jenna Moccia, and Bert Wognum
STEMCELL Technologies Inc., Vancouver, BC, Canada
Over the past decade, the number of biotherapeutic drugs produced in Chinese hamster ovary (CHO) cells has increased dramatically. To achieve consistently high expression of a protein product, monoclonal cultures of transfected CHO cells are generated by single-cell cloning after plating cells at very low densities. Efﬁcient expansion of single CHO cells typically requires the use of medium containing fetal bovine serum (FBS) or alternatively, use of conditioned medium or co-culture with feeder cells. However, these systems are not deﬁned, and batch variation and risk of contamination from adventitious agents make the use of FBS undesirable. Chemically-deﬁned, protein-free media, which are available from many suppliers, can effectively support CHO cell cultures for many passages when cells are plated at high densities. However, cloning efﬁciency in these media is very low if the cells are plated at the very low densities necessary for limiting dilution cloning. To address these issues, we have developed a deﬁned, animal component-free (ACF) culture supplement that contains only recombinant proteins and synthetic components. The ClonaCell™-CHO ACF Supplement signiﬁcantly increases the cloning efﬁciency of CHO cells plated at low density in protein-free media from various commercial suppliers.
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