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Objective: ERG rearrangements are frequent and early events in prostate cancer. The functional role of rearranged ERG, however, is still incompletely understood. ERG rearrangements are maintained during prostate cancer progression suggesting that they may confer a selective advantage. The molecular basis of this notion is the subject of this study., Methods: A variety of immunological methods were used to characterize the effects of rearranged ERG on p53. Consequences of an overexpression of N-terminally deleted ERG on p53 function were interrogated by measuring apoptosis and cellular senescence in the presence or absence of exogenous DNA damage. Effects of N-terminally deleted ERG on the transactivation function of p53 were analyzed by qRT-PCR., Results: We show that overexpression of ERG leads to an increased basal level of DNA damage and a stabilization of p53 that involves a sequestration of its E3 ubiquitin ligase, MDM2, into nucleoli. A higher p53 expression was also observed in vivo in an ERG-overexpressing prostatic intraepithelial neoplasia mouse model. The correlation between ERG and p53 expression was corroborated in 163 patients with prostate cancer. ERG overexpression was found to inhibit both apoptosis and cellular senescence induced by exogenous DNA damage. Mechanistically, this protective effect of ERG involved an abrogation of the DNA damage-induced expression of p53 target genes., Conclusions: By protecting tumor cells from the antiproliferative consequences of genotoxic stress, ERG may allow the survival and proliferation of genomically unstable tumor cells. Targeting ERG may therefore represent a promising strategy to suppress such adverse features during prostate cancer progression., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

The majority of gastrointestinal stromal tumors (GISTs) are driven by oncogenic KIT signaling and can therefore be effectively treated with the tyrosine kinase inhibitor (TKI) imatinib mesylate. However, most GISTs develop imatinib resistance through secondary KIT mutations. The type of resistance mutation determines sensitivity to approved second-/third-line TKIs but shows high inter- and intratumoral heterogeneity. Therefore, therapeutic strategies that target KIT independently of the mutational status are intriguing. Inhibiting the ubiquitin-proteasome machinery with bortezomib is effective in GIST cells through a dual mechanism of KIT transcriptional downregulation and upregulation of the pro-apoptotic histone H2AX but clinically problematic due to the drug's adverse effects. We therefore tested second-generation inhibitors of the 20S proteasome (delanzomib, carfilzomib and ixazomib) with better pharmacologic profiles as well as compounds targeting regulators of ubiquitination (b-AP15, MLN4924) for their effectiveness and mechanism of action in GIST. All three 20S proteasome inhibitors were highly effective in vitro and in vivo, including in imatinib-resistant models. In contrast, b-AP15 and MLN4924 were only effective at high concentrations or had mostly cytostatic effects, respectively. Our results confirm 20S proteasome inhibitors as promising strategy to overcome TKI resistance in GIST, while highlighting the complexity of the ubiquitin-proteasome machinery as a therapeutic target.

Background: There is mounting evidence to suggest that stromal cells play an integral role in the progression of prostate cancer (PCa). One of the most frequently altered growth factors in PCa is fibroblast growth factor-2 (FGF-2). It has previously been proposed that early stages of PCa are characterized by a primarily exogenous, that is, stromal cell-derived FGF-2 production, whereas advanced tumors rely more on an autocrine FGF-2 production. Prostate cancer progression is characterized by an increase of genomic instability including aneuploidy and structural chromosomal alterations. Herein, we address 2 problems that have not been comprehensively answered. First, we ask whether exogenous FGF-2 can directly drive genomic instability to promote PCa progression. Second, we investigate whether and to what extent stromal FGF-2 expression is maintained in advanced PCa and whether this influences tumor progression and patient prognosis., Methods: In vitro experiments to investigate the role of FGF-2 in numerical and structural chromosomal instability were performed using immunofluorescence microscopy, fluorescence in situ hybridization and single cell electrophoresis. A human patient-derived xenograft mouse model recapitulating osteoblastic PCa bone metastasis was used for in vivo validation experiments. The prognostic role of stromal FGF-2 expression was analyzed using immunohistochemical staining of a tissue microarray with primary tumor specimens from 162 predominantly high-risk patients with PCa., Results: Our results show that FGF-2 not only rapidly induces mitotic defects and numerical chromosomal imbalances but also an enhanced DNA breakage to promote chromosomal instability. Using the patient-derived xenograft model, we show that a deregulation of the FGF axis results in an increase of mitotic aberrations as well as DNA damage checkpoint activation in vivo. The FGFR inhibitor dovitinib was found to reduce numerical chromosomal instability as well as DNA breakage, thus underscoring the relevance of the FGF axis in promoting genomic instability. An overexpression of tumor cell-associated FGF-2 was detected in 52 of 162 patients (32.1%), whereas a stromal overexpression was found in 27 of 165 patients (16%). Remarkably, a strong stromal FGF-2 expression was associated with a significantly higher clinical stage and higher biochemical recurrence rate. Patients with strong stromal FGF-2 expression also had a significantly worse biochemical recurrence-free survival., Conclusions: Our results underscore that exogenous FGF-2 can shape PCa cell genomes and that stromal FGF-2 expression is detectable in a sizeable proportion of advanced PCa where it is associated with adverse clinico-pathological features. Our results highlight the impact of the tumor stroma on malignant progression and provide a rationale for a further exploration of components of the tumor stroma as therapeutic targets in PCa., (Copyright © 2018 Elsevier Inc. All rights reserved.)

