Although integrins are known to mediate invasion and metastasis, recent studies reveal new
ways in which they contribute to squamous-cell carcinoma. Integrin mutation or upregulation
can expand the tumour stem-cell compartment by inhibiting differentiation or apoptosis.
Integrins that are expressed by differentiated cells can stimulate or inhibit the proliferation of
neighbouring tumour stem cells. These findings provide a mechanistic basis for the well-
established links between altered integrin expression and tumour prognosis.