Genomic Hallmarks and Structural Variation in Metastatic Prostate Cancer.

While mutations affecting protein-coding regions have been examined across many cancers, structural variants at the genome-wide level are still poorly defined. Through integrative deep whole-genome and -transcriptome analysis of 101 castration-resistant prostate cancer metastases (109X tumor/38X normal coverage), we identified structural variants altering critical regulators of tumorigenesis and progression not detectable by exome approaches. Notably, we observed amplification of an intergenic enhancer region 624 kb upstream of the androgen receptor (AR) in 81% of patients, correlating with increased AR expression. Tandem duplication hotspots also occur near MYC, in lncRNAs associated with post-translational MYC regulation. Classes of structural variations were linked to distinct DNA repair deficiencies, suggesting their etiology, including associations of CDK12 mutation with tandem duplications, TP53 inactivation with inverted rearrangements and chromothripsis, and BRCA2 inactivation with deletions. Together, these observations provide a comprehensive view of how structural variations affect critical regulators in metastatic prostate cancer.

CsPbBr3 Perovskite Crack Platelet Nanocrystals and Their Biexciton Generation.

Lead halide perovskite nanocrystals have been extensively studied in recent years as efficient optical materials for their bright and color-tunable emissions. However, these are mostly confined to their 3D nanocrystals and limited to the anisotropic nanostructures. By exploring the Cs-sublattice-induced metal(II) ion exchange with Pb(II), crack CsPbBr3 perovskite platelet nanocrystals having polar surfaces in all three directions are reported here, which remained different than reported standard square platelets. The crack platelets are also passivated with halides to enhance their brightness. Further, as these crack and passivated crack platelets have defects and polar surfaces, the exciton and biexciton generation in these platelets is investigated using femtosecond photoluminescence and transient absorption measurement at ambient as well as cryogenic temperatures, correlated with time-resolved single-particle photoluminescence spectroscopy, and compared with standard square platelets having nonpolar facets. These investigations revealed that the crack platelets and passivated crack platelets possess enhanced biexciton emission compared to square platelets due to the presence of polar surfaces in all three directions. These results provide insights into not only the design of the anisotropic nanostructures of ionic nanocrystals but also the possibility of tuning the single exciton to biexciton generation efficiency, which has potential applications in optoelectronic systems.

MITOL-mediated DRP1 ubiquitylation and degradation promotes mitochondrial hyperfusion in a CMT2A-linked MFN2 mutant.

Mutations in mitofusin 2 (MFN2) that are associated with the pathology of the debilitating neuropathy Charcot-Marie-Tooth type 2A (CMT2A) are known to alter mitochondrial morphology. One such abundant MFN2 mutation, R364W, results in the generation of elongated, interconnected mitochondria. However, the mechanism leading to this mitochondrial aberration remains poorly understood. Here, we show that mitochondrial hyperfusion in the presence of R364W-MFN2 is due to increased degradation of DRP1 (also known as DNM1L). The E3 ubiquitin ligase MITOL (also known as MARCHF5) is known to ubiquitylate both MFN2 and DRP1. Interaction with and subsequent ubiquitylation by MITOL is stronger in the presence of wild-type MFN2 than with R364W-MFN2. This differential interaction of MITOL with MFN2 in the presence of R364W-MFN2 renders the ligase more available for DRP1 ubiquitylation. Multi-monoubiquitylation and proteasomal degradation of DRP1 in R364W-MFN2 cells in the presence of MITOL eventually leads to mitochondrial hyperfusion. Here, we provide a mechanistic insight into mitochondrial hyperfusion, while also reporting that MFN2 can indirectly modulate DRP1 - an effect not shown previously. This article has an associated First Person interview with the first author of the paper.

Cysteine-free cone snail venom peptides: Classification of precursor proteins and identification of mature peptides.

The cysteine-free acyclic peptides present in marine cone snail venom have been much less investigated than their disulfide bonded counterparts. Precursor protein sequences derived from transcriptomic data, together with mass spectrometric fragmentation patterns for peptides present in venom duct tissue extracts, permit the identification of mature peptides. Twelve distinct gene superfamiles have been identified with precursor lengths between 64 and 158 residues. In the case of Conus monile, three distinct mature peptides have been identified, arising from two distinct protein precursors. Mature acyclic peptides are often post-translationally modified, with C-terminus amidation, a feature characteristic of neuropeptides. In the present study, 20 acyclic peptides from Conus monile and Conus betulinus were identified. The common modifications of C-terminus amidation, gamma carboxylation of glutamic acid (E to ϒ), N-terminus conversion of Gln (Q) to a pyroglutamyl residue (Z), and hydroxylation of Pro (P) to Hyp (O) are observed in one or more peptides identified in this study. Proteolytic trimming of sequences by cleavage at the C-terminus of Asn (N) residues is established. The presence of an asparagine endopeptidase is strengthened by the identification of legumain-like sequences in the transcriptome assemblies from diverse Conus species. Such sequences may be expected to have a cleavage specificity at Asn-Xxx peptide bonds.

