Abstract P207: BBP-398, a potent, small molecule inhibitor of SHP2, enhances the response of established NSCLC xenografts to KRASG12C and mutEGFR inhibitors

Src homology 2 domain-containing phosphatase (SHP2), a ubiquitously expressed non-receptor tyrosine phosphatase, plays a critical role in the regulation of the MAPK signaling pathway and cellular proliferation. Activating mutations in SHP2 are associated with the development of multiple malignancies including leukemia, lung cancer and neuroblastoma. In addition, SHP2 promotes the conversion of oncogenic KRAS to its active GTP-bound state and it’s inhibition can enhance efficacy of GDP-KRASG12C inhibitors as well as other MAPK pathway inhibitors (RAF, MEK and ERK) which have suboptimal clinical efficacy as single agents. As a result, inhibition of SHP2 through genetic manipulation or pharmacological means has been shown to suppress tumor growth and presents an attractive potential avenue for the treatment of malignancies as monotherapy or in combination with other MAPK/PI3K inhibitors. Here we describe BBP-398, a potent, orally bioavailable allosteric small molecule inhibitor of SHP2. BBP-398 displays high selectivity against other phosphatases, kinases, GPCRs, transporters and hERG. Predicted human PK properties show good oral bioavailability with half-life of ~12-16 hours enabling continuous daily dosing and optimal therapeutic index in combination with other targeted therapeutics. In cellular assays, BBP-398 demonstrates potent pERK/DUSP6 inhibition and loss of viability across a panel of cell lines with active MAPK signaling, such as mutant EGFR and KRASG12C. In vivo, BBP-398 strongly suppresses RAS-ERK signaling in RTK- or RAS-driven xenografts. In the EGFR-dependent non-small cell lung cancer (NSCLC) HCC827 and esophageal squamous cell carcinoma KYSE-520 xenograft models, BBP-398 drives dose dependent efficacy consistent with the level of target inhibition. Detailed analysis of tumor response shows that efficacy is driven by maintaining better than 50% inhibition of pERK for most of the dosing interval. In addition to its strong single agent activity, BBP-398 also leads to enhanced efficacy in vitro and in vivo when used in combination with targeted therapeutics against driver MAPK genetic alterations, such as KRAS, EGFR or MET. Combination targeting, such as with the GDP-KRASG12C inhibitor sotorasib in the NSCLC NCI-H358 xenograft model, or with the mutant EGFR inhibitor osimertinib in the HCC827 erlotinib resistant (ER) xenograft model, drives strong suppression of MAPK activity and results in tumor regressions. Collectively, these findings highlight that SHP2 inhibition is a promising molecular therapeutic strategy in cancer which can potentially strongly suppress tumor growth as a single agent or in combination with other MAPK pathway inhibitors. Given its preclinical properties and projected favorable clinical pharmacokinetic profile, BBP-398 is currently being evaluated in a Phase 1/1b trial in patients with advanced solid tumors (NCT04528836).

Citation Format: James P. Stice, Sofia Donovan, Yuting Sun, Nancy Kohl, Barbara Czako, Faika Mseeh, Paul Leonard, Anna Wade, Justin Lim, Phil Jones, Eli Wallace, Kerstin Sinkevicius, Pedro Beltran. BBP-398, a potent, small molecule inhibitor of SHP2, enhances the response of established NSCLC xenografts to KRASG12C and mutEGFR inhibitors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P207.

Validation of histone deacetylase 3 as a therapeutic target in castration-resistant prostate cancer

BACKGROUND

Whereas the androgen receptor (AR) signaling axis remains a therapeutic target in castration-resistant prostate cancer (CRPC), the emergence of AR mutations and splice variants as mechanisms underlying resistance to contemporary inhibitors of this pathway highlights the need for new therapeutic approaches to target this disease. Of significance in this regard is the considerable preclinical data, indicating that histone deacetylase (HDAC) inhibitors may have utility in the treatment of CRPC. However, the results of clinical studies using HDAC inhibitors (directed against HDAC1, 2, 3, and 8) in CRPC are equivocal, a result that some have attributed to their ability to induce an epithelial to mesenchymal transition (EMT) and neuroendocrine differentiation. We posited that it might be possible to uncouple the beneficial effects of HDAC inhibitors on AR signaling from their undesired activities by targeting specific HDACs as opposed to using the pan-inhibitor strategy that has been employed to date.

