Tumour heterogeneity

Tumour heterogeneity describes the observation that different tumour cells can show distinct morphological and phenotypic profiles, including cellular morphology, gene expression, metabolism, motility, proliferation, and metastatic potential.^[1] This phenomenon occurs both between tumours (inter-tumour heterogeneity) and within tumours (intra-tumour heterogeneity). A minimal level of intra-tumour heterogeneity is a simple consequence of the imperfection of DNA replication: whenever a cell (normal or cancerous) divides, a few mutations are acquired^[2]—leading to a diverse population of cancer cells.^[3] The heterogeneity of cancer cells introduces significant challenges in designing effective treatment strategies. However, research into understanding and characterizing heterogeneity can allow for a better understanding of the causes and progression of disease. In turn, this has the potential to guide the creation of more refined treatment strategies that incorporate knowledge of heterogeneity to yield higher efficacy.^[4]

Tumour heterogeneity has been observed in leukemias,^[5] breast,^[6] prostate,^[7][8][9] colon,^[10][11][12] brain,^[13] esophagus,^[14] head and neck,^[15] bladder^[16] and gynecological carcinomas,^[17] liposarcoma,^[18] and multiple myeloma.^[19]