Schistura sonarengaensis, a new species of cave-dwelling loach (Teleostei: Nemacheilidae) from Meghalaya, northeast India.

A new species of nemacheilid loach, Schistura sonarengaensis sp. nov., is described from three cave-dwelling populations (Barak-Surma-Meghna drainage) in the South Garo Hills district of Meghalaya, India. The new species possesses prominent eyes but is easily distinguished from all the congeners of the genus Schistura from Barak-Surma-Meghna and adjacent rivers drainages of northeast Indian (except S. syngkai) in having 13-26 vertically elongated to circular mid-lateral black blotches (brownish in life) overlayered on a grayish-black mid-lateral stripe on a dull white or pale-beige (golden brown in life) body. However, it can be easily distinguished from S. syngkai in having a complete (vs. incomplete) lateral line with more 72-89 (vs. 19-42) lateral-line pored scales, greater pre-dorsal length (48.5-53.1 vs. 41.9-44.1 %SL), a wider body at dorsal-fin origin (11.3-16.7 vs. 9.4-10.3 %SL), greater dorsal (18.1-21.1 vs. 15.1-17.0 %SL) and lateral (20.9-24.1 vs. 17.4-18.9 %SL) head length, a wider head (14.5-18.5 vs. 11.6-13.3 %SL), and moderately forked (vs. emarginated) caudal fin. Further, molecular analysis confirms the distinctiveness of S. sonarengaensis sp. nov. from its congeners found in northeast India by significant divergences with uncorrected genetic distance ranging from 3.7% to 17.3% in the mitochondrial cytochrome c oxidase subunit I (COI) gene dataset. The phylogenetic position of the new species with its sister species was evaluated using maximum likelihood and Bayesian analysis. The species delimitation approaches assemble species by automatic partitioning (ASAP) and Poisson tree processes (PTP) utilized for testing species assignments consistently identified our test group as a distinct species from its sister species. Although the new species lacks typical morphological adaptations usually associated with a subterranean life, such as complete absence (or vestigial presence) of eyes and pigmentation, it exhibits a reduction of pigmentation when compared to the epigean congeners.

CMT2A-linked mitochondrial hyperfusion-driving mutant MFN2 perturbs ER-mitochondrial associations and Ca2+ homeostasis.

BACKGROUND INFORMATION: Mitofusin2 (MFN2), an important molecular player that regulates mitochondrial fusion, also helps maintain the inter-organellar contact sites, referred as mitochondria associated membranes (MAMs) that exist between the ER and mitochondria. The study deals with a mutant of MFN2, R364W-MFN2, linked with the neuropathy, Charcot Marie Tooth (CMT) disease. Previous studies show that this mutant promotes mitochondrial hyperfusion. Here, we try to decipher the role of R364W-MFN2 in affecting the ER mitochondrial associations at the MAM junctions and inter-organellar calcium signalling between the ER and the mitochondria. RESULTS: Our results show that R364W-MFN2 altered ER-mitochondria association at the MAM junctions, predisposed mitochondria towards cellular stress with the mitochondria undergoing rapid fission upon induction of mild stress and perturbs inter-organellar calcium homeostasis. CONCLUSION: The results indicate that R364W-MFN2 not only affects mitochondrial morphology and dynamics but also modulate its interaction with the ER and Ca2+ signalling between the two organelles. SIGNIFICANCE: This study provides significant insight that presence of the R364W-MFN2 mutation makes cells susceptible towards stress, thus negatively affecting cellular health which altogether might culminate in the form of the CMT neuropathy.

Identification and characterisation of emerging fish pathogens Aeromonas veronii and Aeromonas hydrophila isolated from naturally infected Channa punctata.