A venous tumor thrombus (VTT) is a potentially lethal complication of renal cell carcinoma (RCC) but virtually nothing is known about the underlying natural history. Based on our observation that venous thrombi contain significant numbers of viable tumor cells, we applied multiregion whole exome sequencing to a total of 37 primary tumor and VTT samples including normal tissue specimens from five consecutive patients. Our findings demonstrate mutational heterogeneity between primary tumor and VTT with 106 of 483 genes (22%) harboring functional SNVs and/or indels altered in either primary tumor or thrombus. Reconstruction of the clonal phylogeny showed clustering of tumor samples and VTT samples, respectively, in the majority of tumors. However, no new subclones were detected suggesting that pre-existing subclones of the primary tumor drive VTT formation. Importantly, we found several lines of evidence for "BRCAness" in a subset of tumors. These included mutations in genes that confer "BRCAness", a mutational signature and an increase of small indels. Re-analysis of SNV calls from the TCGA KIRC-US cohort confirmed a high frequency of the "BRCAness" mutational signature AC3 in clear cell RCC. Our findings warrant further pre-clinical experiments and may lead to novel personalized therapies for RCC patients.

Objectives: To evaluate the safety and feasibility of sorafenib prior to surgery for downsizing tumors in patients with non-metastatic cT1-3 renal tumors together with a characterization of functional intratumoral heterogeneity (ITH)., Materials and Methods: The effects of 4-week sorafenib prior to curative surgery were assessed in a prospective, single-center, randomized, placebo-controlled, double-blinded, pilot trial in patients with T1-3N0M0 renal cell carcinoma (RCC). Patients received sorafenib or placebo for 28 days prior to surgery. MRI was performed at baseline and prior to surgery to calculate tumor volume. The clinical responses were further characterized on the molecular level by immunohistochemical stainings for Ki-67, cleaved caspase-3, and CD31., Results: After enrolling 20 patients into the study, 14 patients were randomized, of which 12 patients were available for analysis. While no significant change in tumor volume was seen for placebo (range = -24.2-0.2%) a reduction of 29.0% (range = -4.9-61.1%) was detected for sorafenib (p < 0.05). Primary renal tumor diameter changed from 10.6 cm (range = 6.5-10.8) to 10.7 cm (range = 6.7-11.1) in the placebo group, and from 5.4 cm (range = 4.3-7.3) to 4.4 cm (range = 3.5-6.8) for the sorafenib group, at baseline vs. 28 days of treatment. Correlative assessment of proliferation, apoptosis, and microvessel density revealed an enhanced degree of functional ITH in treated patients suggesting adaptive and/or regenerative processes with potential relevance for the development of drug resistance., Conclusions: Sorafenib in standard dosage, given preoperatively for 28 days, was clinically active in downsizing tumors in patients with locally confined, non-metastatic RCC together but led to an enhanced functional ITH in the residual tumor tissue.

