1q21.3

TORC-2,TORC2

Peutz-Jeghers syndrome (PJS) is an autosomal-dominant genetic disorder that is characterised by an increased risk of developing malignant tumours. Most of the identified mutations in the LKB1 gene are localised to the catalytic kinase domain so that it is thought that PJS results from loss of LKB1 kinase activity. The silencing of LKB1, leads to the decreased activity of AMPK and SIK and leads to the increased nuclear translocation and activity of CRTC2.

Gastrointestinal polyps and cancers including esophagus, stomach, small intestine, colon, pancreas, lung, testes, breast, uterus, ovary and cervix.

Oestrogen-receptor (ER) positive breast cancer

The increased prevalence of oestrogen-dependent, postmenopausal breast cancers is correlated with elevated local levels of oestrogens as a result of an increase in cytochrome P450 aromatase expression within the adipose stromal (hAS) cells surrounding the breast tumour - aromatase is the enzyme responsible for the conversion of androgens to oestrogens. This is governed by promoter switching from the distal promoter I.4 to the proximal promoter PII on the CYP19A1 gene, that encodes aromatase, in response to factors derived from the tumour such as prostaglandin E2 (PGE2). Interestingly, the LKB1/ AMPK pathway has been shown to inhibit aromatase expression via the cytoplasmic sequestration of CRTC2. However, PGE2 inhibits LKB1/AMPK signaling, leading to the nuclear translocation of CRTC2 and its enhanced binding and activation of aromatase promoter PII in hAS cells. Furthermore, the adipokine leptin, produced at higher levels in obesity, has been shown to cause an increase in CRTC2 nuclear translocation and consequently, in aromatase expression.