Naturally infected Channa punctata exhibiting bacterial septicemic syndrome including ulcerations along with mortality records were collected from a fish farm in Assam during winter season (early November 2020 to early January 2021). The moribund fishes were subjected for bacterial isolation followed by identification of the bacteria. Two dominant emerging bacterial pathogens were identified as Aeromonas veronii (isolate ZooGURD-01) and Aeromonas hydrophila (isolate ZooGURD-05) by standard biochemical characterization and 16S rRNA and rpo B gene amplification. Re-infection experiments of both the bacterial isolates in healthy disease-free C. punctata showed similar symptoms to that of natural infection thus confirming their virulence. The LD50 calculated during challenge test for both the isolates ZooGURD-01 and ZooGURD-05 found to be pathogenic at 2.6 × 104 and 1.6 × 104 CFU/fish respectively. Further PCR amplification of specific virulent genes (aerolysin, hemolysin and enterotoxin) confirmed pathogenicity for both isolates. Histopathological examinations of liver and kidney in re-infection experiments showed prominent changes supporting bacterial septicaemia. Antibiotic sensitivity pattern showed that the isolates ZooGURD-01 and ZooGURD-05 were sensitive to 22 and 19 out of 25 antimicrobials respectively. The present study was the first report on the mortality of farmed C. punctata associated with natural infection caused by A. veronii and A. hydrophila with no record of pathogenicity of A. veronii in C. punctata.

Tuning Crystal Plane Orientation in Multijunction and Hexagonal Single Crystalline CsPbBr3 Perovskite Disc Nanocrystals.

Two-dimensional-shaped CsPbBr3 platelet nanocrystals are widely studied for their bright high energy emission and self-assembly. These nanostructures are in orthorhombic phase, have a square shape, and have the vertical axis [001] perpendicular to the basal plane. Moreover, these are mostly single-crystalline structures with a continuous lattice and appear like slices of cube nanocrystals. In contrast, herein, multijunction and hexagonal single crystalline 2D discs of CsPbBr3 are reported to have all their vertical axes [100]. These are obtained by using the perovskite derivative of tetragonal Cs3MnBr5 as the parent material and subsequent B-site Pb(II) introduction in the presence of phenacyl bromide at different reaction temperatures. At low temperature, multijunction discs having random orientations of two horizontal axes [010] and [001] from one to another segment are observed. Orientations of planes remained random as both coherent and incoherent twin planes were observed at their boundaries. However, the number of junctions/segments was reduced at higher temperature, and finally hexagonal single crystalline discs remained as the ultimate product. Analysis suggested that the crystal nature of parent Cs3MnBr5 and temperature-dependent variation in the rate of Pb(II) insertions determined the nature of discs having randomly oriented or static planes in the entire nanostructure. Not only in 2D discs but also, 3D nanocrystals having similar segments with different orientations are formed upon Pb(II) exchange with Mn(II) alloyed cubic CsBr. Hexagonal single crystalline and segmented multijunction CsPbBr3 discs remain unique among 2D perovskites nanostructures, and their formation mechanism indeed introduced new fundamentals of the crystallization process of these emerging energy materials.

Facets-Directed Epitaxially Grown Lead Halide Perovskite-Sulfobromide Nanocrystal Heterostructures and Their Improved Photocatalytic Activity.

Lead halide perovskite nanocrystal heterostructures have been extensively studied in the recent past for improving their photogenerated charge carriers mobility. However, most of such heterostructures are formed with random connections without having strong evidence of epitaxial relation. Perovskite-chalcohalides are the first in this category, where all-inorganic heterostructures are formed with epitaxial growth. Going beyond one facet, herein, different polyhedral nanocrystals of CsPbBr3 are explored for facet-selective secondary epitaxial sulfobromide growths. Following a decoupled synthesis process, the heterojunctions are selectively established along {110} as well as {200} facets of 26-faceted rhombicuboctahedrons, the {110} facets of armed hexapods, and the {002} facets of 12-faceted dodecahedron nanocrystals of orthorhombic CsPbBr3. Lattice matching induced these epitaxial growths, and their heterojunctions have been extensively studied with electron microscopic imaging. Unfortunately, these heterostructures did not retain the intense host emission because of their indirect band structures, but such combinations are found to be ideal for promoting photocatalytic CO2 reduction. The pseudo-Type-II combination helped here in the successful movement of charge carriers and also improved the rate of catalysis. These results suggest that facet-selective all-inorganic perovskite heterostructures can be epitaxially grown and this could help in improving their catalytic activities.

Sickle Cell Hemoglobin.

