Proteasome inhibition with bortezomib is a validated approach to the treatment of multiple myeloma, but drug resistance often emerges and limits its utility in the retreatment setting. To begin to identify some of the mechanisms involved, we developed bortezomib-resistant myeloma cell lines that, unlike previously reported models, showed no ␤5 subunit mutations. Instead, up-regulation of the insulinlike growth factor (IGF)-1 axis was identified, with increased autocrine and paracrine secretion of IGF-1, leading to increased activation of the IGF-1 receptor (IGF-1R). Exogenous IGF-1 reduced cellular sensitivity to bortezomib, whereas pharmacologic or small hairpin RNAmediated IGF-1R suppression enhanced bortezomib sensitivity in cell lines and patient samples. In vitro studies with OSI-906, a clinically relevant dual IGF-1R and insulin receptor inhibitor, showed it acted synergistically with bortezomib, and potently resensitized bortezomib-resistant cell lines and patient samples to bortezomib. Importantly, OSI-906 in combination with bortezomib also overcame bortezomib resistance in an in vivo model of myeloma. Taken together, these data support the hypothesis that signaling through the IGF-1/IGF-1R axis contributes to acquired bortezomib resistance, and provide a rationale for combining bortezomib with IGF-1R inhibitors like OSI-906 to overcome or possibly prevent the emergence of bortezomib-refractory disease in the clinic. (Blood. 2012;120(16):3260-3270) IntroductionMultiple myeloma is a malignancy of immunoglobulin-secreting clonal plasma cells that is most often found in the bone marrow. 1,2 Modulation of the activity of the ubiquitin-proteasome pathway with the small molecule proteasome inhibitor bortezomib (VEL-CADE) has been validated as a rational therapeutic strategy for this disease 3,4 both in the front-line and relapsed/refractory settings. Despite these and other advances, myeloma remains an incurable disease characterized by decreasing response durations with each subsequent salvage therapy. 5 This is mediated in part through both intrinsic and acquired drug resistance, the latter of which emerges during and after bortezomib therapy. 6 Response rates in patients with previously bortezomib-sensitive disease are typically decreased on drug rechallenge 7-9 and may be as low as 23% among patients who had achieved at least a partial remission previously. 7 These findings indicate a need for an understanding of the molecular basis for bortezomib resistance.Proteasome inhibition acutely activates multiple inducible chemoresistance pathways that reduce the efficacy of bortezomib. One example is the antiapoptotic Akt pathway that can be activated by proteasome inhibitors, 10 and suppression of this pathway can induce chemosensitization to bortezomib. [11][12][13] Another possible mechanism aiding in acquired resistance to bortezomib may be the development of mutations in the bortezomib-binding pocket of the ␤5 proteasome subunit, or increased expression of ␤5 itself. [14][15][16] However, ␤5 proteasome sub...

Apoptosis is recognized as a predictor of adverse outcomes in subjects with cardiac diseases. The aim of this study was to explore the effects of probiotic-fermented purple sweet potato yogurt (PSPY) with high γ-aminobutyric acid (GABA) content on cardiac apoptosis in spontaneously hypertensive rat (SHR) hearts. The rats were orally adminsitered with 2 different concentrations of PSPY (10 and 100%) or captopril, 15.6 mg/kg, body weight (BW)/day. The control group was administered distilled water. DAPI and TUNEL staining were used to detect the numbers of apoptotic cells. A decrease in the number of TUNEL-positive cardiac myocytes was observed in the SHR-PSPY (10 and 100%) groups. In addition, the levels of key components of the Fas receptor- and mitochondrial-dependent apoptotic pathways were determined by western blot analysis. The results revealed that the levels of the key components of the Fas receptor- and mitochondrial-dependent apoptotic pathway were significantly decreased in the SHR-captopril, and 10 and 100% PSPY groups. Additionally, the levels of phosphorylated insulin-like growth factor‑I receptor (p-IGF‑IR) were increased in SHR hearts from the SHR-control group; however, no recovery in the levels of downstream signaling components was observed. In addition, the levels of components of the compensatory IGF-IR-dependent survival pathway (p-PI3K and p-Akt) were all highly enhanced in the left ventricles in the hearts form the SHR-10 and 100% PSPY groups. Therefore, the oral administration of PSPY may attenuate cardiomyocyte apoptosis in SHR hearts by activating IGF‑IR-dependent survival signaling pathways.

Cardiovascular hypertrophy is a common feature of hypertension and an important risk factor for heart damage. The regression of cardiovascular hypertrophy is currently considered an important therapeutic target in reducing the omplications of hypertension. The aim of this study was to investigate the inhibition of cardiac hypertrophy by probiotic-fermented purple sweet potato yogurt (PSPY) with high γ-aminobutyric acid (GABA) content in spontaneously hypertensive rat (SHR) hearts. Six-week-old male SHRs were separated randomly and equally into 4 experimental groups: sterile water, captopril and 2 PSPY groups with different doses (10 and 100%) for 8 weeks. The changes in myocardial architecture and key molecules of the hypertrophy-related pathway in the excised left ventricle from these rats were determined by histopathological analysis, hematoxylin and eosin staining and western blot analysis. Abnormal myocardial architecture and enlarged interstitial spaces observed in the SHRs were significantly decreased in the captopril and PSPY groups compared with the sterile water group. Moreover, the increases in atrial natriuretic peptide, B-type natriuretic peptide, phosphorilated protein kinase Cα and calmodulin-dependent protein kinase II levels in the left ventricle were accompanied by hypertension and increases in phosphorylated extracellular signal-regulated kinase 5 activities with enhanced cardiac hypertrophy. However, the protein levels of the hypertrophic-related pathways were completely reversed by the administration of PSPY. PSPY may repress the activation of ANP and BNP which subsequently inhibit the dephosphorylation of the nuclear factor of activated T-cells, cytoplasmic 3 and ultimately prevent the progression of cardiac hypertrophy.

Inflammation plays an important role in triggering fibrosis of cardiovascular disease and hypertension. Gamma-aminobutyric acid (GABA) has hypotensive effect; GABA concentration could be enhanced in milk fermented with lactic acid bacteria (LAB). This study evaluated the effect of probiotic-fermented purple sweet potato yogurt (PSPY) on the toll-like receptor 4 (TLR-4)-related inflammatory components, and on fibrosis in the heart of spontaneously hypertensive rat (SHR). TLR4-related pathway and fibrosis-associated proteins TGFbeta and FGF2 were significantly increased in SHR hearts, but were highly suppressed in 10% PSPY-fed rats. Microscopic examination with Masson trichrome staining of left ventricle further demonstrated that 10% and 100% PSPY both significantly reduced interstitial fibrosis in SHR hearts. These findings indicated that oral administration of 10% probiotic-fermented PSPY was strong enough to lower cardiac fibrosis in SHR rats through the suppression of TLR-4-related inflammatory pathway. Therefore, PSPY may be included in diets to help prevent cardiac fibrosis in patients with hypertension.

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