METHODS

The relative abilities of pan- and selective-Class I HDAC inhibitors to attenuate AR-mediated target gene expression and proliferation were assessed in several prostate cancer cell lines. Small interfering RNA (siRNA)-mediated knockdown approaches were used to confirm the importance of of HDAC 1, 2, and 3 expression in these processes. Further, the ability of each HDAC inhibitor to induce the expression of EMT markers (RNA and protein) and EMT-like phenotype(s) (migration) were also assessed. The anti-tumor efficacy of a HDAC3-selective inhibitor, RGFP966, was compared to the pan-HDAC inhibitor Suberoylanilide Hydroxamic Acid (SAHA) in the 22Rv1 xenograft model.

RESULTS

Using genetic and pharmacological approaches we demonstrated that a useful inhibition of AR transcriptional activity, absent the induction of EMT, could be achieved by specifically inhibiting HDAC3. Significantly, we also determined that HDAC3 inhibitors blocked the activity of the constitutively active AR V7-splice variant and inhibited the growth of xenograft tumors expressing this protein.

CONCLUSIONS

Our studies provide strong rationale for the near-term development of specific HDAC3 inhibitors for the treatment of CRPC.

Abstract 1588: Effects of the selective CYP17-lyase and androgen receptor (AR) inhibitor, seviteronel, and the cyclin-dependent kinase (CDK) 4/6 inhibitor, G1T38, on tumor growth in an AR-V7+ castration-resistant prostate cancer (CRPC) xenograft model

Background: Castration-resistant prostate cancers that express the constitutively active androgen receptor (AR) variant AR-V7 exhibit significantly reduced progression-free and overall survival in response to the AR targeting agents, enzalutamide (ENZ) and abiraterone. Inhibition of Phosphoinositide-3-Kinase (PIK3CA) or CDK4/6 has been proposed as alternative therapies that directly target the cell cycle pathway in these tumors. However, the combined role of AR plus cell cycle inhibition in this treatment setting has not been established. G1T38 is a potent, selective clinical stage CDK 4/6 inhibitor. Seviteronel (SEVI) is a selective CYP17-lyase and AR inhibitor that blocks the growth of CRPC tumors with clinically relevant AR mutations, including T878A and AR-F876L. The activity of SEVI, ENZ and G1T38, alone or in combination, was evaluated using the 22Rv1 (AR-V7+) CRPC model in vitro and in vivo.

Methods: Cellular proliferation (7 days) of 22Rv1 prostate cancer cells treated with SEVI, ENZ, and G1T38 alone or in combination with SEVI or ENZA was assessed by measuring DNA content. Orchiectomized male nu/nu mice bearing 22Rv1 were randomized to receive vehicle, SEVI (150mg/kg/day p.o.), ENZ (30 mg/kg/day p.o.), G1T38 (25-100 mg/kg/day p.o.), or SEVI or ENZ in combination with G1T38. A docetaxel (20 mg/kg weekly i.p.) group was included as a standard of care comparison. Time to progression (X-fold increase in tumor volume) and tumor volume changes were assessed over a 3-7-week dosing period. Blood and tissues were collected for analysis of exposure and pharmacodynamics markers of response.

Results: SEVI and G1T38 alone or in combination, significantly reduced the proliferation of 22Rv1 cells in vitro (p<0.05). Compared to vehicle, SEVI and G1T38 monotherapy significantly inhibited tumor growth and time to progression by 1.5 and 2.5 fold, respectively (p<0.05); the combination of SEVI and G1T38 further decreased tumor growth and resulted in a 4-fold delay in progression (p<0.001). In contrast, ENZ alone was without effect on tumor growth and did not increase response to G1T38 as compared to G1T38 alone.

Conclusions: SEVI and G1T38 mono- or combination therapy significantly decreased the growth of the AR-V7+ 22Rv1 CPRC model in vitro and in vivo, an activity that distinguishes SEVI from ENZ. Therefore, combining SEVI with a CDK4/6 inhibitor such as G1T38 may be an effective therapy for the treatment of CRPC that is resistant to current standards of care.