Sickle cell hemoglobin (HbS) is an example of a genetic variant of human hemoglobin where a point mutation in the ß globin gene results in substitution of glutamic acid to valine at sixth position of the ß globin chain. Association between tetrameric hemoglobin molecules through noncovalent interactions between side chain residue of ßVal6 and hydrophobic grooves formed by ßAla70, ßPhe85 and ßLeu88 amino acid residues of another tetramer followed by the precipitation of the elongated polymer leads to the formation of sickle-shaped RBCs in the deoxygenated state of HbS. There are multiple non-covalent interactions between residues across intra- and inter-strands that stabilize the polymer. The clinical phenotype of sickling of RBCs manifests as sickle cell anemia, which was first documented in the year 1910 in an African patient. Although the molecular reason of the disease has been understood well over the decades of research and several treatment procedures have been explored to date, an effective therapeutic strategy for sickle cell anemia has not been discovered yet. Surprisingly, it has been observed that the oxy form of HbS and glutathionylated form of deoxy HbS inhibits polymerization. In addition to describe the residue level interactions in the HbS polymer that provides its stability, here we explain the mechanism of inhibition in the polymerization of HbS in its oxy state. Additionally, we reported the molecular insights of inhibition in the polymerization for glutathionyl HbS, a posttranslational modification of hemoglobin, even in its deoxy state. In this chapter we briefly consider the available treatment procedures of sickle cell anemia and propose that the elevation of glutathionylation of HbS within RBCs, without inducing oxidative stress, might be an effective therapeutic strategy for sickle cell anemia.

Description of a new species of Mustura Kottelat (Teleostei: Nemacheilidae) from the Brahmaputra drainage, India.

Mustura subhashi, new species, is described from the Dikal River, a north bank tributary of the Brahmaputra drainage in Arunachal Pradesh. It is distinguished from all its congeners by having a colour pattern of 14-23 dark-greyish black to dark brown irregular bars on a greyish to pale beige body; pre-dorsal bars thin, numerous, wider than interspaces, weakly contrasted, uniting dorsally at lateral one-third or midway on flank to form thicker bars, coalescing further at lateral one-fifth and continuous on dorsum with contralateral bars; bars below dorsal fin exhibiting similar condition but slightly wider than pre-dorsal bars; post-dorsal bars thicker than anterior bars, wider than interspaces, sharply contrasted, rarely coalescing on flank; and a short bar along the caudal mid-line, rarely forming a blotch. Based on re-examination of the type specimens and additional materials, Mustura dikrongensis is confirmed as a species belonging to Mustura, and M. harkishorei is not sufficiently diagnosed from 'Nemacheilus' corica.

Mitochondrial hyperfusion: a friend or a foe.

The cellular mitochondrial population undergoes repeated cycles of fission and fusion to maintain its integrity, as well as overall cellular homeostasis. While equilibrium usually exists between the fission-fusion dynamics, their rates are influenced by organellar and cellular metabolic and pathogenic conditions. Under conditions of cellular stress, there is a disruption of this fission and fusion balance and mitochondria undergo either increased fusion, forming a hyperfused meshwork or excessive fission to counteract stress and remove damaged mitochondria via mitophagy. While some previous reports suggest that hyperfusion is initiated to ameliorate cellular stress, recent studies show its negative impact on cellular health in disease conditions. The exact mechanism of mitochondrial hyperfusion and its role in maintaining cellular health and homeostasis, however, remain unclear. In this review, we aim to highlight the different aspects of mitochondrial hyperfusion in either promoting or mitigating stress and also its role in immunity and diseases.

Identification of Novel Response and Predictive Biomarkers to Hsp90 Inhibitors Through Proteomic Profiling of Patient-derived Prostate Tumor Explants.

