Antiproliferative effects of Bortezomib in endothelial cells transformed by viral G protein-coupled receptor associated to Kaposi's sarcoma

Bortezomib Is Effective in the Treatment of T Lymphoblastic Leukaemia by Inducing DNA Damage, WEE1 Downregulation, and Mitotic Catastrophe

T lymphoblastic leukemia (T-ALL) is an aggressive haematolymphoid malignancy comprising 15% of acute lymphoblastic leukemia (ALL). Although its prognosis has improved with intensive chemotherapy, the relapse/refractory disease still carries a dismal prognosis. Thus, there is an urgent need to develop novel therapy for T-ALL. Bortezomib, a 26S proteasome inhibitor, is licensed to treat plasma cell myeloma and mantle cell lymphoma. Due to its favorable side effect profile, it is a novel agent of research interest in the treatment of ALL. Despite an increasing number of clinical trials of bortezomib in T-ALL, its detailed mechanistic study in terms of DNA damage, cell cycle, and mitotic catastrophe remains elusive. Moreover, WEE1, a protein kinase overexpressed in ALL and involved in cell-cycle regulation, has been known to be a novel therapeutic target in many cancers. But the role of bortezomib in modulating WEE1 expression in ALL still remains elusive. In this study, we demonstrate the therapeutic efficacy of bortezomib on T-ALL primary samples and cell lines. Our findings reveal that bortezomib treatment induces DNA damage and downregulates WEE1, leading to G2-M cell-cycle progression with damaged DNA. This abnormal mitotic entry induced by bortezomib leads to mitotic catastrophe in T-ALL. In conclusion, our findings dissect the mechanism of action of bortezomib and provide further insights into the use of bortezomib to treat T-ALL. Our findings suggest the possibility of novel combination therapy using proteasome inhibitors together with DNA-damaging agents in the future, which may fill the research gaps and unmet clinical needs in treating ALL.

1α,25(OH)2D3 regulates pro-angiogenic factors in endothelial cells transformed by Kaposi's sarcoma-associated herpesvirus G protein coupled receptor

When tumoral cell expansion exceeds the vascular supply, regions of hypoxia or low oxygen concentration are generated promoting the formation of new vessels through cell proliferation and migration. Viral G protein-coupled receptor (vGPCR) is associated to Kaposi's sarcoma pathology and induces a paracrine transformation when is stably expressed in murine endothelial cells activating hypoxia-induced transcription factors. Previously, we reported the antiproliferative actions of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) in endothelial cells transformed by the vGPCR (SVEC-vGPCR). Herein, we further investigated if pro-angiogenic factors as AP-1, HIF-1α and VEGF are modulated by 1α,25(OH)2D3. We found by qRT-PCR analysis that the mRNA level of JunB, a negative regulator of cell proliferation, was similarly increased at all-time points tested after 1α,25(OH)2D3 treatment in SVEC-vGPCR cells. Also, mRNA levels of the pro-angiogenic factor c-Fos, which induces tumor invasion, were only decreased during one short period treatment. In addition, Hif-1α mRNA and protein levels were significantly reduced after 1α,25(OH)2D3 treatment in a VDR dependent fashion. However, mRNA levels of the angiogenic activator Vegf, promoted in turn by Hif-1α expression, were surprisingly high depending on VDR expression as well. Moreover, Egr-1, which has been reported to induce VEGF expression independently of HIF-1α, diminished its expression with 1α,25(OH)2D3 treatment, fact that was related to the decline of p-ERK1/2. Altogether, these results suggest a negative modulation of some pro-angiogenic factors like AP-1 and HIF-1α, as part of the antiproliferative mechanism of 1α,25(OH)2D3 in SVEC-vGPCR endothelial cells.

