PTEN-L induce PTEN-null tumor cells dormancy but lung outgrowth.

PTEN is one of the most frequently mutated tumor suppressor genes, its loss has been reported in multiple tumor types and is associated with a poor outcome. PTEN-L, as a secreted isoform of PTEN, with the ability to enter cells and inhibit tumor cell growth via inhibiting AKT mediated cell proliferation. However, the distinct effect of PTEN-L on PTEN-expression or PTEN-loss tumor cells is not known yet. Here, we identified PTEN-L treatment facilitate E0771-PTEN-null tumor cells, but not PTEN-wide-type tumor cells lung outgrowth. RNA-seq and Western blot analysis suggest PTEN-L stimulation induced PTEN-null tumor cells dormancy, namely, upregulation of dormancy markers p16 and p27, cell cycle arrest, reduced cell proliferation and chemotherapy drugs resistance. Further study suggested PTEN-L mediated p38 signaling activation play the major role for PTEN-null tumor cell dormancy. The p38 inhibitor, SB202190 significantly reversed the PTEN-L induced PTEN-null tumor cells dormancy and outgrowth in lungs. Further investigation indicated the dormant PTEN-null tumor cells could escape from immunosurveillance and thus outgrowth in lungs, as PTEN-L did not promote PTEN-null tumor cells outgrowth in lung of SCID mice. Therefore, we propose that PTEN-L protects PTEN-null tumor cells from immune attack during lung metastasis via activating dormancy related pathways. This study identified PTEN-L as an activator of PTEN-loss tumor cells dormancy, which enables the efficient seeding and outgrowth of tumor cells in metastatic niches. Overall, we highlight PTEN expression status decides the outcome of PTEN-L mediated anti-tumor therapy.