TMPRSS2:ERG (T/E) gene fusions are present in approximately 50% of all prostate cancer (PCa) cases. The expression of fusion mRNAs from distinct T/E variants is associated with clinicopathological parameters, while the underlying molecular processes remain unclear. We characterized the molecular mechanisms and functional implications caused by doxycycline (Dox)-inducible overexpression of the frequent T/E III and VI fusion variants in LNCaP cells. Induction of T/E expression resulted in increased cellular migratory and invasive potential, and reduced proliferation and accumulation in G1 phase. T/E overexpressing cells showed epithelial-to-mesenchymal transition (EMT), as demonstrated by upregulation of TGF-β and WNT pathway genes, mesenchymal markers, and increased phosphorylation of the p38 MAPK. Augmented secretion of TGF-β1 and -β2, and T/E-mediated regulation of ALK1, a member of the TGF-β receptor family, was detected. ALK1 inhibition in T/E overexpressing cells blocked p38 phosphorylation and reduced the expression of the TGF-β target genes VIM, MMP1, CDH2, and SNAI2. We found a T/E variant VI-specific induction of miR-503 associated with reduced expression of SMAD7 and CDH1. Overexpression of miR-503 led to increased levels of VIM and MMP1. Our findings indicate that TGF-β signaling is a major determinant of EMT in T/E overexpressing LNCaP cells. We provide evidence that T/E VI-specific transcriptional modulation by miR-503 accounts for differences in the activation of EMT pathway genes, promoting the aggressive phenotype of tumors expressing T/E variant VI. We suggest that ALK1-mediated TGF-β signaling is a novel oncogenic mechanism in T/E positive PCa.

Background: Taxanes are routinely used to treat men with advanced prostate cancer, yet their molecular mode of action is poorly characterized. Taxanes stabilize microtubules and may hence interfere with a plethora of cellular processes, most notably mitosis. However, prostate cancer is typically a slowly growing tumor suggesting that additional processes play a role in the response to taxanes., Methods: Here, we analyzed the potential effect of taxanes on microtubuli-dependent intracellular transport and signaling processes, specifically, nuclear translocation of the androgen receptor and modulation of the RAS-RAF-MEK-ERK signaling cascade., Results: We show that the androgen-driven nuclear translocation of the androgen receptor remains virtually undisturbed by docetaxel in prostate cancer cells. However, we found a striking down-regulation of activated ERK1/2 together with enhanced cytotoxicity in both docetaxel or cabazitaxel-treated cells that was comparable to direct MEK kinase inhibition. Remarkably, MEK inhibition alone was less effective in inducing cytotoxicity than taxanes indicating that a down-regulation of activated ERK1/2 may be necessary but is not sufficient for taxane-induced antitumoral effects. In line with this notion, we show in a xenograft mouse model that prostate cancer cells that are resistant to docetaxel overexpress activated ERK1/2. Taken together, our findings underscore that the modulation of ERK1/2 activation, in concert with other mechanisms, plays an important role in taxane-induced antineoplastic effects on prostate cancer cells., Conclusions: These results suggest at least partially nonoverlapping effects of docetaxel and androgen deprivation therapy and hence help to understand recent clinical findings. A further elucidation of the mode of action of docetaxel would have important implications to optimize current treatment strategies and biomarker development for men with metastatic prostate cancer., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Prostate cancer is a heterogeneous disease. MiR-375 is a marker for prostate cancer progression, but its cellular function is not characterized. Here, we provide the first comprehensive investigation of miR-375 in prostate cancer. We show that miR-375 is enriched in prostate cancer compared to normal cells. Furthermore, miR-375 enhanced proliferation, migration and invasion in vitro and induced tumor growth and reduced survival in vivo showing that miR-375 has oncogenic properties in prostate cancer. On the molecular level, we provide the targetome and genome-wide transcriptional changes of miR-375 expression by applying a generalized linear model for Ago-RIP-Seq and RNA-Seq, and show that miR-375 is involved in tumorigenic networks and Polycomb regulation. Integration of tissue and gene ontology data prioritized miR-375 targets and identified the tumor suppressor gene CBX7, a member of Polycomb repressive complex 1, as a major miR-375 target. MiR-375-mediated repression of CBX7 was accompanied by increased expression of its homolog CBX8 and activated transcriptional programs linked to malignant progression in prostate cancer cells. Tissue analysis showed association of CBX7 loss with advanced prostate cancer. Our study indicates that miR-375 exerts its tumor-promoting role in prostate cancer by influencing the epigenetic regulation of transcriptional programs through its ability to directly target the Polycomb complex member CBX7.

