Efficient in vivo genome editing prevents hypertrophic cardiomyopathy in mice

Dominant missense pathogenic variants in cardiac myosin heavy chain cause hypertrophic cardiomyopathy (HCM), a currently incurable disorder that increases risk for stroke, heart failure and sudden cardiac death. In this study, we assessed two different genetic therapies-an adenine base editor (ABE8e) and a potent Cas9 nuclease delivered by AAV9-to prevent disease in mice carrying the heterozygous HCM pathogenic variant myosin R403Q. One dose of dual-AAV9 vectors, each carrying one half of RNA-guided ABE8e, corrected the pathogenic variant in ≥70% of ventricular cardiomyocytes and maintained durable, normal cardiac structure and function. An additional dose provided more editing in the atria but also increased bystander editing. AAV9 delivery of RNA-guided Cas9 nuclease effectively inactivated the pathogenic allele, albeit with dose-dependent toxicities, necessitating a narrow therapeutic window to maintain health. These preclinical studies demonstrate considerable potential for single-dose genetic therapies to correct or silence pathogenic variants and prevent the development of HCM.

Pathogenesis of Cardiomyopathy Caused by Variants in ALPK3, an Essential Pseudokinase in the Cardiomyocyte Nucleus and Sarcomere

BACKGROUND

ALPK3 encodes α-kinase 3, a muscle-specific protein of unknown function. ALPK3 loss-of-function variants cause cardiomyopathy with distinctive clinical manifestations in both children and adults, but the molecular functions of ALPK3 remain poorly understood.

METHODS

We explored the putative kinase activity of ALPK3 and the consequences of damaging variants using isogenic human induced pluripotent stem cell-derived cardiomyocytes, mice, and human patient tissues.

RESULTS

Multiple sequence alignment of all human α-kinase domains and their orthologs revealed 4 conserved residues that were variant only in ALPK3, demonstrating evolutionary divergence of the ALPK3 α-kinase domain sequence. Phosphoproteomic evaluation of both ALPK3 kinase domain inhibition and overexpression failed to detect significant changes in catalytic activity, establishing ALPK3 as a pseudokinase. Investigations into alternative functions revealed that ALPK3 colocalized with myomesin proteins (MYOM1, MYOM2) at both the nuclear envelope and the sarcomere M-band. ALPK3 loss-of-function variants caused myomesin proteins to mislocalize and also dysregulated several additional M-band proteins involved in sarcomere protein turnover, which ultimately impaired cardiomyocyte structure and function.

CONCLUSIONS

ALPK3 is an essential cardiac pseudokinase that inserts in the nuclear envelope and the sarcomere M-band. Loss of ALPK3 causes mislocalization of myomesins, critical force-buffering proteins in cardiomyocytes, and also dysregulates M-band proteins necessary for sarcomere protein turnover. We conclude that ALPK3 cardiomyopathy induces ventricular dilatation caused by insufficient myomesin-mediated force buffering and hypertrophy by impairment of sarcomere proteostasis.

Ablation of lysophosphatidic acid receptor 1 attenuates hypertrophic cardiomyopathy in a mouse model

Myocardial fibrosis is a key pathologic feature of hypertrophic cardiomyopathy (HCM). However, the fibrotic pathways activated by HCM-causing sarcomere protein gene mutations are poorly defined. Because lysophosphatidic acid is a mediator of fibrosis in multiple organs and diseases, we tested the role of the lysophosphatidic acid pathway in HCM. Lysphosphatidic acid receptor 1 (LPAR1), a cell surface receptor, is required for lysophosphatidic acid mediation of fibrosis. We bred HCM mice carrying a pathogenic myosin heavy-chain variant (403+/-) with Lpar1-ablated mice to create mice carrying both genetic changes (403+/- LPAR1 -/-) and assessed development of cardiac hypertrophy and fibrosis. Compared with 403+/- LPAR1WT, 403+/- LPAR1 -/- mice developed significantly less hypertrophy and fibrosis. Single-nucleus RNA sequencing of left ventricular tissue demonstrated that Lpar1 was predominantly expressed by lymphatic endothelial cells (LECs) and cardiac fibroblasts. Lpar1 ablation reduced the population of LECs, confirmed by immunofluorescence staining of the LEC markers Lyve1 and Ccl21a and, by in situ hybridization, for Reln and Ccl21a. Lpar1 ablation also altered the distribution of fibroblast cell states. FB1 and FB2 fibroblasts decreased while FB0 and FB3 fibroblasts increased. Our findings indicate that Lpar1 is expressed predominantly by LECs and fibroblasts in the heart and is required for development of hypertrophy and fibrosis in an HCM mouse model. LPAR1 antagonism, including agents in clinical trials for other fibrotic diseases, may be beneficial for HCM.

Imaging Mass Spectrometry Reveals Tumor Metabolic Heterogeneity

Malignant tumors exhibit high degrees of genomic heterogeneity at the cellular level, leading to the view that subpopulations of tumor cells drive growth and treatment resistance. To examine the degree to which tumors also exhibit metabolic heterogeneity at the level of individual cells, we employed multi-isotope imaging mass spectrometry (MIMS) to quantify utilization of stable isotopes of glucose and glutamine along with a label for cell division. Mouse models of melanoma and malignant peripheral nerve sheath tumors (MPNSTs) exhibited striking heterogeneity of substrate utilization, evident in both proliferating and non-proliferating cells. We identified a correlation between metabolic heterogeneity, proliferation, and therapeutic resistance. Heterogeneity in metabolic substrate usage as revealed by incorporation of glucose and glutamine tracers is thus a marker for tumor proliferation. Collectively, our data demonstrate that MIMS provides a powerful tool with which to dissect metabolic functions of individual cells within the native tumor environment.