Citation Format: Suzanne E. Wardell, Alexander P. Yllanes, John D. Norris, James P. Stice, Hannah White, Ronald A. Fleming, Jay C. Strum, William R. Moore, Donald P. McDonnell. Effects of the selective CYP17-lyase and androgen receptor (AR) inhibitor, seviteronel, and the cyclin-dependent kinase (CDK) 4/6 inhibitor, G1T38, on tumor growth in an AR-V7+ castration-resistant prostate cancer (CRPC) xenograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1588. doi:10.1158/1538-7445.AM2017-1588

Androgen receptor antagonism drives cytochrome P450 17A1 inhibitor efficacy in prostate cancer

The clinical utility of inhibiting cytochrome P450 17A1 (CYP17), a cytochrome p450 enzyme that is required for the production of androgens, has been exemplified by the approval of abiraterone for the treatment of castration-resistant prostate cancer (CRPC). Recently, however, it has been reported that CYP17 inhibitors can interact directly with the androgen receptor (AR). A phase I study recently reported that seviteronel, a CYP17 lyase-selective inhibitor, ædemonstrated a sustained reduction in prostate-specific antigen in a patient with CRPC, and another study showed seviteronel's direct effects on AR function. This suggested that seviteronel may have therapeutically relevant activities in addition to its ability to inhibit androgen production. Here, we have demonstrated that CYP17 inhibitors, with the exception of orteronel, can function as competitive AR antagonists. Conformational profiling revealed that the CYP17 inhibitor-bound AR adopted a conformation that resembled the unliganded AR (apo-AR), precluding nuclear localization and DNA binding. Further, we observed that seviteronel and abiraterone inhibited the growth of tumor xenografts expressing the clinically relevant mutation AR-F876L and that this activity could be attributed entirely to competitive AR antagonism. The results of this study suggest that the ability of CYP17 inhibitors to directly antagonize the AR may contribute to their clinical efficacy in CRPC.

CDK4/6 Therapeutic Intervention and Viable Alternative to Taxanes in CRPC

Resistance to second-generation androgen receptor (AR) antagonists and CYP17 inhibitors in patients with castration-resistant prostate cancer (CRPC) develops rapidly through reactivation of the androgen signaling axis and has been attributed to AR overexpression, production of constitutively active AR splice variants, or the selection for AR mutants with altered ligand-binding specificity. It has been established that androgens induce cell-cycle progression, in part, through upregulation of cyclin D1 (CCND1) expression and subsequent activation of cyclin-dependent kinases 4 and 6 (CDK4/6). Thus, the efficacy of the newly described CDK4/6 inhibitors (G1T28 and G1T38), docetaxel and enzalutamide, was evaluated as single agents in clinically relevant in vitro and in vivo models of hormone-sensitive and treatment-resistant prostate cancer. CDK4/6 inhibition (CDK4/6i) was as effective as docetaxel in animal models of treatment-resistant CRPC but exhibited significantly less toxicity. The in vivo effects were durable and importantly were observed in prostate cancer cells expressing wild-type AR, AR mutants, and those that have lost AR expression. CDK4/6i was also effective in prostate tumor models expressing the AR-V7 variant or the AR F876L mutation, both of which are associated with treatment resistance. Furthermore, CDK4/6i was effective in prostate cancer models where AR expression was lost. It is concluded that CDK4/6 inhibitors are a viable alternative to taxanes as therapeutic interventions in endocrine therapy-refractory CRPC.Implications: The preclinical efficacy of CDK4/6 monotherapy observed here suggests the need for near-term clinical studies of these agents in advanced prostate cancer. Mol Cancer Res; 15(6); 660-9. ©2017 AACR.

Abstract 2820: Effects of a CDK 4/6 inhibitor, G1T38, in androgen receptor sensitive and resistant models of castrate resistant prostate cancer

Introduction: Resistance to endocrine therapies, via expression of mutations or variants of the androgen receptor (AR), remains an impediment to enduring therapeutic responses in advanced castration resistant prostate cancer (CRPC). AR-dependent upregulation of cyclins leads to activation of the Cyclin D1-cyclin dependent kinase 4/6 (CDK 4/6) complex and cell proliferation, suggesting that targeting of this axis may be effective in CRPC. We have developed a series of potent and selective CDK 4/6 inhibitors, of which G1T38 has an IC50 in the low nanomolar range, and >3000 fold selectivity for CDK4/6 over CDK 2/cyclin A/E complexes. The efficacy of G1T38 was evaluated using models of CRPC; the results of which have significant clinical implications.

