Multi-kinase inhibitors interact with sildenafil and ERBB1/2/4 inhibitors to kill tumor cellsin vitroandin vivo

Abstract

We have recently demonstrated that multi-kinase inhibitors such as sorafenib and pazopanib can suppress the detection of chaperones by in situ immuno-fluorescence, which is further enhanced by phosphodiesterase 5 inhibitors. Sorafenib and pazopanib inhibited the HSP90 ATPase activity with IC50 values of ~1.0 μM and ~75 nM, respectively. Pazopanib docked in silico with two possible poses into the HSP90 ATP binding pocket. Pazopanib and sildenafil combined to reduce the total protein levels of HSP1H/p105 and c-MYC and to reduce their co-localization. Sorafenib/pazopanib combined with sildenafil in a [GRP78+HSP27] –dependent fashion to: (i) profoundly activate an eIF2α/Beclin1 pathway; (ii) profoundly inactivate mTOR and increase ATG13 phosphorylation, collectively resulting in the formation of toxic autophagosomes. In a fresh PDX isolate of NSCLC combined knock down of [ERBB1+ERBB3] or use of the ERBB1/2/4 inhibitor afatinib altered cell morphology, enhanced ATG13 phosphorylation, inactivated NFκB, and further enhanced [sorafenib/pazopanib + sildenafil] lethality. Identical data to that with afatinib were obtained knocking down PI3K p110α/β or using buparlisib, copanlisib or the specific p110α inhibitor BYL719. Afatinib adapted NSCLC clones were resistant to buparlisib or copanlisib but were more sensitive than control clones to [sorafenib + sildenafil] or [pazopanib + sildenafil]. Lapatinib significantly enhanced the anti-tumor effect of [regorafenib + sildenafil] in vivo; afatinib and BYL719 enhanced the anti-tumor effects of [sorafenib + sildenafil] and [pazopanib] in vivo, respectively.

The HDAC inhibitor AR42 interacts with pazopanib to kill trametinib/dabrafenib-resistant melanoma cells in vitro and in vivo

“…Prior studies have demonstrated that pazopanib is an inhibitor of the chaperones HSP90 and HSP70 that was associated with a tertiary structural change in the NH2-termini of the proteins [7, 11]. Using vemurafenib resistant TPF-12-293 cells we re-confirmed that pazopanib could alter the structure of chaperones in melanoma cells as judged by reduced immuno-fluorescence at the NH2-termini but not at their COOH termini (Supplementary Figure 5).…”

“…ATPase inhibition was associated with conformational changes in the ATP binding NH 2 -termini of the chaperone proteins and with the abilities of these chaperones to associate and co-localize with other chaperones and client proteins [7, 8]. It has also been reported that acetylation can also alter the activity of chaperones, generally thought to be an inhibitory effect, with the regulatory acetylation of HSP90 controlled by HDAC6 [9, 10].…”

“…Recently we determined that that phosphodiesterase 5 inhibitors such as sildenafil (Viagra ® ), via PKG signaling, did not significantly alter basal chaperone ATPase activities but instead facilitated sorafenib and pazopanib to cause further inhibition of chaperone ATPase activities and a more rapid NH 2 -terminus conformational change [11]. The changes in chaperone ATPase activity and conformation after [sorafenib + sildenafil] and [pazopanib + sildenafil] exposure was also reflected in the phosphorylation/activity of key chaperoned proteins [7, 8, 11]. Whether chaperone acetylation also facilitates the chaperone inhibitory effects of a multi-kinase inhibitor is unknown.…”

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

“…In several prior publications we have shown that both the HDAC inhibitor sodium valproate (Depakote®) and the PDE5 inhibitor sildenafil (Viagra®) can enhance the formation of autophagosomes and autolysosomes caused by other agents, which in turn leads to elevated levels of tumor cell killing. [10][11][12] Thus, we next determined whether valproate or sildenafil could enhance "autophagy" and thus the lethality of [neratinib + palbociclib].…”

PDE5 inhibitors enhance the lethality of [pemetrexed + sorafenib]

“…PDE5 is expressed in the wider vasculature and myocardium [11]. Tumor cells can over-express PDE5, as we have demonstrated in hepatoma, breast and NSCLC [7, 9]. PDE5 inhibitors have a well-established safety record and have been shown to be safe in combination with most other medications [12, 13].…”