Down-regulation of COX-2 activity by 1α,25(OH)2D3 is VDR dependent in endothelial cells transformed by Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor

Our previous reports showed that 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) has antiproliferative actions in endothelial cells stably expressing viral G protein-coupled receptor (vGPCR) associated with the pathogenesis of Kaposi's sarcoma. It has been reported that COX-2 enzyme, involved in the tumorigenesis of many types of cancers, is induced by vGPCR. Therefore, we investigated whether COX-2 down-regulation is part of the growth inhibitory effects of 1α,25(OH)2D3. Proliferation was measured in presence of COX-2 inhibitor Celecoxib (10-20 μM) revealing a decreased in vGPCR cell number, displaying typically apoptotic features in a dose dependent manner similarly to 1α,25(OH)2D3. In addition, the reduced cell viability observed with 20 μM Celecoxib was enhanced in presence of 1α,25(OH)2D3. Remarkably, although COX-2 mRNA and protein levels were up-regulated after 1α,25(OH)2D3 treatment, COX-2 enzymatic activity was reduced in a VDR-dependent manner. Furthermore, an interaction between COX-2 and VDR was revealed through GST pull-down and computational analysis. Additionally, high-affinity prostanoid receptors (EP3 and EP4) were found down-regulated by 1α,25(OH)2D3. Altogether, these results suggest a down-regulation of COX-2 activity and of prostanoid receptors as part of the antineoplastic mechanism of 1α,25(OH)2D3 in endothelial cells transformed by vGPCR.

Angiotensin II-upregulated MAP kinase phosphatase-3 modulates FOXO1 and p21 in adrenocortical H295R cells

MAPK phosphatases (MKP) downregulate the activity of mitogen-activated protein kinases (MAPK), such as ERK1/2, and modulate the processes regulated by these kinases. ERK1/2 participate in a wide range of processes including tissue-specific hormone-stimulated steroidogenesis. H295R cells are a suitable model for the study of human adrenal cortex functions, particularly steroid synthesis, and respond to angiotensin II (Ang II) triggering ERK1/2 phosphorylation in a transient fashion. MKP-3 dephosphorylates ERK1/2 and, as recently reported, forkhead box protein 1 (FOXO1). Here, we analyzed MKP-3 expression in H295R cells and its putative regulation by Ang II. Results showed the expression of MKP-3 full length (L) and a short splice variant (S), and the upregulation of both isoforms by Ang II. L and S messenger and protein levels increased 30 min after Ang II stimulation and declined over the next 3 h, a temporal frame compatible with ERK1/2 dephosphorylation. In addition, FOXO1 activation is known to include its dephosphorylation and nuclear translocation. Therefore, we analyzed the effect of Ang II on FOXO1 modulation. Ang II induced FOXO1 transient phosphorylation and translocation and also the induction of p21, a FOXO1-dependent gene, whereas MKP-3 knock-down reduced both FOXO1 translocation and p21 induction. These data suggest that, through MKP-3, Ang II counteracts its own effects on ERK1/2 activity and also triggers the activation of FOXO-1 and the induction of cell cycle inhibitor p21. Taken together, the current findings reveal the participation of MKP-3 not only in turn–off but also in turn-on signals which control important cellular processes.

Pilot Trial AMC-063: Safety and Efficacy of Bortezomib in AIDS-associated Kaposi Sarcoma

PURPOSE

AIDS-related Kaposi sarcoma is often incompletely controlled, requiring serial therapies. Kaposi sarcoma herpesvirus (KSHV) induces transformation of endothelial cells, where it resides in a predominately latent state. We hypothesized proteasome inhibition would have direct antitumor activity, induce lytic activation of KSHV, and inhibit HIV infectivity, improving control of both Kaposi sarcoma and HIV. The primary objective was determining the MTD of bortezomib in AIDS-Kaposi sarcoma. Secondary objectives included estimating the impact of bortezomib on Kaposi sarcoma response, KSHV plasma DNA copy number (PDCN), and HIV viral loads (VL).

PATIENTS AND METHODS

A 3+3 dose escalation design was employed evaluating four dose levels of bortezomib (0.75, 1, 1.2, or 1.6 mg/m2) administered intravenously on days 1, 8, and 15 of 28-day cycles in patients with relapsed/refractory (r/r) AIDS-Kaposi sarcoma taking antiretroviral therapy.