Myosin Sequestration Regulates Sarcomere Function, Cardiomyocyte Energetics, and Metabolism, Informing the Pathogenesis of Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is caused by pathogenic variants in sarcomere protein genes that evoke hypercontractility, poor relaxation, and increased energy consumption by the heart and increased patient risks for arrhythmias and heart failure. Recent studies show that pathogenic missense variants in myosin, the molecular motor of the sarcomere, are clustered in residues that participate in dynamic conformational states of sarcomere proteins. We hypothesized that these conformations are essential to adapt contractile output for energy conservation and that pathophysiology of HCM results from destabilization of these conformations.

METHODS

We assayed myosin ATP binding to define the proportion of myosins in the super relaxed state (SRX) conformation or the disordered relaxed state (DRX) conformation in healthy rodent and human hearts, at baseline and in response to reduced hemodynamic demands of hibernation or pathogenic HCM variants. To determine the relationships between myosin conformations, sarcomere function, and cell biology, we assessed contractility, relaxation, and cardiomyocyte morphology and metabolism, with and without an allosteric modulator of myosin ATPase activity. We then tested whether the positions of myosin variants of unknown clinical significance that were identified in patients with HCM, predicted functional consequences and associations with heart failure and arrhythmias.

RESULTS

Myosins undergo physiological shifts between the SRX conformation that maximizes energy conservation and the DRX conformation that enables cross-bridge formation with greater ATP consumption. Systemic hemodynamic requirements, pharmacological modulators of myosin, and pathogenic myosin missense mutations influenced the proportions of these conformations. Hibernation increased the proportion of myosins in the SRX conformation, whereas pathogenic variants destabilized these and increased the proportion of myosins in the DRX conformation, which enhanced cardiomyocyte contractility, but impaired relaxation and evoked hypertrophic remodeling with increased energetic stress. Using structural locations to stratify variants of unknown clinical significance, we showed that the variants that destabilized myosin conformations were associated with higher rates of heart failure and arrhythmias in patients with HCM.

CONCLUSIONS

Myosin conformations establish work-energy equipoise that is essential for life-long cellular homeostasis and heart function. Destabilization of myosin energy-conserving states promotes contractile abnormalities, morphological and metabolic remodeling, and adverse clinical outcomes in patients with HCM. Therapeutic restabilization corrects cellular contractile and metabolic phenotypes and may limit these adverse clinical outcomes in patients with HCM.

Hypertrophic cardiomyopathy mutations in MYBPC3 dysregulate myosin

The mechanisms by which truncating mutations in MYBPC3 (encoding cardiac myosin-binding protein C; cMyBPC) or myosin missense mutations cause hypercontractility and poor relaxation in hypertrophic cardiomyopathy (HCM) are incompletely understood. Using genetic and biochemical approaches, we explored how depletion of cMyBPC altered sarcomere function. We demonstrated that stepwise loss of cMyBPC resulted in reciprocal augmentation of myosin contractility. Direct attenuation of myosin function, via a damaging missense variant (F764L) that causes dilated cardiomyopathy (DCM), normalized the increased contractility from cMyBPC depletion. Depletion of cMyBPC also altered dynamic myosin conformations during relaxation, enhancing the myosin state that enables ATP hydrolysis and thin filament interactions while reducing the super relaxed conformation associated with energy conservation. MYK-461, a pharmacologic inhibitor of myosin ATPase, rescued relaxation deficits and restored normal contractility in mouse and human cardiomyocytes with MYBPC3 mutations. These data define dosage-dependent effects of cMyBPC on myosin that occur across the cardiac cycle as the pathophysiologic mechanisms by which MYBPC3 truncations cause HCM. Therapeutic strategies to attenuate cMyBPC activity may rescue depressed cardiac contractility in patients with DCM, whereas inhibiting myosin by MYK-461 should benefit the substantial proportion of patients with HCM with MYBPC3 mutations.

Targeting nuclear receptor NR4A1-dependent adipocyte progenitor quiescence promotes metabolic adaptation to obesity

Adipocyte turnover in adulthood is low, suggesting that the cellular source of new adipocytes, the adipocyte progenitor (AP), resides in a state of relative quiescence. Yet the core transcriptional regulatory circuitry (CRC) responsible for establishing a quiescent state and the physiological significance of AP quiescence are incompletely understood. Here, we integrate transcriptomic data with maps of accessible chromatin in primary APs, implicating the orphan nuclear receptor NR4A1 in AP cell-state regulation. NR4A1 gain and loss of function in APs ex vivo decreased and enhanced adipogenesis, respectively. Adipose tissue of Nr4a1-/- mice demonstrated higher proliferative and adipogenic capacity compared with that of WT mice. Transplantation of Nr4a1-/- APs into the subcutaneous adipose tissue of WT obese recipients improved metrics of glucose homeostasis relative to administration of WT APs. Collectively, these data identify NR4A1 as a previously unrecognized constitutive regulator of AP quiescence and suggest that augmentation of adipose tissue plasticity may attenuate negative metabolic sequelae of obesity.

The circulating metabolome of human starvation

The human adaptive starvation response allows for survival during long-term caloric deprivation. Whether the physiology of starvation is adaptive or maladaptive is context dependent: activation of pathways by caloric restriction may promote longevity, yet in the context of caloric excess, the same pathways may contribute to obesity. Here, we performed plasma metabolite profiling of longitudinally collected samples during a 10-day, 0-calorie fast in humans. We identify classical milestones in adaptive starvation, including the early consumption of gluconeogenic amino acids and the subsequent surge in plasma nonesterified fatty acids that marks the shift from carbohydrate to lipid metabolism, and demonstrate findings, including (a) the preferential release of unsaturated fatty acids and an associated shift in plasma lipid species with high degrees of unsaturation and (b) evidence that acute, starvation-mediated hypoleptinemia may be a driver of the transition from glucose to lipid metabolism in humans.