Methods: For proliferation assays, cells were treated for 5-10 days with G1T38 or standard of care comparators prior to quantitation of cell number/viability. Cell cycle progression and apoptosis were assayed by flow cytometry using propidium iodide or Annexin V/Sytox red staining, respectively. Orchiectomized Nu/Nu or NOD SCID Gamma mice bearing 22rV1 or LnCAP-AR-F876L xenograft tumors, respectively, were treated with G1T38 or clinically relevant comparators.

Results: G1T38 inhibited the growth of prostate cancer cell lines expressing wild type AR (LnCAP and VCAP), resistance associated AR variant AR v7 (22rV1 and LnCAP95), and LnCAP cells overexpressing the MDV3100 resistant AR mutation F876L. Corresponding decreases in cell cycle G0/G1 progression and in Rb phosphorylation (S807/811) were observed in all cell lines tested, whereas no changes were observed in Cyclin D1, E or Cdk2, 4, or 6 expression. Growth inhibition by G1T38 was dependent on Rb, and not AR, status as DU145 (AR-/Rb-) cells were not growth inhibited by G1T38, while PC3 (AR-/Rb+) were growth arrested. Treatment of G1T38 in combination with the anti-androgen MDV3100 increased the sensitivity of VCAP and 22RV1 cells to growth inhibition. Interestingly, MDV3100 in combination with G1T38 at high doses produced a synergistic apoptotic effect in LnCAP, VCAP, and 22rV1 cells, which could be attenuated by the caspase inhibitor Q-VD-OPH. The growth of 22rV1 cells and LnCAP AR F876L cells were assessed when propagated as xenografts. In 22RV1 cells, pharmacologic CDK 4/6 inhibition, significantly resulted in tumor regression compared to vehicle or docetaxel. In the LnCAP-AR-F876L xenograft model, tumor growth and doubling time was significantly decreased by low and high dose G1T38 treatment compared to control and MDV3100.

Conclusions: The CDK 4/6 inhibitor G1T38 exerts anti-proliferative effects in relevant models of CRPC when used as a stand-alone agent or when tested in combination with MDV3100. G1T38 inhibited xenograft tumor growth to a greater extent than other available therapies, highlighting the utility of CDK 4/6 inhibition in prostate cancer and a potential new paradigm in CRPC treatment.

Citation Format: James P. Stice, Hannah S. White, Suzanne E. Wardell, Alex Y. Yllanes, Scott A. Lawrence, Holly Alley, Donald P. McDonnell, Jay C. Strum. Effects of a CDK 4/6 inhibitor, G1T38, in androgen receptor sensitive and resistant models of castrate resistant prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2820.

Delineation of a FOXA1/ERα/AGR2 regulatory loop that is dysregulated in endocrine therapy-resistant breast cancer

Tamoxifen, a selective estrogen receptor (ER) modulator (SERM), remains a frontline clinical therapy for patients with ERα-positive breast cancer. However, the relatively rapid development of resistance to this drug in the metastatic setting remains an impediment to a durable response. Although drug resistance likely arises by many different mechanisms, the consensus is that most of the implicated pathways facilitate the outgrowth of a subpopulation of cancer cells that can either recognize tamoxifen as an agonist or bypass the regulatory control of ERα. Notable in this regard is the observation here and in other studies that expression of anterior gradient homology 2 (AGR2), a known proto-oncogene and disulfide isomerase, was induced by both estrogen (17β-estradiol, E2) and 4-hydroxytamoxifen (4OHT) in breast cancer cells. The importance of AGR2 expression is highlighted here by the observation that (i) its knockdown inhibited the growth of both tamoxifen-sensitive and -resistant breast cancer cells and (ii) its increased expression enhanced the growth of ERα-positive tumors in vivo and increased the migratory capacity of breast cancer cells in vitro. Interestingly, as with most ERα target genes, the expression of AGR2 in all breast cancer cells examined requires the transcription factor FOXA1. However, in tamoxifen-resistant cells, the expression of AGR2 occurs in a constitutive manner, requiring FOXA1, but loses its dependence on ER. Taken together, these data define the importance of AGR2 in breast cancer cell growth and highlight a mechanism where changes in FOXA1 activity obviate the need for ER in the regulation of this gene.

IMPLICATIONS

These findings reveal the transcriptional interplay between FOXA1 and ERα in controlling AGR2 during the transition from therapy-sensitive to -resistant breast cancer and implicate AGR2 as a relevant therapeutic target.