Inhibition of the heat shock protein 90 (Hsp90) chaperone is a promising therapeutic strategy to target expression of the androgen receptor (AR) and other oncogenic drivers in prostate cancer cells. However, identification of clinically-relevant responses and predictive biomarkers is essential to maximize efficacy and treatment personalization. Here, we combined mass spectrometry (MS)-based proteomic analyses with a unique patient-derived explant (PDE) model that retains the complex microenvironment of primary prostate tumors. Independent discovery and validation cohorts of PDEs (n = 16 and 30, respectively) were cultured in the absence or presence of Hsp90 inhibitors AUY922 or 17-AAG. PDEs were analyzed by LC-MS/MS with a hyper-reaction monitoring data independent acquisition (HRM-DIA) workflow, and differentially expressed proteins identified using repeated measure analysis of variance (ANOVA; raw p value <0.01). Using gene set enrichment, we found striking conservation of the most significantly AUY922-altered gene pathways between the discovery and validation cohorts, indicating that our experimental and analysis workflows were robust. Eight proteins were selectively altered across both cohorts by the most potent inhibitor, AUY922, including TIMP1, SERPINA3 and CYP51A (adjusted p < 0.01). The AUY922-mediated decrease in secretory TIMP1 was validated by ELISA of the PDE culture medium. We next exploited the heterogeneous response of PDEs to 17-AAG in order to detect predictive biomarkers of response and identified PCBP3 as a marker with increased expression in PDEs that had no response or increased in proliferation. Also, 17-AAG treatment led to increased expression of DNAJA1 in PDEs that exhibited a cytostatic response, revealing potential drug resistance mechanisms. This selective regulation of DNAJA1 was validated by Western blot analysis. Our study establishes "proof-of-principle" that proteomic profiling of drug-treated PDEs represents an effective and clinically-relevant strategy for identification of biomarkers that associate with certain tumor-specific responses.

Molecular insights of inhibition in sickle hemoglobin polymerization upon glutathionylation: hydrogen/deuterium exchange mass spectrometry and molecular dynamics simulation-based approach.

In sickle cell anemia, polymerization of hemoglobin in its deoxy state leads to the formation of insoluble fibers that result in sickling of red blood cells. Stereo-specific binding of isopropyl group of ßVal6, the mutated amino-acid residue of a tetrameric sickle hemoglobin molecule (HbS), with hydrophobic groove of another HbS tetramer initiates the polymerization. Glutathionylation of ßCys93 in HbS was reported to inhibit the polymerization. However, the mechanism of inhibition in polymerization is unknown to date. In our study, the molecular insights of inhibition in polymerization were investigated by monitoring the conformational dynamics in solution phase using hydrogen/deuterium exchange-based mass spectrometry. The conformational rigidity imparted due to glutathionylation of HbS results in solvent shielding of ßVal6 and perturbation in the conformation of hydrophobic groove of HbS. Additionally, molecular dynamics simulation trajectory showed that the stereo-specific localization of glutathione moiety in the hydrophobic groove across the globin subunit interface of tetrameric HbS might contribute to inhibition in polymerization. These conformational insights in the inhibition of HbS polymerization upon glutathionylation might be translated in the molecularly targeted therapeutic approaches for sickle cell anemia.

Analysis of the Quaternary Structure of Hemoglobin Beckman Variant and Molecular Interpretation of Its Functional Abnormality: A Mass-Spectrometry-Based Approach.

Electrostatic attraction between α and ß globin chains holds the subunits together in a tetrameric human hemoglobin molecule (α2 ß2 ). Compared to normal globin chains, the affinity of a mutant chain to its partner globin might be different in genetic variants of hemoglobin. This leads to an unequal abundance of normal and variant hemoglobin in heterozygous samples, even though the rates of synthesis of both the normal and variant chains are the same. The aforementioned affinities across various globin chains might be assessed by quantification of the different forms of the tetramers present in a variant hemoglobin sample. In the present study, by exploiting mass differences between globin chains, differently populated hemoglobin tetramers present in hemoglobin (Hb) Beckman, a ß variant (ßA135D), were structurally characterized. The relative populations of dissymmetric tetramers (α2 ß2 , α2 ßßV , and α2 ßV2 ) indicated that both ß and ßV have different affinities towards the α globin chain. Conformational dynamics analyzed from hydrogen/deuterium exchange kinetics of the three peptide fragments of Hb Beckman in its oxy state displayed molecular insight into its functional abnormality. However, in comparison to normal hemoglobin (α2 ß2 ), the point mutation did not show any change in the collision cross-sections of the functionally active conformers of the variant hemoglobin molecules (α2 ßßV and α2 ßV2 ).

Application of isotope exchange based mass spectrometry to understand the mechanism of inhibition of sickle hemoglobin polymerization upon oxygenation.