Intratumoural heterogeneity (ITH) is a major cause of cancer-associated lethality. Extensive genomic ITH has previously been reported in clear cell renal cell carcinoma (ccRCC). Here we address the question whether ITH increases with malignant progression and can hence be exploited as a prognostic marker. Unexpectedly, precision quantitative image analysis reveals that the degree of functional ITH is virtually identical between primary ccRCCs of the lowest stage and advanced, metastatic tumours. Functional ITH was found to show a stage-independent topological pattern with peak proliferative and signalling activities almost exclusively in the tumour periphery. Exome sequencing of matching peripheral and central primary tumour specimens reveals various region-specific mutations. However, these mutations cannot directly explain the zonal pattern suggesting a role of microenvironmental factors in shaping functional ITH. In conclusion, our results indicate that ITH is an early and general characteristic of malignant growth rather than a consequence of malignant progression.

Renal cell carcinoma (RCC) is characterized by a profound disruption of proapoptotic signaling networks leading to chemo- and radioresistance. A key mediator of DNA damage-induced apoptosis is the BH3-only protein PUMA. Given its central role in proapoptotic signaling, we analyzed a series of more than 600 precision-annotated primary RCC specimens for PUMA protein expression. We found a reduced expression of PUMA in 22.6% of RCCs analyzed. Unexpectedly, however, PUMA deficiency was not associated with more aggressive tumor characteristic as expected. Instead, a reduced PUMA expression was associated with a lower TNM stage, lower histopathologic grade, and more favorable cancer-specific patient survival. A direct correlation in a separate patient cohort revealed a profound disconnection between PUMA expression and apoptosis as exemplified by the fact that the tumor with the highest level of apoptotic cells was PUMA deficient. In a series of in vitro studies, we corroborated these results and discovered the highest propensity to undergo apoptosis in an RCC cell line with virtually undetectable PUMA expression. At the same time, PUMA expression was not necessarily associated with stronger apoptosis induction, which underscores the striking functional heterogeneity of PUMA expression and apoptosis in RCC. Collectively, our findings suggest that PUMA-independent mechanisms of cell death exist and may play an important role in suppressing malignant progression. They underscore the functional heterogeneity of RCCs and suggest that PUMA expression alone may not be a suitable predictive biomarker. A better understanding of alternative proapoptotic pathways, however, may help to design novel therapeutic strategies for patients with advanced RCC., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

We have recently shown that centrosomal protein 57 (CEP57) is overexpressed in a subset of human prostate cancers. CEP57 is involved in intracellular transport processes, and its overexpression causes mitotic defects as well as abnormal microtubule nucleation and bundling. In the present study, we further characterized the prognostic and functional role of CEP57 in prostate cancer. Unexpectedly, we found that high CEP57 expression is an independent prognostic factor for a more favorable biochemical recurrence-free survival in two large patient cohorts. To reconcile this finding with the ability of CEP57 to cause cell division errors and thus potentially promote malignant progression, we hypothesized that alterations of microtubule-associated transport processes, in particular nuclear translocation of the androgen receptor (AR), may play a role in our finding. However, CEP57 overexpression and microtubule bundling had, surprisingly, no effect on the nuclear translocation of the AR. Instead, we found a significant increase of cells with disarranged microtubules and a cellular morphology suggestive of a cytokinesis defect. Because mitotic dysfunction leads to a reduced daughter cell formation, it can explain the survival benefit of patients with increased CEP57 expression. In contrast, we show that a reduced expression of CEP57 is associated with malignant growth and metastasis. Taken together, our findings underscore that high CEP57 expression is associated with mitotic impairment and less aggressive tumor behavior. Because the CEP57-induced microtubule stabilization had no detectable effect on AR nuclear translocation, our results furthermore suggest that microtubule-targeting therapeutics used in advanced prostate cancer such as docetaxel may have modes of action that are at least in part independent of AR transport inhibition., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