Abstract 571: MYBPC3 Mutations Cause Hypertrophic Cardiomyopathy by Dysregulating Myosin: Implications for Therapy

The mechanisms by which truncating mutations in MYBPC3 (encoding cardiac myosin binding protein-C; cMyBPC) or myosin missense mutations cause hyper-contractility and poor relaxation in hypertrophic cardiomyopathy (HCM) are incompletely understood. Using genetic and biochemical approaches we explored how depletion of cMyBPC altered sarcomere function. We demonstrate that stepwise loss of cMyBPC resulted in reciprocal augmentation of myosin contractility. Direct attenuation of myosin function, via a damaging missense variant (F764L) that causes dilated cardiomyopathy (DCM) normalized the increased contractility from cMyBPC depletion. Depletion of cMyBPC also altered dynamic myosin conformations during relaxation - enhancing the myosin state that enables ATP hydrolysis and thin filament interactions while reducing the super relaxed conformation associated with energy conservation. MYK-461, a pharmacologic inhibitor of myosin ATPase, rescued relaxation deficits and restored normal contractility in mouse and human cardiomyocytes with MYBPC3 mutations. These data define dosage-dependent effects of cMyBPC on myosin that occur across all phases of the cardiac cycle as the pathophysiologic mechanisms by which MYBPC3 truncations cause HCM. Therapeutic strategies to attenuate cMyBPC activity may rescue depressed cardiac contractility in DCM patients, while inhibiting myosin by MYK-461 should benefit the substantial proportion of HCM patients with MYBPC3 mutations.

Imaging mass spectrometry demonstrates age-related decline in human adipose plasticity

Quantification of stable isotope tracers has revealed the dynamic state of living tissues. A new form of imaging mass spectrometry quantifies isotope ratios in domains much smaller than a cubic micron, enabling measurement of cell turnover and metabolism with stable isotope tracers at the single-cell level with a methodology we refer to as multi-isotope imaging mass spectrometry. In a first-in-human study, we utilize stable isotope tracers of DNA synthesis and de novo lipogenesis to prospectively measure cell birth and adipocyte lipid turnover. In a study of healthy adults, we elucidate an age-dependent decline in new adipocyte generation and adipocyte lipid turnover. A linear regression model suggests that the aging effect could be mediated by a decline in insulin-like growth factor-1 (IGF-1). This study therefore establishes a method for measurement of cell turnover and metabolism in humans with subcellular resolution while implicating the growth hormone/IGF-1 axis in adipose tissue aging.

FGF21 and the late adaptive response to starvation in humans

In mice, FGF21 is rapidly induced by fasting, mediates critical aspects of the adaptive starvation response, and displays a number of positive metabolic properties when administered pharmacologically. In humans, however, fasting does not consistently increase FGF21, suggesting a possible evolutionary divergence in FGF21 function. Moreover, many key aspects of FGF21 function in mice have been identified in the context of transgenic overexpression or administration of supraphysiologic doses, rather than in a physiologic setting. Here, we explored the dynamics and function of FGF21 in human volunteers during a 10-day fast. Unlike mice, which show an increase in circulating FGF21 after only 6 hours, human subjects did not have a notable surge in FGF21 until 7 to 10 days of fasting. Moreover, we determined that FGF21 induction was associated with decreased thermogenesis and adiponectin, an observation that directly contrasts with previous reports based on supraphysiologic dosing. Additionally, FGF21 levels increased after ketone induction, demonstrating that endogenous FGF21 does not drive starvation-mediated ketogenesis in humans. Instead, a longitudinal analysis of biologically relevant variables identified serum transaminases--markers of tissue breakdown--as predictors of FGF21. These data establish FGF21 as a fasting-induced hormone in humans and indicate that FGF21 contributes to the late stages of adaptive starvation, when it may regulate the utilization of fuel derived from tissue breakdown.

Loss of white adipose hyperplastic potential is associated with enhanced susceptibility to insulin resistance

Fat mass expansion occurs by adipocyte hypertrophy or recruitment of differentiating adipocyte progenitors, the relative balance of which may impact systemic metabolism. We measured adipogenesis in murine subcutaneous (sWAT) and visceral white adipose tissue (vWAT) using stable isotope methodology and then modeled adipocyte turnover. Birth and death rates were similar within depots; however, turnover was higher in vWAT relative to sWAT. In juvenile mice, obesity increased adipogenesis, but in adults, this was only seen in vWAT after prolonged high-fat feeding. Statistical modeling suggests differentiation of adipocyte progenitors without an accompanying self-renewing division step may partially explain the age-dependent decline in hyperplastic potential. Additional metabolic interrogation of obese mice demonstrated an association between adipocyte turnover and insulin sensitivity. These data therefore identify adipocyte hypertrophy as the dominant mechanism of adult fat mass expansion and support the paradoxical concept that metabolic disease ensues due to a failure of adipose tissue plasticity.