Sickle hemoglobin (HbS) polymerization initiates in the deoxy state with the binding of hydrophobic patch formed by the isopropyl group of ßVal6 residue of a hemoglobin tetramer with the hydrophobic pocket of another tetramer, whose hydrophobic patch binds to the hydrophobic groove of a third molecule. Subsequent elongation of a single stranded polymer followed by the formation of a double strand and finally combination of seven such pairs of double strands results in a fourteen stranded fibrous polymer. Precipitation of this fiber inside the erythrocytes results in sickling of red blood cells. Surprisingly, the polymerization does not occur in the oxy state of HbS. Due to the unavailability of crystal structure of oxy form of HbS, the molecular basis of inhibition of polymerization in the oxy state is unknown to date. In the present study, we have attempted to understand the molecular mechanism of inhibition of polymerization by exploiting the exchange of backbone amide hydrogens of HbS with deuterated solvent. Hydrogen/deuterium exchange kinetics of peptide amide hydrogens of both oxy and deoxy form of HbS were monitored through ESI mass spectrometry. Upon oxygenation changes in the conformational flexibility across different regions of α and ß globin chains in the tetrameric HbS molecule were investigated. It was observed that oxygenation led to perturbation in the conformation of several residues around the hydrophobic patch, groove of a tetramer and axial, lateral contacts across the double strands that are involved in HbS polymerization.

Assessment of Cysteine Reactivity of Human Hemoglobin at Its Residue Level: A Mass Spectrometry-Based Approach.

In general, the reactivity of cysteine residues of proteins is measured by 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) kinetics using spectrophotometry. Proteins with several cysteine residues may exhibit varying DTNB kinetics but residue level information can only be obtained with the prior knowledge of their three-dimensional structure. However, this method is limited in its application to the proteins containing chromophores having overlapping absorption profile with 2-nitro-5-thiobenzoic acid, such as hemoglobin (Hb). Additionally, this method is incapable of assigning cysteine reactivity at the residue levels of proteins with unknown crystal structures. However, a mass spectrometry (MS)-based platform might provide a solution to these problems. In the present study, alkylation kinetics of cysteine residues of adult human Hb (Hb A; α2ß2) and sickle cell Hb (Hb S; HBB: c.20A>T) were investigated using matrix-assisted laser desorption/ionization (MALDI) MS. Differential site-specific reactivities of cysteine residues of Hb were investigated using alkylation kinetics with iodoacetamide (IAM). The observed reactivities corroborated well with the differential surface accessibilities of cysteine residues in the crystal structures of human Hb. The proposed method might be used to investigate cysteine reactivities of all the genetic and post-translational variants of Hb discovered to date. In addition, this method can be extended to explore cysteine reactivities of proteins, irrespective of the presence of chromophores and availability of crystal structures.

A Novel Class of Hsp90 C-Terminal Modulators Have Pre-Clinical Efficacy in Prostate Tumor Cells Without Induction of a Heat Shock Response.

BACKGROUND: While there is compelling rationale to use heat shock protein 90 (Hsp90) inhibitors for treatment of advanced prostate cancer, agents that target the N-terminal ATP-binding site of Hsp90 have shown little clinical benefit. These N-terminal binding agents induce a heat shock response that activates compensatory heat shock proteins, which is believed to contribute in part to the agents' lack of efficacy. Here, we describe the functional characterization of two novel agents, SM253 and SM258, that bind the N-middle linker region of Hsp90, resulting in reduced client protein activation and preventing C-terminal co-chaperones and client proteins from binding to Hsp90. METHODS: Inhibition of Hsp90 activity in prostate cancer cells by SM253 and SM 258 was assessed by pull-down assays. Cell viability, proliferation and apoptosis were assayed in prostate cancer cell lines (LNCaP, 22Rv1, PC-3) cultured with N-terminal Hsp90 inhibitors (AUY922, 17-AAG), SM253 or SM258. Expression of HSR heat shock proteins, Hsp90 client proteins and co-chaperones was assessed by immunoblotting. Efficacy of the SM compounds was evaluated in human primary prostate tumors cultured ex vivo by immunohistochemical detection of Hsp70 and Ki67. RESULTS: SM253 and SM258 exhibit antiproliferative and pro-apoptotic activity in multiple prostate cancer cell lines (LNCaP, 22Rv1, and PC-3) at low micromolar concentrations. Unlike the N-terminal inhibitors AUY922 and 17-AAG, these SM agents do not induce expression of Hsp27, Hsp40, or Hsp70, proteins that are characteristic of the heat shock response, in any of the prostate cell lines analyzed. Notably, SM258 significantly reduced proliferation within 2 days in human primary prostate tumors cultured ex vivo, without the significant induction of Hsp70 that was caused by AUY922 in the tissues. CONCLUSIONS: Our findings provide the first evidence of efficacy of this class of C-terminal modulators of Hsp90 in human prostate tumors, and indicate that further evaluation of these promising new agents is warranted. Prostate 76:1546-1559, 2016. © 2016 Wiley Periodicals, Inc.