Nucleophosmin (NPM), a multifunctional nucleolar phosphoprotein is dysregulated in human malignancies leading to anti-apoptosis and inhibition of differentiation.We evaluated the precise three-dimensional structure of NPM based on the highly conserved structure of Xenopus NO38 and its requirement to form dimers and pentamers via its N-terminal domain (residues, 1-107). We hypothesized that a small molecular inhibitor (SMI) that could disrupt the formation of dimers would inhibit aberrant NPM function(s) in cancer cells. Molecular modeling, pharmacophore design, in silico screening and interactive docking identified NSC348884 as a putative NPM SMI that disrupts a defined hydrophobic pocket required for oligomerization. NSC348884 inhibited cell proliferation at an IC 50 of 1.7-4.0 lM in distinct cancer cell lines and disrupted NPM oligomer formation by native polyacrylamide gel electrophoresis assay. Treatment of several different cancer cell types with NSC348884 upregulated p53 (increased Ser15 phosphorylation) and induced apoptosis in a dose-dependent manner that correlated with apoptotic markers: H2AX phosphorylation, poly(ADPribose) polymerase cleavage and Annexin V labeling. Further, NSC348884 synergized doxorubicin cytotoxicity on cancer cell viability. The data together show that NSC348884 is an SMI of NPM oligomer formation, upregulates p53, induces apoptosis and synergizes with chemotherapy. Hence, an SMI to NPM may be a useful approach to anticancer therapy.
Purpose Aurora A and B are oncogenic serine/threonine kinases that regulate mitosis. Over-expression of Auroras promotes resistance to microtubule targeted agents. We investigated mechanistic synergy by inhibiting the mitotic spindle apparatus in the presence of MLN8237 [M], an Aurora A inhibitor with either vincristine [MV] or docetaxel [MD] in aggressive B-NHL. The addition of rituximab [R] to MV or MD was evaluated for synthetic lethality. Experimental Design Aggressive B-NHL cell subtypes were evaluated in vitro and in vivo for target modulation and anti-NHL activity with single agents, doublets and triplets by analyzing cell proliferation, apoptosis, tumor growth, survival and mechanisms of response/relapse by gene expression profiling with protein validation. Results MV is synergistic while MD is additive for cell proliferation inhibition in B-NHL cell culture models. Addition of R to MV is superior to MD but both significantly induce apoptosis compared to doublet therapy. Mouse xenograft models of mantle cell lymphoma showed modest single agent activity for M, R, D and V with tumor growth inhibition (TGI) of ~10–15%. Of the doublets, MV caused tumor regression, while TGI was observed with MD (~55–60%) and MR (~25–50%) respectively. Although MV caused tumor regression, mice relapsed 20 days after stopping therapy. In contrast, MVR was curative, while MDR led to TGI of ~85%. PCNA, Aurora B, cyclin B1, cyclin D1 and Bcl-2 proteins of harvested tumors confirmed response and resistance to therapy. Conclusions Addition of R to MV is a novel therapeutic strategy for aggressive B-NHL and warrants clinical trial evaluation.
BackgroundProstate cancer is a common disease in men and at present there is no effective therapy available due to its recurrence despite androgen deprivation therapy. The epidermal growth factor receptor family (EGFR/HER1, HER2/neu and HER3)/PI3K/Akt signaling axis has been implicated in prostate cancer development and progression. However, Erlotinib, an EGFR tyrosine kinase inhibitor, has less effect on proliferation and apoptosis in prostate cancer cell lines. In this study, we evaluate whether MP470, a novel receptor tyrosine kinase inhibitor alone or in combination with Erlotinib has inhibitory effect on prostate cancer in vitro and in vivo.MethodsThe efficacy of MP470 or MP470 plus Erlotinib was evaluated in vitro using three prostate cancer cell lines by MTS and apoptosis assays. The molecular mechanism study was carried out by phosphorylation antibody array, immunoblotting and immunohistochemistry. A LNCaP mouse xenograft model was also used to determine the tumor growth inhibition by MP470, Erlotinib or the combination treatments.ResultsMP470 exhibits low μM IC50 in prostate cancer cell lines. Additive effects on both cytotoxicity and induction of apoptosis were observed when LNCaP were treated with MP470 in combination with Erlotinib. This combination treatment completely inhibited phosphorylation of the HER family members (HER1, 2, 3), binding of PI3K regulatory unit p85 to HER3 and downstream Akt activity even after androgen depletion. Furthermore, in a LNCaP mouse xenograft model, the MP470-Erlotinib combination produced 30–65% dose-dependent tumor growth inhibition (TGI).ConclusionWe propose that MP470-Erlotinib targets the HER family/PI3K/Akt pathway and may represent a novel therapeutic strategy for prostate cancer.
Background: c-Kit/α-PDGFR targeted therapies are effective for gastrointestinal stromal tumors (GIST), but, >50% develop drug resistance.Methods: RTK expression (c-Kit, c-Met, AXL, HER-1, HER-2, IGF-1R) in pre-/post-imatinib (IM) GIST patient samples (n=16) and 4 GIST cell lines were examined for RTK inhibitor activity. GIST-882 cells were cultured in IM every other day, cells collected (1 week to 6 months) and analyzed by qRT-PCR and Western blotting.Results: Immunohistochemistry pre-/post-IM demonstrated continued expression of c-Kit and HER1, while a subset expressed IGF-1R, c-Met and AXL. In GIST cells (GIST-882, GIST430/654, GIST48) c-Kit, HER1 and c-Met are co-expressed. Acute IM over-express c-Kit while chronic IM, lose c-Kit and HER-1 in GIST882 cells. GIST882 and GIST430/654 cells have an IC50 0.077 and 0.59 μM to IM respectively. GIST48 have an IC50 0.66 μM to IM, 0.91 μM to amuvatinib [AMU] and 0.67 μM to erlotinib (Erl). Synergistic combinations: GIST882, AMU + Erl (CI 0.20); IM + AMU (CI 0.50), GIST430/654, IM + afatinib (CI 0.39); IM + AMU (CI 0.42), GIST48, IM + afatinib (CI 0.03); IM + AMU (CI 0.04); AMU + afatinib (CI 0.36); IM + Erl (CI 0.63).Conclusion: Targeting c-Kit plus HER1 or AXL/c-Met abrogates IM resistance in GIST.
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