Heat shock protein expression is highly sensitive to ischemia-reperfusion injury in rat kidneys

Renal injury is known to trigger upregulation of many intracellular signal proteins, but those most sensitive in responding to renal injury remain debatable. We used gene microarray analysis to compare gene expression in rat kidneys subjected to early ischemia-reperfusion injury (30 min of renal ischemia and 3 hr of reperfusion) with non-ischemic kidneys as controls. Among 31,100 genes analyzed, microarray analysis revealed 21 genes with >3-fold increase in expression in ischemic kidneys compared to control non-ischemic kidneys. These upregulated genes included heat shock protein 70 (43-fold), heat shock protein 27 (12-fold), heme oxygenase-1 (10-fold), kidney injury molecule-1 (8-fold), and several subtypes of S100 calcium-binding proteins (3.1- to 7.5-fold). Following a prolonged reperfusion period (48 hr) after 30 min of ischemia, acute tubular necrosis was obvious in the S3 segment of proximal tubules of ischemic kidneys. Injured proximal tubules showed upregulated expression of heat shock protein 70 by immunohistochemistry and by Western blotting. These data suggest that heat shock proteins (eg, heat shock protein 70, heat shock protein 27, and heme oxygenase-1) are crucial for renal cell response to ischemic injury and that heat shock protein 70 is a highly sensitive intracellular marker of ischemia-reperfusion injury.

C4d positivity is often associated with acute cellular rejection in renal transplant biopsies following Campath-1H (Alemtuzumab) induction

Peritubular capillary C4d positivity, a marker for antibody-mediated rejection, is observed in approximately 20-50% of indicated renal transplant biopsies and in just 2% of unremarkable protocol biopsies. However, C4d staining has not been evaluated in protocol renal biopsies from patients with Campath-1H induction treatment, and the association between various types of inflammatory cells and acute antibody-mediated rejection is unclear. This study investigated the rates of C4d positivity in unremarkable protocol renal biopsies, biopsies with acute tubular necrosis (ATN), and biopsies with acute cellular rejection (ACR), all following Campath-1H treatment and post-operative immunosuppression. There was low positivity of C4d staining in both the protocol and ATN groups, but the ACR group had a 47.2% rate of positivity (combining focal and diffuse positive cases). Since Campath-1H treatment caused significant depletion of circulating lymphocytes but not circulating monocytes in renal recipients, this study also investigated the role of monocytes in humoral rejection. In ACR cases, CD68 positive monocytes were composed of 59.4 +/- 4.69% inflammatory cells, which was significantly higher than CD3 positive lymphocytes (38.9 +/- 4.4%). Co-localization of positive C4d staining in endothelium and marginating CD68 positive monocytes was illustrated by double staining. Our data indicate that acute antibody-mediated rejection occurs much more frequently in renal transplants with ACR. Moreover, the high percentage of monocytes observed in ACR cases (due to monocytes being less sensitive to Campath-1H depletion) suggests that monocytes are involved in antibody-mediated rejection.

Identification of functional domains in sarcoglycans essential for their interaction and plasma membrane targeting

Mutations in sarcoglycans have been reported to cause autosomal-recessive limb-girdle muscular dystrophies. In skeletal and cardiac muscle, sarcoglycans are assembled into a complex on the sarcolemma from four subunits (alpha, beta, gamma, delta). In this report, we present a detailed structural analysis of sarcoglycans using deletion study, limited proteolysis and co-immunoprecipitation. Our results indicate that the extracellular regions of sarcoglycans consist of distinctive functional domains connected by proteinase K-sensitive sites. The N-terminal half domains are required for sarcoglycan interaction. The C-terminal half domains of beta-, gamma- and delta-sarcoglycan consist of a cysteine-rich motif and a previously unrecognized conserved sequence, both of which are essential for plasma membrane localization. Using a heterologous expression system, we demonstrate that missense sarcoglycan mutations affect sarcoglycan complex assembly and/or localization to the cell surface. Our data suggest that the formation of a stable complex is necessary but not sufficient for plasma membrane targeting. Finally, we provide evidence that the beta/delta-sarcoglycan core can associate with the C-terminus of dystrophin. Our results therefore generate important information on the structure of the sarcoglycan complex and the molecular mechanisms underlying the effects of various sarcoglycan mutations in muscular dystrophies.

Morphoproteomic and molecular concomitants of an overexpressed and activated mTOR pathway in renal cell carcinomas

CCI-779 (temsirolimus), an ester of rapamycin and an inhibitor of the mammalian target of rapamycin (mTOR), is currently in phase II trials for treatment of patients with solid cancers. The mTOR functions as a checkpoint for cell proliferation, with upstream Akt and downstream p70S6K serving as its most important mediators. The aim of this study was to evaluate the expression and activation of the Akt-mTOR-p70S6K pathway in renal cell carcinoma (RCC), seeking to strengthen the rationale for targeted therapy of RCC using rapamycin or a rapamycin analogue. Tissue microarray sections containing 128 primary RCCs, 22 metastatic RCCs, and 24 non-neoplastic (normal) kidneys (NK) were immunostained with monoclonal antibodies to phosphorylated (p)-Akt (Ser473), p-mTOR (Ser2448), and p-p70S6K (Thr389). Western blotting was performed on 3 cases of clear cell RCC (CRCC) and the corresponding non-neoplastic (normal) renal tissues using the same antibodies. The immunostain scoring system included: (a) location; (b) distribution; and (c) intensity. The normal kidneys provided baseline scores for comparison. Expression of p-Akt, p-mTOR, and p-p70S6K was seen in 100% (n = 24) of NKs and nearly 100% (n = 150) of both primary and metastatic RCCs. The p-p70S6K was located in the nucleus in both NKs and RCCs. The p-Akt was observed in the nucleus and cytoplasm of NKs and in the nucleus and cytoplasm/ membrane (plasmalemma) of RCCs. The p-mTOR was identified in the membrane of NKs and the membrane/nucleus of RCCs. The levels of expression of p-p70S6K, p-mTOR, and p-Akt were significantly higher in RCC than in NK in the overall pattern (intensity and distribution, p <0.05). Western blotting also showed higher expression of p-p70S6K, p-mTOR, and p-Akt in RCCs compared to the corresponding normal kidney tissues (p <0.05). These findings indicate that correlative over-expression and activation of p-Akt, p-mTOR, and p-p70S6K are commonly observed in RCCs. After considering these findings in the context of other established protein circuitries and pathways in RCC, we propose therapeutic approaches that incorporate rapamycin-like agents and other small molecule inhibitors in a combinatorial fashion in future clinical trials for RCC.

