Therapies targeting estrogen receptor α (ERα, encoded by ESR1) have transformed the treatment of breast cancer. However, large numbers of women relapse, highlighting the need for the discovery of new regulatory targets modulating ERα pathways. An siRNA screen identified kinases whose silencing alters the estrogen response including those previously implicated in regulating ERα activity (such as mitogen-activated protein kinase and AKT). Among the most potent regulators was lemur tyrosine kinase-3 (LMTK3), for which a role has not previously been assigned. In contrast to other modulators of ERα activity, LMTK3 seems to have been subject to Darwinian positive selection, a noteworthy result given the unique susceptibility of humans to ERα+ breast cancer. LMTK3 acts by decreasing the activity of protein kinase C (PKC) and the phosphorylation of AKT (Ser473), thereby increasing binding of forkhead box O3 (FOXO3) to the ESR1 promoter. LMTK3 phosphorylated ERα, protecting it from proteasomal degradation in vitro. Silencing of LMTK3 reduced tumor volume in an orthotopic mouse model and abrogated proliferation of ERα+ but not ERα- cells, indicative of its role in ERα activity. In human cancers, LMTK3 abundance and intronic polymorphisms were significantly associated with disease-free and overall survival and predicted response to endocrine therapies. These findings yield insights into the natural history of breast cancer in humans and reveal LMTK3 as a new therapeutic target.

SummaryConstitutive NF-κB signaling promotes survival in multiple myeloma (MM) and other cancers; however, current NF-κB-targeting strategies lack cancer cell specificity. Here, we identify the interaction between the NF-κB-regulated antiapoptotic factor GADD45β and the JNK kinase MKK7 as a therapeutic target in MM. Using a drug-discovery strategy, we developed DTP3, a D-tripeptide, which disrupts the GADD45β/MKK7 complex, kills MM cells effectively, and, importantly, lacks toxicity to normal cells. DTP3 has similar anticancer potency to the clinical standard, bortezomib, but more than 100-fold higher cancer cell specificity in vitro. Notably, DTP3 ablates myeloma xenografts in mice with no apparent side effects at the effective doses. Hence, cancer-selective targeting of the NF-κB pathway is possible and, at least for myeloma patients, promises a profound benefit.

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Oral phosphodiesterase (PDE) 4 inhibitors such as roflumilast have established the potential of PDE4 inhibition for the treatment of respiratory diseases. However, PDE4 inhibitor efficacy is limited by mechanism-related side effects such as emesis and nausea. Delivering the inhibitor by the inhaled route may improve therapeutic index, and we describe 6-, an exceptionally high-affinity inhibitor of PDE4 designed for inhaled administration. GSK256066 is a slow and tight binding inhibitor of PDE4B (apparent IC 50 3.2 pM; steady-state IC 50 Ͻ0.5 pM), which is more potent than any previously documented compound, for example, roflumilast (IC 50 390 pM), tofimilast (IC 50 1.6 nM), and cilomilast (IC 50 74 nM). Consistent with this, GSK256066 inhibited tumor necrosis factor ␣ production by lipopolysaccharide (LPS)-stimulated human peripheral blood monocytes with 0.01 nM IC 50 (compared with IC 50 values of 5, 22, and 389 nM for roflumilast, tofimilast, and cilomilast, respectively) and by LPS-stimulated whole blood with 126 pM IC 50 . GSK256066 was highly selective for PDE4 (Ͼ380,000-fold versus PDE1, PDE2, PDE3, PDE5, and PDE6 and Ͼ2500-fold against PDE7), inhibited PDE4 isoforms A-D with equal affinity, and had a substantial high-affinity rolipram binding site ratio (Ͼ17). When administered intratracheally to rats, GSK256066 inhibited LPS-induced pulmonary neutrophilia with ED 50 values of 1.1 g/kg (aqueous suspension) and 2.9 g/kg (dry powder formulation) and was more potent than an aqueous suspension of the corticosteroid fluticasone propionate (ED 50 9.3 g/kg). Thus, GSK256066 has been demonstrated to have exceptional potency in vitro and in vivo and is being clinically investigated as a treatment for chronic obstructive pulmonary disease.

Following publication of this manuscript, the authors discovered some panels that had been incorrectly cropped in Figures S4H and S5V in the Supplemental Information.As a result of this error, the 0 hr time points of the top PARP-1 panel of Figure S4H, U266, the Tot-JNK and Tot-ERK panels of Figure S5V, U266, and the P-p38 panel of Figure S5V, RPMI-8226, as well as the 0 hr and 0.5 hr, DTP3, time points of the P-ERK panel of Figure S5V, RPMI-8226, were accidentally omitted from these panels. An extra time point (i.e., a 1.5 hr time point, T/I) was also accidentally included in the P-ERK panel of this figure. Due to an analogous error, the P-JNK panel of Figure S5V, RPMI-8226, was incorrectly aligned.The authors also discovered an antibody that had been erroneously omitted from the Supplemental Experimental Procedures. This antibody, anti-PARP-1 (9532S; 1:1,000), should have been included in the section ''Antibodies, Reagents and Western Blots.''