(PA-303) STAT3 Inhibitors Inducing DNA Damage in Multiple Myeloma Cells and Enhancing the Anti-tumor Effects of NK Cells

To investigate the anti-tumour cellular effects and mechanisms of DNA damage-induced activation of NK cells by STAT3 inhibitors in MM cells.

Methods:

Using data of MMRF-CoMMpass studies to identify the prognostic value of STAT3 and PARP1. Using CCK-8 to explore the Half-maximal inhibitory concentration (IC50) of STAT3 inhibitor C188-9 in MM cell lines U266 and RPMI-8266. Using flow cytometry (FCM) to evaluated the apoptosis and the expression of MICA/B in MM cells. Using western-blot to measure the level of STAT3, H2AX and ATM. We co-cultured MM cells with NK cells and measure the activation of NK cells and the level of apoptosis of MM cells by using FCM.

Results:

By using the data of MMRF-CoMMpass, we found that patients with higher expression was associated worse prognosis. The IC50 of C188-9 in U266 was 23.07μM while in RPMI-8226 was 44.16μM. The C188-9 can significantly induce the level of apoptosis and expression MICA/B of MM cells. Western blot should that inhibition of STAT3 could elevated the levels of H2AX and ATM. For PARP1 inhibitor BYK204165, it had no effect on the apoptosis and the level of MICA/B. However, when it combined with C188-9, it could induce higher levels of apoptosis and expression of MICA/B of MM cells. Western blot also verified higher level of H2AX and ATM when C188-9 combined with BYK204165.  With the cotreatment of C188-9 and BYK204165, we found upregulation of NKG2D, perforin and granzyme B and heightened cytotoxicity in NK cells in Coculture of NK cells with the MM cells.  

Conclusions:

We found STAT3 inhibitor induces apoptosis and DNA damage in MM cells and STAT3 inhibitor combined with PARP1 inhibitor induced apoptosis and DNA damage in MM cells and mediated the high expression of MICA/B in MM cells. What’s more, STAT3 inhibitor combined with PARP1 inhibitor induces DNA damage in MM cells, mediates high expression of MICA/B in MM cells, and activates the anti-tumour effect of NK cells.