Morphoproteomic and pharmacoproteomic rationale for mTOR effectors as therapeutic targets in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) has a relatively high mortality rate and poor prognosis. Recently, we showed that overexpression of phosphorylated (p) nuclear factor-kappaB (NF-kappaB) in squamous cell carcinoma of the tonsil (SCCT) and high grade dysplasia is associated with a poor prognosis. Because the mammalian target of the rapamycin (mTOR) pathway contributes to the activation of NF-kappaB through immunophilin/mTOR signaling, we investigated: (a) the immunohistochemical expression and state of activation and potential clinical significance of components of the mTOR signal transduction pathway in SCCT patients (morphoproteomics); and (b) the inhibitory effects of rapamycin on the growth and state of activation of mTOR in 2 HNSCC cell lines (pharmacoproteomics). Archival biopsy materials from 39 patients with SCCT were studied by immunohistochemistry for the expression of p-mTOR (Ser 2448), and p-p70S6K (Thr 389), and/or cyclin D1. Results for SCCT were compared with adjacent non-neoplastic epithelium, when present, and with normal tonsillar epithelium from approximately age-matched controls; clinical outcomes were also assessed. SCCT showed mTOR (Ser 2448) expression in 93% (30/32 cases) with 2+ or 3+ plasmalemmal and/or cytoplasmic intensity in 84% vs 42% in surface epithelium from normal tonsils (p <0.001). The mean combined expression score (signal intensity x percentage of positive cells) for p-p70S6K was significantly greater in the SCCT group vs adjacent non-neoplastic squamous epithelium and normal tonsillar epithelium of the control group (p <0.05). A relationship existed between higher p-p70S6K expression levels in the non-neoplastic squamous epithelium adjacent to the SCCT and increased risk of death from disease (hazard ratio = 7.9; 95% confidence interval (CI) = 2.1 to 29.9; p = 0.002). There was also a relationship between nuclear expression of cyclin D1 in SCCT and shortened recurrence-free survival (p = 0.015). Two human HNSCC cell lines, SCC-15 and FaDu, were incubated with and without rapamycin to assess its impact on growth and on the expression of p-mTOR. Rapamycin in a dose-dependent fashion inhibited growth more in SCC-15, which correlated with a greater reduction in constitutively activated p-mTOR (Ser 2448) as shown by Western blotting. In conclusion, these morphoproteomic and pharmacoproteomic data collectively provide a rationale for selecting mTOR effectors as therapeutic targets in HNSCC.

Overexpression of phosphorylated nuclear factor-kappa B in tonsillar squamous cell carcinoma and high-grade dysplasia is associated with poor prognosis

Intracellular signals along the epidermal growth factor receptor (EGFR)-Akt-nuclear factor-kappa B (NF-kappaB) pathway have been associated with carcinogenesis in various malignant neoplasms. This investigation was to evaluate the expression of EGFR, phosphorylated(p)-Akt and p-NF-kappaB and correlate them with clinical outcomes in patients with squamous cell carcinoma of the tonsil. A total of 45 patients with squamous cell carcinoma of the tonsil were studied by immunohistochemistry to evaluate the expression levels of EGFR, p-Akt and p-NF-kappaB. Results for squamous cell carcinoma of the tonsil were compared with those for associated high-grade dysplasia and adjacent normal appearing epithelium, when present. In addition, tonsillar epithelium from non-neoplastic specimens of age-matched patients also was stained for the same markers. High-grade dysplasia and squamous cell carcinoma of the tonsil demonstrated a similar pattern of expression, which differed from the pattern seen in the adjacent normal epithelium and tonsillar epithelium from normal controls (an overexpression for each of these three protein analytes in high-grade dysplasia and squamous cell carcinoma of the tonsil as demonstrated by immunohistochemistry). When markers from squamous cell carcinoma of the tonsil were correlated with survival status, only increasing levels of p-NF-kappaB immunoreactivity (a relative overexpression) were statistically significant predictors of poor survival. No markers in squamous cell carcinoma of the tonsil were significantly related to rate of recurrence. When analyzing marker scores from tissue with high-grade dysplasia, relative overexpressions of both p-Akt and p-NF-kappaB were significantly related to poor survival. Additionally, increasing levels of p-NF-kappaB immunopositivity from tissue with high-grade dysplasia were also significantly related to rate of recurrence. In summary, p-NF-kappaB, overexpressed in high-grade dysplasia and squamous cell carcinoma of the tonsil, is associated with worse prognosis in terms of high recurrence and poor survival, respectively. This significant finding in patients with squamous cell carcinoma of the tonsil, in combination with previous animal and in vitro studies, suggests that p-NF-kappaB represents a potential therapeutic target in head and neck squamous cell carcinoma.

