Isr Med Assoc J
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Klotho is a transmembrane protein that can be shed and can act as a circulating hormone in three forms: soluble klotho (KL1 + KL2), KL1, and KL2. Klotho was discovered as a gene implicated in aging through inhibition of the IGF-I pathway. Our laboratory discovered the role of klotho as a tumor suppressor in breast cancer and other malignancies. Furthermore, we showed that the KL1 domain mediates this activity. Altered cancer cell metabolism is a hallmark of cancer and our lab demonstrated various effects of klotho on breast cancer cell metabolism. Thus, klotho inhibited glycolysis and activated adenosine monophosphate activating kinase (AMPK), an energy sensor pathway. Moreover, inhibition of AMPK reduced the tumor suppressor activity of klotho. ⋯ Our data indicate KL1 as a regulator of metabolic activity in breast cancer and suggest that metabolic alterations underlie KL1 tumor suppressor activities. Furthermore, as KL1 and klotho share a similar effect on cell metabolism, our results further support the central role KL1 domain plays in klotho's tumor suppressor activity.