KPT-9274, an Inhibitor of PAK4 and NAMPT, Leads to Downregulation of mTORC2 in Triple Negative Breast Cancer Cells

Abstract

Triple negative breast cancer (TNBC) is difficult to treat due to lack of druggable targets. We have found that treatment with the small molecule inhibitor KPT-9274 inhibits growth of TNBC cells and eventually leads to cell death. KPT-9274 is a dual specific inhibitor of PAK4 and Nicotinamide Phosphoribosyltransferase (NAMPT). The PAK4 protein kinase is often highly expressed in TNBC cells and has important roles in cell growth, survival, and migration. Previously we have found that inhibition of PAK4 leads to growth inhibition of TNBC cells both in vitro and in vivo. Likewise, NAMPT has been shown to be dysregulated in cancer due to its role in cell metabolism. In order to understand better how treating cells with KPT-9274 abrogates TNBC cell growth, we carried out an RNA sequencing of TNBC cells treated with KPT-9274. As a result, we identified Rictor as an important target that is inhibited in the KPT-9274 treated cells. Conversely, we found that Rictor is predicted to be activated when PAK4 is overexpressed in cells, which suggests a role for PAK4 in the regulation of Rictor. Rictor is a component of mTORC2, one of the complexes formed by the serine/threonine kinase mTOR. mTOR is important for the control of cell growth and metabolism. Our results suggest a new mechanism by which the KPT-9274 compound may block the growth of breast cancer cells, which is via inhibition of mTORC2 signaling. Consistent with this, sequencing analysis of PAK4 overexpressing cells indicates that PAK4 has a role in activation of the mTOR pathway.

The Role of p21-Activated Kinases in Cancer and Beyond: Where Are We Heading?

“…Due to the distinct and overlapping functions of PAKs, the pan-PAK inhibitors may cause undesirable PK characteristics, consequent lack of tumor responses, and adverse side effects (mainly on cardiovascular and gastrointestinal function), leading to the termination of PF-3758309 clinical trial (Crawford et al, 2012;Rudolph et al, 2016;Rane and Minden, 2019). So far, just the KPT-9274, a PAK4 and NAMPT dual inhibitor, is ongoing in phase I clinical trials (NCT02702492 and NCT04281420) for solid tumors and non-Hodgkin's lymphoma (NHL) (Abu Aboud et al, 2016;Li et al, 2019;Cordover et al, 2020). Recently, CP734, a small molecule, was found to target PAK1 ATPase activity by binding to V342 of PAK1 (Wang et al, 2020).…”

Advances in NAD-Lowering Agents for Cancer Treatment

“…The novel NAMPT/PAK4 inhibitor, KPT-9274, elicited remarkable antitumor effects in a broad panel of tumor mouse models, including models of renal cell carcinoma [ 118 ], B-cell acute lymphoblastic leukemia [ 194 ], acute myeloid leukemia [ 169 ], melanoma [ 158 ], colon cancer [ 158 ], triple-negative breast cancer [ 195 ], pancreatic ductal adenocarcinoma [ 161 ], pancreatic neuroendocrine tumors [ 160 ], rhabdomyosarcoma [ 196 ], Ewing sarcoma [ 197 ], multiple myeloma [ 198 ], and Waldenstrom macroglobulinemia [ 159 ]. It should be mentioned that the antitumor activity of KPT-9274 in rhabdomyosarcoma, Ewing sarcoma, multiple myeloma, breast cancer, pancreatic ductal adenocarcinoma, colon carcinoma, and melanoma was shown to be substantially driven by PAK4 inhibition [ 158 , 161 , 195 , 196 , 197 , 198 , 199 ]. Overall, compelling results from preclinical studies of KPT-9274 and OT-82 (summarized in Table 3 ) built a strong rationale for the evaluation of these two inhibitors in the clinic.…”

Signaling pathways downstream to receptor tyrosine kinases: targets for cancer treatment

“…Recently, KPT-9274 was not only shown to lead to inhibition of Pak4 and NAMPT in triple negative breast cancer cells, but also inhibition of Rictor [121] . Rictor is an important component of mTORC2, Conversely, mouse mammary epithelial cells overexpressing Pak4 had an increase in Rictor activity [121,122] . AKT phosphorylation at Ser473 was dramatically decreased in response to KPT-9274 treatment, also a hallmark of mTORC2 activation.…”