Acute cellular rejection predominated by monocytes is a severe form of rejection in human renal recipients with or without Campath-1H (alemtuzumab) induction therapy

Campath-1H has been used successfully for induction and has resulted in a low rate of acute cellular rejection (ACR) in renal transplantation in combination with various postoperative immunosuppression regimens. This study was undertaken to investigate the extent of monocyte involvement in ACR, with or without Campath-1H induction. We found that monocytes represented the majority of inflammatory cells in grades Ib or higher ACR, but not with Ia type of ACR, regardless of the status of Campath-1H induction. Cases of ACR, following Campath-1H induction, appear to demonstrate a 'pure form' of monocytic ACR, whereas monocytes were mixed with many other types of inflammatory cells in the cases of ACR in the absence of Campath-1H induction. In addition with Campath-1H induction, the cases of monocyte-predominant ACR were found to uniformly exhibit a good response to corticosteroid treatment. We conclude that monocyte-predominate ACR may represent a severe form of rejection, with or without Campath-1H treatment.

Intracellular inhibitory effects of Velcade correlate with morphoproteomic expression of phosphorylated-nuclear factor-kappaB and p53 in breast cancer cell lines

Velcade, a proteasome inhibitor, has been shown to inhibit DNA binding activity of nuclear factor-kappaB (NF-kappaB) and to stabilize p53 in vitro. But its impact, in the context of activated (phosphorylated and translocated) NF-kappaB and the expression of p53, has not been studied in breast cancer. It would be desirable to determine whether or not the immunohistochemical (IHC) expressions of activated NF-kappaB and of p53 can predict the effects of Velcade in viable tumor cells. To answer these questions, we selected 3 breast cancer cell lines (SKBR-3, MDA-175, and MDA-231), which are negative for hormonal receptors, but differ in HER-2/neu expression (strong, mild, and minimal, respectively). The 3 cell lines showed different expressions of phosphorylated (p)- NF-kappaB and p53, as evaluated using immunohistochemistry with visual quantification by brightfield microscopy. After being treated with Velcade for 2 days, MDA-231 cells showed markedly reduced proliferation, followed by SKBR-3 cells, and then by MDA-175 cells. There was strong correlation between the nuclear expression of either p-NF-kappaB or p53 and the inhibitory rate of Velcade in the 3 cell lines (r = 0.987 and 0.807, respectively). Western blotting showed an increase in inhibitor-kappaB (I-kappaB) expression in nuclei of MDA-231 and SKBR-3 cells, but not in MDA-175 cells, following exposure to Velcade. Velcade treatment resulted in cleaved caspase-3 expression in MDA-231 cells and in the overexpression of p53 and p21WAF1 in all 3 cell lines, as evaluated using Western blotting. In summary, morphoproteomic analysis of p-NF-kappaB and p53 can be correlated with the inhibitory effect of Velcade in vitro. We propose that this proliferative inhibition is variably associated with blocking p-NF-kappaB function by upregulation of nuclear I-kappaB, stabilization of p53, and induction of p21WAF1.

Nuclear factor-kappaB pathway as a therapeutic target in head and neck squamous cell carcinoma: pharmaceutical and molecular validation in human cell lines using Velcade and siRNA/NF-kappaB

BACKGROUND

Nuclear factor-kappaB (NF-kappaB) is synthesized in the cytoplasm, complexed with its inhibitor, I-kappaB, and NF-kappaB is released in an activated (phosphorylated) form following phosphorylation of I-kappaB and proteasomal degradation of the NF-kappaB.p-kappaB complex. The free p-NF-kappaB can then be translocated to the nucleus where it effects transcriptional activation of genes leading to the synthesis of proteins that are generally pro-growth and anti-apoptosis.

OBJECTIVE

To gain insight into the role of the NF-kappaB pathway in head and neck squamous cell carcinoma (HNSCC), we selected two HNSCC cell lines, SCC-15 of lingual origin and FaDu of pharyngeal origin, with constitutively activated (phosphorylated) NF-kappaB. We assessed the impact of interrupting the NF-kappaB pathway at the level of proteasomal degradation using Velcade (bortezomib), a proteasome inhibitor, and at the pretranslational level in the synthesis of NF-kappaB using a small interfering RNA (siRNA).

RESULTS

Velcade produced a dose-dependent inhibition of cell growth in both cell lines. At 30 nM, Velcade inhibited cell growth in the SCC-15 cell line by 40%. In both cell lines, Velcade induced nuclear overexpression of p21(WAF1), an inhibitor of G1 cell cycle progression, which appeared to be independent of p53 expression. Addition of siRNA augmented the inhibitory effects of Velcade in FaDu cells; siRNA/NF-kappaB alone led to a 48% decline in basal expression of NF-kappaB protein levels and effected a 25% inhibition of cell growth. In the presence of Velcade (30 nM), siRNA/NF-kappaB increased growth inhibition from 43 to 65%.

CONCLUSIONS

The mechanisms involved in growth inhibitory effects of Velcade on HNSCC cell lines include the NF-kappaB pathway, suggesting the possible therapeutic use of Velcade or other NF-kappaB pathway inhibitors (eg, curcumin). The data also suggest that combining siRNA/NF-kappaB with Velcade might achieve greater reduction in the growth of HNSCC in patients with constitutively activated NF-kappaB.

Preinduced molecular chaperones in the endoplasmic reticulum protect cardiomyocytes from lethal injury

Although molecular chaperones in the endoplasmic reticulum (ER) are known to be involved in folding and assembly of glycosylated proteins, it is unclear whether preinduced ER chaperones can protect cardiomyocytes from lethal injury. In this study we used tunicamycin, an inhibitor of N-linked glycosylation in the ER, to preinduce ER chaperones in H9c2 cardiomyocytes and we tested the cytoprotective role of preinduced ER chaperones in the cardiomyocytes. Expression of GRP78 at both protein and mRNA levels was markedly increased in cardiomyocytes pretreated with tunicamycin, when compared to non-treatment controls. Following prolonged ATP depletion or oxidative stress, which was used to simulate cardiac ischemia and reperfusion injury, respectively, the release of lactate dehydrogenase (LDH) from tunicamycin-pretreated cardiomyocytes was significantly lower than from non-pretreated cardiomycocytes. Tunicamycin-pretreated cardiomyocytes showed significantly higher Ca2+ release into cytoplasm than controls when treated with both caffeine and thapsigargin, indicating higher storage of Ca2+ in the ER. After oxidative stress, cytosolic Ca2+ levels were maintained relatively stable in tunicamycin-pretreated cardiomyocytes, when compared to control cardiomyocytes. These observations suggest that preinduced ER chaperones protect cardiomyocytes from lethal injury, at least in part, by preventing an increase in cytosolic Ca2+.