17β-Estradiol, aging, inflammation, and the stress response in the female heart

Heat shock proteins (HSPs) are a cardioprotective class of proteins induced by stress and regulated by the transcription factor, heat shock factor (HSF)-1. 17β-estradiol (E(2)) indirectly regulates HSP expression through rapid activation of nuclear factor-κB (NF-κB) and HSF-1 and protects against hypoxia. As males experience a loss of protective cellular responses in aging, we hypothesized that aged menopausal (old ovariectomized) rats would have an impaired HSP response, which could be prevented by immediate in vivo E(2) replacement. After measuring cardiac function in vivo, cardiac myocytes were isolated from ovariectomized adult and old rats with and without 9 weeks of E(2) replacement. Myocytes were treated with E(2) in vitro and analyzed for activation of NF-κB, HSF-1, and HSP expression. In addition, we measured inflammatory cytokine expression and susceptibility to hypoxia/reoxygenation injury. Cardiac contractility was reduced in old ovariectomized rats and could prevented by immediate E(2) replacement in vivo. Subsequent investigations in isolated cardiac myocytes found that in vitro E(2) activated NF-κB, HSF-1, and increased HSP 72 expression in adult but not old rats. In response to hypoxia/reoxygenation, myocytes from adult, but not old, rats had increased HSP 72 expression. In addition, expression of the inflammatory cytokines TNF-α and IL-1β, as well as oxidative stress, were increased in myocytes from old ovariectomized rats; only the change in cytokine expression could be attenuated by in vivo E(2) replacement. This study demonstrates that while aging in female rats led to a loss of the cardioprotective HSP response, E(2) retains its protective cellular properties.

Mechanisms of progesterone receptor inhibition of inflammatory responses in cellular models of breast cancer

Both pro- and antimitogenic activities have been ascribed to progesterone receptor (PR) agonists and antagonists in breast cancer cells; however, the transcriptional responses that underlie these paradoxical functions are not apparent. Using nontransformed, normal human mammary epithelial cells engineered to express PR and standard microarray technology, we defined 2370 genes that were significantly regulated by the PR agonist R5020. Gene ontology (GO) analysis revealed that GO terms involved in inflammation and nuclear factor-κB (NF-κB) signaling were among the most significantly regulated. Interestingly, on those NF-κB responsive genes that were inhibited by agonist-activated PR, antagonists either 1) mimicked the actions of agonists or 2) reversed the inhibitory actions of agonists. This difference in pharmacological response could be attributed to the fact that although agonist- and antagonist-activated PR is recruited to NF-κB-responsive promoters, the physical presence of PR tethered to the promoter of some genes is sufficient for transcriptional inhibition, whereas on others, an agonist-activated PR conformation is required for inhibition of NF-κB signaling. Importantly, the actions of PR on the latter class of genes were reversed by an activation function-2-inhibiting, LXXLL-containing peptide. Consideration of the relative activities of these distinct antiinflammatory pathways in breast cancer may be instructive with respect to the likely therapeutic activity of PR agonists or antagonists in the treatment of breast cancer.

Extracellular heat shock protein 60, cardiac myocytes, and apoptosis

RATIONALE

Previously, we have found that changes in the location of intracellular heat shock protein (HSP)60 are associated with apoptosis. HSP60 has been reported to be a ligand of toll-like receptor (TLR)-4.

OBJECTIVE

We hypothesized that extracellular HSP60 (exHSP60) would mediate apoptosis via TLR4.

METHODS AND RESULTS

Adult rat cardiac myocytes were treated with HSP60, either recombinant human or with HSP60 purified from the media of injured rat cardiac myocytes. ExHSP60 induced apoptosis in cardiac myocytes, as detected by increased caspase 3 activity and increased DNA fragmentation. Apoptosis could be reduced by blocking antibodies to TLR4 and by nuclear factor kappaB binding decoys, but not completely inhibited, even though similar treatment blocked lipopolysaccharide-induced apoptosis. Three distinct controls showed no evidence for involvement of a ligand other than exHSP60 in the mediation of apoptosis.

CONCLUSIONS

This is the first report of HSP60-induced apoptosis via the TLRs. HSP60-mediated activation of TLR4 may be a mechanism of myocyte loss in heart failure, where HSP60 has been detected in the plasma.

