Palbociclib augments Neratinib killing of tumor cells that is further enhanced by HDAC inhibition

Abstract

Cancers expressing mutant RAS are associated with a weaker response to chemotherapy and a shorter overall patient survival. We have demonstrated that the irreversible inhibitor of ERBB1/2/4, neratinib, inhibits ERBB1/2/4 and causes their internalization and autolysosomal degradation. Fellow-traveler membrane proteins with RTKs, including mutant K-/N-RAS, were also degraded. We discovered that the CDK4/6 inhibitor palbociclib increased autophagosome and then autolysosome levels in a time dependent fashion, did not reduce mTOR activity, and interacted with temsirolimus to kill. Neratinib and palbociclib interacted in a greater than additive manner to increase autophagosome and then autolysosome levels in a time dependent fashion, and to cause tumor cell killing. Killing required the expression of ATM and AMPKα, Beclin1 and ATG5, BAX and BAK and of AIF, but not of caspase 9. In some cells over-expression of BCL-XL was protective whereas in others it was ineffective. The lethality of [neratinib + palbociclib] was modestly enhanced by the PDE5 inhibitor sildenafil and strongly enhanced by the HDAC inhibitor sodium valproate. This was associated with K-RAS degradation and a greater than additive increase in autophagosome and autolysosome levels. Killing by the three-drug combination required ATM and AMPKα, and, to a greater extent, Beclin1 and ATG5. In vivo, [valproate + palbociclib] and [neratinib + valproate + palbociclib] interacted to suppress the growth of a carboplatin/paclitaxel resistant PDX ovarian tumors that express a mutant N-RAS. Our data support performing a future three-drug trial with these agents.

GZ17‐6.02 initiates DNA damage causing autophagosome‐dependent HDAC degradation resulting in enhanced anti‐PD1 checkpoint inhibitory antibody efficacy

“…All cell lines were cultured at 37°C (5% (v/v CO 2 ) in vitro using RPMI supplemented with 5% (v/v) fetal calf serum and 10% (v/v) nonessential amino acids. Cells were transfected with siRNA molecules or plasmids as described in prior manuscripts (Booth, Roberts, Poklepovic, Gordon, & Dent, 2017; Booth, Roberts, Rais et al, 2017; Booth, Roberts, Poklepovic, et al, 2017; Booth, Roberts, Poklepovic, & Dent, 2017, Booth, Roberts, Sander, et al, 2017; Booth, Roberts, Rais, et al, 2019; Booth, Roberts, Samuel, et al, 2018; Booth, Roberts, Sander, et al, 2019; Booth, Roberts, Poklepovic, & Dent, 2019; Dent, Booth, Roberts, Liu et al, 2019). Cells were transfected with plasmids (0.1 μg) using lipofectamine 2000.…”

Preclinical Characteristics of the Irreversible Pan-HER Kinase Inhibitor Neratinib Compared with Lapatinib: Implications for the Treatment of HER2-Positive and HER2-Mutated Breast Cancer

“…The cytotoxicity of neratinib can be enhanced by HDAC inhibitors, with the added benefit that this combination has been shown to improve the anti-tumor immune response in preclinical models of afatinib-resistant non-small cell lung and breast cancers [125]. Addition of the cyclin-dependent kinase (CDK)4/6 inhibitor palbociclib to neratinib plus the HDAC inhibitor valproate suppressed growth of a patient-derived platinum/taxane-resistant ovarian xenograft model [126]. Neratinib plus valproate also enhanced the efficacy of a programmed cell death-1 (PD-1) antibody in a mouse syngeneic breast cancer model [125].…”

Selective CDK4/6 Inhibitors: Biologic Outcomes, Determinants of Sensitivity, Mechanisms of Resistance, Combinatorial Approaches, and Pharmacodynamic Biomarkers

“…In the case of CDK4/6 inhibition, there is a shift toward oxidative [73][74][75] or autophagic metabolism. 53,76 These findings could be leveraged using selective inhibitors targeting these processes to essentially shift the cytostatic state induced by CDK4/6 inhibit into a selective vulnerability. 53 Similarly, because RB activation can limit the expression of multiple DNA repair-associated genes, treatment with CDK4/6 inhibitors could yield a functional state similar to multiple forms of DNA repair deficiency, which ostensibly can be exploited by chemotherapy or radiation therapy.…”