Morphoproteomic and pharmacoproteomic correlates in hormone-receptor-negative breast carcinoma cell lines

The aim of this study was to elucidate protein circuitry in breast cancer based on the profiling of hormone-receptor-negative breast carcinomas using morphoproteomic and pharmacoproteomic techniques. Three human breast carcinoma cell lines (SKBR-3, MDA-175, MDA-231) were reacted by immunohistochemical (IHC) procedures to detect several categories of protein analytes. Immunoreactivities and cell compartmentalizations were scored from 0 to 3+ positivity using bright-field microscopy. An automated cellular imaging system (ACIS) was used to obtain a final combined score of staining intensity and positive cells in the IHC reactions, to enable comparisons with the visual scores and the rates of inhibition by pharmaceutical agents. FDA-approved inhibitors that target the protein circuitry were added to the cultures for 2-4 days. Proliferation assays were conducted, and in vitro inhibition rates were calculated as (control - treated)/control. Western blot analyses of whole cell lysates assessed the effects of the pharmaceutical agents on selected aspects of protein circuitry. Good to excellent correlation was observed between visual scores and ACIS scores (r values from 0.732 to 0.996 in 10 of 11 trials). Gleevec produced growth inhibition that correlated with the composite expressions of the platelet-derived growth factor (PDGF) family of ligands and receptors; captopril inhibited only MDA-175, consistent with its unique expression of plasmalemmal angiotensin-converting enzyme (ACE); and interferon (IFN)-alpha effected growth inhibition in accordance with the degree of conventional (c) protein kinase C (PKC)-alpha and phosphorylated (p)-PKCalpha/betaII expressions. Western blot analyses revealed correlative changes of several intracellular signals following incubation with these inhibitors. This study shows (a) a close association between the immunohistochemical expression of signal transduction markers and in vitro inhibition by pharmaceutical agents, and (b) correlations between the sites of action of the pharmaceutical agents and the downstream expression of proteins in hormone-receptor-negative breast cancer cell lines. Such morphoproteomic and pharmacoproteomic profiling of individual tumors may enable the pathologist and oncologist to design antitumor therapy that is customized for an individual patient.

Pamidronate resistance and associated low ras levels in breast cancer cells: a role for combinatorial therapy

To identify markers sensitive to inhibitors of the farnesylation pathway, we used 3 breast cancer cell lines (SKBR-3, MDA-175, and MDA-231) to evaluate the in vitro effects of pamidronate, an inhibitor of farnesyl diphosphate synthase. In response to pamidronate, there was significant inhibition of cell proliferation in MDA-231 and SKBR-3 cells, compared to MDA-175 cells. This correlated with their respective basal levels of N-ras and H-ras. N-ras and H-ras protein levels were both reduced in MDA-231 cells, and to lesser extent in SKBR-3 cells, following exposure to pamidronate, whereas these markers were not altered in MDA-175 cells. Combinatorial therapy with pamidronate and Gleevec, an inhibitor of several tyrosine kinases; Velcade, a proteasome inhibitor; or rapamycin, an inhibitor of the mammalian target of rapamycin (m-TOR) all showed additive effects in causing proliferative inhibition in MDA-175 cells. In summary, resistance to pamidronate may result from low levels of GTPase-activating proteins, such as N-ras and H-ras, in tumor cells. Combinatorial therapies directed against other signaling pathways, not dependent upon ras, may be required to overcome such resistance.

Rrn3 becomes inactivated in the process of ribosomal DNA transcription

The human homologue of yeast Rrn3, a 72-kDa protein, is essential for ribosomal DNA (rDNA) transcription. Although the importance of Rrn3 function in rDNA transcription is well established, its mechanism of action has not been determined. It has been suggested that the phosphorylation of either yeast RNA polymerase I or mammalian Rrn3 regulates the formation of RNA polymerase I.Rrn3 complexes that can interact with the committed template. These and other reported differences would have implications with respect to the mechanism by which Rrn3 functions in transcription. For example, in the yeast rDNA transcription system, Rrn3 might function catalytically, but in the mammalian system it might function stoichiometrically. Thus, we examined the question as to whether Rrn3 functions catalytically or stoichiometrically. We report that mammalian Rrn3 becomes the limiting factor as transcription reactions proceed. Moreover, we demonstrate that Rrn3 is inactivated during the transcription reactions. For example, Rrn3 isolated from a reaction that had undergone transcription cannot activate transcription in a subsequent reaction. We also show that this inactivated Rrn3 not only dissociates from RNA polymerase I, but is not capable of forming a stable complex with RNA polymerase I. Our results indicate that Rrn3 functions stoichiometrically in rDNA transcription and that its ability to associate with RNA polymerase I is lost upon transcription.