Estrogen, aging and the cardiovascular system

Estrogen is a powerful hormone with pleiotropic effects. Estrogens have potent antioxidant effects and are able to reduce inflammation, induce vasorelaxation and alter gene expression in both the vasculature and the heart. Estrogen treatment of cultured cardiac myocytes and endothelial cells rapidly activates NFkappaB, induces heat-shock protein (HSP)-72, a potent intracellular protective protein, and protects cells from simulated ischemia. In in vivo models, estrogens protect against ischemia and trauma/hemorrhage. Estrogens may decrease the expression of soluble epoxide hydrolase, which has deleterious effects on the cardiovascular system through metabolism of epoxyeicosatrienoic acids. Natural (endogenous) estrogens in premenopausal women appear to protect against cardiovascular disease and yet controlled clinical trials have not indicated a benefit from estrogen replacement postmenopause. Much remains to be understood in regards to the many properties of this powerful hormone and how changes in this hormone interact with aging-associated changes. The unexpected negative results of trials of estrogen replacement postmenopause probably arise from our lack of understanding of the many effects of this hormone.

Mitochondrial OPA1, apoptosis, and heart failure

AIMS

Mitochondrial fusion and fission are essential processes for preservation of normal mitochondrial function. We hypothesized that fusion proteins would be decreased in heart failure (HF), as the mitochondria in HF have been reported to be small and dysfunctional.

METHODS AND RESULTS

Expression of optic atrophy 1 (OPA1), a mitochondrial fusion protein, was decreased in both human and rat HF, as observed by western blotting. OPA1 is important for maintaining normal cristae structure and function, for preserving the inner membrane structure and for protecting cells from apoptosis. Confocal and electron microscopy studies demonstrated that the mitochondria in the failing hearts were small and fragmented, consistent with decreased fusion. OPA1 mRNA levels did not differ between failing and normal hearts, suggesting post-transcriptional control. Simulated ischaemia in the cardiac myogenic cell line H9c2 cells reduced OPA protein levels. Reduction of OPA1 expression with shRNA resulted in increased apoptosis and fragmentation of the mitochondria. Overexpression of OPA1 increased mitochondrial tubularity, but did not protect against simulated ischaemia-induced apoptosis. Cytochrome c release from the mitochondria was increased both with reduction in OPA1 and with overexpression of OPA1.

CONCLUSION

This is the first report, to our knowledge, of changes in mitochondrial fusion/fission proteins in cardiovascular disease. These changes have implications for mitochondrial function and apoptosis, contributing to the cell loss which is part of the downward progression of the failing heart.

Role of aging versus the loss of estrogens in the reduction in vascular function in female rats

Although aging is known to lead to increased vascular stiffness, the role of estrogens in the prevention of age-related changes in the vasculature remains to be elucidated. To address this, we measured vascular function in the thoracic aorta in adult and old ovariectomized (ovx) rats with and without immediate 17beta-estradiol (E2) replacement. In addition, aortic mRNA and protein were analyzed for proteins known to be involved in vasorelaxation. Aging in combination with the loss of estrogens led to decreased vasorelaxation in response to acetylcholine and sodium nitroprusside, indicating either smooth muscle dysfunction and/or increased fibrosis. Loss of estrogens led to increased vascular tension in response to phenylephrine, which could be partially restored by E2 replacement. Levels of endothelial nitric oxide synthase and inducible nitric oxide synthase did not differ among the groups, nor did total nitrite plus nitrate levels. Old ovx exhibited decreased expression of both the alpha and beta-subunits of soluble guanylyl cyclase (sGC) and had impaired nitric oxide signaling in the vascular smooth muscle. Immediate E2 replacement in the aged ovx prevented both the impairment in vasorelaxation, and the decreased sGC receptor expression and abnormal sGC signaling within the vascular smooth muscle.

Effects of dietary decosahexaenoic acid (DHA) on eNOS in human coronary artery endothelial cells

Endothelial dysfunction occurs in heart disease and may reduce functional capacity via attenuations in peripheral blood flow. Dietary decosahexaenoic acid (DHA) may improve this dysfunction, but the mechanism is unknown. This study determined if DHA enhances expression and activity of eNOS in cultured human coronary artery endothelial cells (HCAEC). HCAEC from 4 donors were treated with 5 nM, 50 nM, or 1 microM DHA for 7 days to model chronic DHA exposure. A trend for increased expression of endothelial nitric oxide synthase (eNOS) and phospho-eNOS was observed with 5 and 50 nM DHA. DHA also enhanced expression of 2 proteins instrumental in activation of eNOS: phospho-Akt (5 and 50 nM) and HSP90 (50 nM and 1 microM). Vascular endothelial growth factor-induced activation of Akt increased NOx in treated (50 nM DHA) versus untreated HCAEC (9.2 +/- 1.0 vs 3.3 +/- 1.1 micromol/microg protein/microL). Findings suggest that DHA enhances eNOS and Akt activity, augments HSP90 expression, and increases NO bioavailability in response to Akt kinase activation.