RESULTS

Seventeen patients enrolled. No dose-limiting toxicities occurred and the MTD was not reached. The most common adverse events included diarrhea, fatigue and nausea. Among 15 evaluable patients, partial response (PR) occurred in nine (60%), with a PR rate of 83% in the 1.6 mg/m2 cohort; the remainder had stable disease (SD). Median time to response was 2.1 months. Median change in KSHV PDCN was significantly different between those with PR versus SD. During cycle 1, seven of 11 evaluable patients had decreases in HIV VL.

CONCLUSIONS

Bortezomib is well-tolerated and active in AIDS-Kaposi sarcoma. The 60% PR rate is notable given the dose-finding nature of the study in a r/r population. Changes in KSHV PDCN and HIV VL trended as hypothesized.

In vitro studies revealed a downregulation of Wnt/β-catenin cascade by active vitamin D and TX 527 analog in a Kaposi's sarcoma cellular model

The Kaposi's sarcoma-associated herpesvirus G-protein-coupled receptor (vGPCR) is a key molecule in the pathogenesis of Kaposi's sarcoma. We have previously demonstrated that 1α,25(OH)₂D₃ or its less calcemic analog TX 527 exerts antiproliferative effects in endothelial cells stable expressing vGPCR. Since it is well documented that vGPCR activates the canonical Wnt/β-catenin signaling pathway, the aim of this study was to evaluate if Wnt/β-catenin cascade is target of 1α,25(OH)₂D₃ or TX 527 as part of their antineoplastic mechanism. Firstly, Western blot studies showed an increase in β-catenin protein levels in a dose and time dependent manner; and when VDR was knockdown, β-catenin protein levels were significantly decreased. Secondly, β-catenin localization, investigated by immunofluorescence and subcellular fractionation techniques, was found increased in the nucleus and plasma membrane after 1α,25(OH)₂D₃ treatment. VE-cadherin protein levels were also increased in the plasma membrane fraction. Furthermore, β-catenin interaction with VDR was observed by co-immunoprecipitation and mRNA expression of β-catenin target genes was found decreased. Finally, DKK-1, the extracellular inhibitor of Wnt/β-catenin pathway, showed an initial upregulation of mRNA expression. Altogether, the results obtained by different techniques revealed a downregulation of Wnt/β-catenin cascade after 1α,25(OH)₂D₃ or TX 527 treatment, showing the foundation for a potential chemotherapeutic agent.

VDR agonists down regulate PI3K/Akt/mTOR axis and trigger autophagy in Kaposi's sarcoma cells

The Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor (KSHV/vGPCR) is a key molecule in the pathogenesis of Kaposi's sarcoma. We have previously shown that 1α,25(OH)2D3 or its less-calcemic analog TX 527 inhibits the proliferation of endothelial cells expressing vGPCR, NF-κB activity and induces apoptosis in a VDR dependent manner. In this work, we further explored whether 1α,25(OH)2D3 or TX 527 regulates PI3K/Akt/mTOR axis and induces autophagy as part of its antineoplastic mechanism of action. Proliferation assays indicated that vGPCR cell number decreased in presence of LY294002 (PI3K/Akt inhibitor) likewise 1α,25(OH)2D3 or TX 527 (10 nM, 48 h). Also, Akt phosphorylation was found decreased in dose (0.1-100 nM) and time response studies (12-72 h) after both compounds treatments. In addition, decreased phosphorylated Akt was significantly observed in the nucleus. Moreover, regulation of Akt phosphorylation was NF-κB and VDR dependent. TNFAIP3/A20, an ubiquitin-editing enzyme, a direct NF-κB target gene and a negative regulator of Beclin-1, was down-regulated whereas Beclin-1 was up-regulated after 10 nM of 1α,25(OH)2D3 or TX 527 treatment. Decrement in Akt phosphorylation was accompanied by a reduced mTOR phosphorylation and an increase in the autophagy marker LC3-II. Since increment in autophagosomes not always indicates increment in autophagy activity, we used Chloroquine (CQ, 1 μM), an inhibitor of autophagy flow, to confirm autophagy after both VDR agonists treatment. In conclusion, VDR agonists, 1α,25(OH)2D3 or TX 527, inhibited PI3K/Akt/mTOR axis and induced autophagy in endothelial cells expressing vGPCR by a VDR-dependent mechanism.