Overexpression of Na+/Ca2+ exchanger alters contractility and SR Ca2+ content in adult rat myocytes

The functional consequences of overexpression of rat heart Na+/Ca2+ exchanger (NCX1) were investigated in adult rat myocytes in primary culture. When maintained under continued electrical field stimulation conditions, cultured adult rat myocytes retained normal contractile function compared with freshly isolated myocytes for at least 48 h. Infection of myocytes by adenovirus expressing green fluorescent protein (GFP) resulted in >95% infection as ascertained by GFP fluorescence, but contraction amplitude at 6-, 24-, and 48-h postinfection was not affected. When they were examined 48 h after infection, myocytes infected by adenovirus expressing both GFP and NCX1 had similar cell sizes but exhibited significantly altered contraction amplitudes and intracellular Ca2+ concentration ([Ca2+]i) transients, and lower resting and diastolic [Ca2+]i when compared with myocytes infected by the adenovirus expressing GFP alone. The effects of NCX1 overexpression on sarcoplasmic reticulum (SR) Ca2+ content depended on extracellular Ca2+ concentration ([Ca2+]o), with a decrease at low [Ca2+]o and an increase at high [Ca2+]o. The half-times for [Ca2+]i transient decline were similar, suggesting little to no changes in SR Ca2+-ATPase activity. Western blots demonstrated a significant (P < or = 0.02) threefold increase in NCX1 but no changes in SR Ca2+-ATPase and calsequestrin abundance in myocytes 48 h after infection by adenovirus expressing both GFP and NCX1 compared with those infected by adenovirus expressing GFP alone. We conclude that overexpression of NCX1 in adult rat myocytes incubated at high [Ca2+]o resulted in enhanced Ca2+ influx via reverse NCX1 function, as evidenced by greater SR Ca2+ content, larger twitch, and [Ca2+]i transient amplitudes. Forward NCX1 function was also increased, as indicated by lower resting and diastolic [Ca2+]i.

Rb and p130 regulate RNA polymerase I transcription: Rb disrupts the interaction between UBF and SL-1

We have previously demonstrated that the protein encoded by the retinoblastoma susceptibility gene (Rb) functions as a regulator of transcription by RNA polymerase I (rDNA transcription) by inhibiting UBF-mediated transcription. In the present study, we have examined the mechanism by which Rb represses UBF-dependent rDNA transcription and determined if other Rb-like proteins have similar effects. We demonstrate that authentic or recombinant UBF and Rb interact directly and this requires a functional A/B pocket. DNase footprinting and band-shift assays demonstrated that the interaction between Rb and UBF does not inhibit the binding of UBF to DNA. However, the formation of an UBF/Rb complex does block the interaction of UBF with SL-1, as indicated by using the 48 kDa subunit as a marker for SL-1. Additional evidence is presented that another pocket protein, p130 but not p107, can be found in a complex with UBF. Interestingly, the cellular content of p130 inversely correlated with the rate of rDNA transcription in two physiological systems, and overexpression of p130 inhibited rDNA transcription. These results suggest that p130 may regulate rDNA transcription in a similar manner to Rb.

The neoplastic transformation of SCID cells by radiation

Severe combined immunodeficiency (SCID) cells are hypersensitive to killing by ionizing radiation because of deregulation of DNA-dependent protein kinase (DNA-PK) and a concomitant deficiency in the repair of DNA double-strand breaks. The effect of this condition on the neoplastic transformation of SCID fibroblasts, designated SCID 3T1, has been investigated. The spontaneous transformation rate was approximately 2 x 10(-5) at early passages and increased up to approximately 7 x l0(-3) at later passages. The radiation survival curves of transformed cells had thresholds and therefore appeared to be qualitatively similar to the survival curves of C3H 10T(1/2) mouse fibroblast cells, but the initial slopes were steeper. In contrast, per unit dose, SCID cells were more sensitive to transformation than 10T(1/2) cells. Eight transformed clones were tested for tumorigenicity, and all produced fibrosarcomas in athymic nude mice. Properties associated with the tumor suppressor Trp53 (formerly known as p53) were examined in three of the clones. In these clones, although Trp53 protein was overexpressed, a lower expression of Cdkn1a (formerly known as p21, Cip1) protein was observed compared to parental cells. The expression of Trp53 and Cdkn1a and the G(1)-phase arrest (one set of data on G(1)-phase delay is included as an example) was not induced by ionizing radiation in these transformed clones; each clone carried a point mutation in Trp53. This suggests that the deficiency in the repair of DNA double-strand breaks increased the tumorigenicity and the genomic instability of transformed SCID cells.

p53 gene mutations in neoplastic transformation of C3H 10T1/2 and severe combined immunodeficiency fibroblasts

The relevance of p53 mutations to the neoplastic malignant transformation of rodent fibroblasts by genotoxic physical and chemical agents is not clear. In the present study, we investigated p53 mutations (in exons 5-8) in non-transformed and neoplastically transformed C3H 10T1/2 and severe combined immunodeficiency (SCID) cells. No p53 mutations were detected in 15 neoplastically transformed (two spontaneous, one 3-methylcholanthrene-induced, seven gamma-ray-induced and five 'hot particle'-induced) and two non-transformed 10T1/2 cells. Wild-type p53 gene was also detected in all non-transformed (immortalized) SCID cell lines analyzed (four lines) whereas all three neoplastically transformed (two spontaneous, one gamma-ray-induced) cell lines displayed missense mutations in the p53 gene. These mutations were all transitions: A > G in codon 123, G > A in codon 152, and C > T in codon 238. We conclude that mutation in the p53 gene appears to be an infrequent event in 10T1/2 cells regardless of the transforming agent, but a frequent event in the neoplastic transformation of immortalized SCID cells. Non-transformed SCID cells are deficient in repair of DNA double-strand breaks, and neoplastically transformed cells are assumed to be deficient as well.