Estrogen, NFkappaB, and the heat shock response

Estrogen has pleiotropic actions, among which are its anti-apoptotic, anti-inflammatory, and vasodilatory effects. Recently, an interaction between 17beta-estradiol (E2) and the transcription factor nuclear factor kappaB (NFkappaB) has been identified. NFkappaB has a central role in the control of genes involved in inflammation, proliferation, and apoptosis. Prolonged activation of NFkappaB is associated with numerous inflammatory pathological conditions. An important facet of E2 is its ability to modulate activity of NFkappaB via both genomic and nongenomic actions. E2 can activate NFkappaB rapidly via nongenomic pathways, increase cellular resistance to injury, and induce expression of the protective class of proteins, heat shock proteins (HSPs). HSPs can bind to many of the pro-apoptotic and pro-inflammatory targets of NFkappaB and, thus, indirectly inhibit many of its deleterious effects. In addition, HSPs can block NFkappaB activation and binding directly. Similarly, genomic E2 signaling can inhibit NFkappaB, but does so through alternative mechanisms. This review focuses on the molecular mechanisms of cross-talk between E2, NFkappaB, and HSPs, and the biological relevance of this cross-talk.

Triglyceride-Rich Lipoproteins Prime Aortic Endothelium for an Enhanced Inflammatory Response to Tumor Necrosis Factor-α

High levels of triglyceride-rich lipoproteins (TGRLs) in blood are linked to development of atherosclerosis, yet the mechanisms by which these particles initiate inflammation of endothelium are unknown. TGRL isolated from human plasma during the postprandial state was examined for its capacity to bind to cultured human aortic endothelial cells (HAECs) and alter the acute inflammatory response to tumor necrosis factor-α. HAECs were repetitively incubated with dietary levels of freshly isolated TGRL for 2 hours per day for 1 to 3 days to mimic postprandial lipidemia. TGRL induced membrane upregulation of the low-density lipoprotein family receptors LRP and LR11, which was inhibited by the low-density lipoprotein receptor-associated protein-1. TGRLs alone did not elicit inflammation in HAECs but enhanced the inflammatory response via a 10-fold increase in sensitivity to cytokine stimulation. This was reflected by increased mitogen-activated protein kinase activation, nuclear translocation of NF-κB, amplified expression of endothelial selectin and VCAM-1, and a subsequent increase in monocyte-specific recruitment under shear flow as quantified in a microfabricated vascular mimetic device.

Effect of mutation of amino acids 246-251 (KRKHKK) in HSP72 on protein synthesis and recovery from hypoxic injury

Heat shock protein (HSP)72, the inducible form of HSP70, protects cells against a variety of injuries, but underlying mechanisms are poorly defined. To investigate the protective effects of HSP72, multiple clones expressing wild-type (WT) HSP72 and two mutants with defective nucleolar and nuclear localization (M45 and 985A, respectively) were made with the tet-off system in C2C12 cells. Four different parameters of cell function/injury were examined after simulated ischemia: protein synthesis, polysome formation, DNA synthesis, and lactate dehydrogenase (LDH release). Overexpression of WT HSP72 was also compared to nontransfected C2C12 cells. As expected, overexpression of HSP72 protected against simulated ischemia and reoxygenation for all parameters. In contrast, both M45 and 985A showed abnormal protein synthesis and polysome formation, both after simulated ischemia and under control conditions. Total RNA was slightly reduced in M45 and 985A at baseline, but 1 h after hypoxia, RNA levels were protected in all clones but significantly decreased in nontransfected C2C12 cells. Clones expressing 985A had nuclear retention of mRNA, suggesting that HSP72 is needed for nuclear export of RNA. All clones, both WT and mutant, had protection of DNA synthesis compared to C2C12 cells, but 985A had greater release of LDH after injury than any other group. These results support a multifactoral protective effect of HSP72, some aspects dependent on nuclear localization with stress and some not. The protection of protein synthesis and polysome formation, and abnormalities in these with the mutants, support a role for HSP72 in these processes both in the normal cell and in injury.