Antineoplastic effect of 1α,25(OH)2D3 in spheroids from endothelial cells transformed by Kaposi's sarcoma-associated herpesvirus G protein coupled receptor

The Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor (KSHV/vGPCR) is a key molecule in the pathogenesis of Kaposi's sarcoma. In endothelial cells, tumor maintenance and NF-κB activation depends on vGPCR constitutive expression and activity. We have previously demonstrated that 1α,25(OH)₂D₃ induces apoptosis in a VDR dependent manner, inhibits vGPCR cell growth and NF-κB activity. In this study, we developed a method to obtain multicellular spheroids (MCS) from endothelial cells expressing vGPCR in order to test whether MCS have a similar response to 2D-cultures after 1α,25(OH)₂D₃ treatment. Firstly, we found that vGPCR MCS started to form at 2^nd day-growth, reaching a diameter up to 300 μm at 7^th day-growth, whereas cells without vGPCR expression (SVEC) developed spheroids earlier and remained smaller throughout the period monitored. Secondly, vGPCR MCS size and architecture were analyzed during 1α,25(OH)₂D₃ (0.1-100 nM, 48 h) treatment. We found that once treated with 10 nM of 1α,25(OH)₂D₃ the initials MCS began a slight disaggregation with no changes in size; whereas at the higher dose (100 nM) the architecture of MCS was found completely broken. Furthermore, VDR mRNA expression increased significantly and this change was accompanied by a reduction of HIF-1α, an increase of VEGF, p21 and Bim mRNA expression. Finally, results from Western blot analysis showed that 1α,25(OH)₂D₃ decreased Akt and ERK1/2 protein phosphorylation. In conclusion, these data have revealed that 1α,25(OH)₂D₃ inhibits vGPCR MCS proliferation and induces apoptosis similar to vGPCR cells growing in 2D-cultures.

Synergistic apoptosis of human gastric cancer cells by bortezomib and TRAIL

Resistance against tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell death of cancer cells is a major obstacle in clinical application of TRAIL. Variable response to TRAIL of gastric cancer cells, synergy of TRAIL with bortezomib and potential mechanisms behind the phenomena were investigated in this study. The response to TRAIL varied among six gastric cancer cell lines, which correlated with the expression of apoptotic TRAIL receptors. Analysis of TCGA gene expression data showed that DR4 expression correlated with DR5 in gastric cancer. Although higher expression of DR4 was significantly associated with lower T, N and TNM stages, neither DR4 nor DR5 expression meaningfully influenced overall survival rate. Combined treatment of TRAIL with bortezomib resulted in strong synergistic response with enhanced activation of caspases-8, -9 and -3, and increased Annexin V-binding cell fractions in TRAIL-resistant SNU-216 cells. Bortezomib increased the expression of p21^cip1/waf1, but p21^cip1/waf1 silencing did not restore cell viability significantly. Bortezomib also increased DR5 expression and knockdown of DR5 expression significantly recovered cell viability reduced by the combination treatment. Bortezomib decreased phosphorylation of ERK1/2, but increased that of JNK. Treatment with either an ERK1/2 inhibitor U0126 or a JNK inhibitor SP600125 rescued SNU-216 from dying of bortezomib or combined treatment. However, upregulation of DR5 by bortezomib was knocked down only by inhibition of ERK1/2 activation significantly, but not by JNK activity inhibition. In summary, upregulation of DR5 by bortezomib is of critical significance in the synergy of bortezomib with TRAIL in apoptosis of TRAIL-resistant SNU-216 and that activity of ERK1/2 is required in the bortezomib-induced DR5 overexpression.