Resistance to DNA damage-induced apoptosis is a hallmark of cancer and a major cause of treatment failure and lethal disease outcome. A tumor entity that is largely resistant to DNA-damaging therapies including chemo- or radiotherapy is renal cell carcinoma (RCC). This study was designed to explore the underlying molecular mechanisms of DNA damage resistance in RCC to develop strategies to resensitize tumor cells to DNA damage-induced apoptosis. Here, we show that apoptosis-resistant RCC cells have a disconnect between activation of p53 and upregulation of the downstream proapoptotic protein p53 upregulated modulator of apoptosis (PUMA). We demonstrate that this disconnect is not caused by gene-specific repression through CCCTC-binding factor (CTCF) but instead by aberrant chromatin compaction. Treatment with an HDAC inhibitor was found to effectively reactivate PUMA expression on the mRNA and protein level and to revert resistance to DNA damage-induced cell death. Ectopic expression of PUMA was found to resensitize a panel of RCC cell lines to four different DNA-damaging agents tested. Remarkably, all RCC cell lines analyzed were wild-type for p53, and a knockdown was likewise able to sensitize RCC cells to acute genotoxic stress. Taken together, our results indicate that DNA damage resistance in RCC is reversible, involves the p53-PUMA axis, and is potentially targetable to improve the oncological outcomes of RCC patients., (Copyright © 2014 Neoplasia Press, Inc. Published by Elsevier Inc. All rights reserved.)

Objectives: Infection with human papillomaviruses (HPVs) is intimately associated with anogenital tract malignancies including cervical and vulvar cancer, a subset of oropharyngeal cancers and certain types of skin cancer. A number of urological tumors have likewise been suggested to be associated with high-risk HPV infection; however, many studies are hampered by a limited number of detection methods. The goal of this review article is to define a set of key criteria when implicating a virus in a human cancer and to apply these criteria to HPV infection in urological cancers., Materials and Methods: We performed a survey of the literature to corroborate the evidence to support a causal relationship between HPV infection and major urological malignancies., Results: A number of previous reports have implicated HPVs in urological malignancies including penile, prostate, and bladder cancer. Most reports, however, rely only on a limited number of detection methods and frequently use contamination-prone polymerase chain reaction based methods. To firmly establish a link between a viral infection and a human malignancy, it is paramount that an array of techniques is employed and that the virus is ultimately traced by either direct visualization or, in the case of viral genome that has integrated into the host genome, detection of viral genes and gene products as well as functional cellular perturbations. In any case, seroepidemiological studies are likewise crucial to support the evidence. Such evidence for a role of HPV in urological malignancies based on currently available techniques is only present for penile squamous cell carcinomas., Conclusions: An increasing number of immunocompromised patients as well as novel developments in patient care may change the spectrum of HPV-associated neoplasms. This is examplified by results demonstrating a role of HPVs in rare urothelial carcinomas with squamous differentiation in patients with neurogenic bladder. Hence, it is important to keep HPV infection in mind when confronted with unusual disease manifestations of the urogenital tract., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Malignant tumors with deregulated FGF-2 expression such as prostate cancer are also frequently aneuploid. Aneuploidy can be caused by cell division errors due to extra centrosomes and mitotic spindle poles. However, a link between FGF-2 overexpression and chromosome missegregation has so far been elusive. Here, we show that FGF-2 rapidly uncouples centrosome duplication from the cell division cycle in prostate cancer cells through CEP57, an intracellular FGF-2-binding and trafficking factor. CEP57 was initially identified as a regulator of centriole overduplication in an RNA interference screen. We subsequently found that CEP57 rapidly stimulates centriole overduplication and mitotic defects when overexpressed and is required not only for FGF-2-induced centriole overduplication but also for normal centriole duplication. We provide evidence that CEP57 functions by modulating tubulin acetylation, thereby promoting daughter centriole stability. CEP57 was found to be overexpressed on the mRNA and protein level in a subset of prostate cancers, of which the vast majority also showed FGF-2 upregulation. Taken together, our results show an unexpected link between altered microenvironmental signaling cues such as FGF-2 overexpression and mitotic instability and provide a rationale for the therapeutic targeting of the FGF-2/FGFR1/CEP57 axis in prostate cancer. Cancer Res; 73(4); 1400-10. ©2012 AACR.

Merkel cell polyomavirus (MCV) causes ~80% of primary and metastatic Merkel cell carcinomas (MCCs). By comparing digital transcriptome subtraction deep-sequencing profiles, we found that transcripts of the cellular survivin oncoprotein [BIRC5a (baculoviral inhibitor of apoptosis repeat-containing 5)] were up-regulated sevenfold in virus-positive compared to virus-negative MCC tumors. Knockdown of MCV large T antigen in MCV-positive MCC cell lines decreased survivin mRNA and protein expression. Exogenously expressed MCV large T antigen increased survivin protein expression in non-MCC primary cells. This required an intact retinoblastoma protein-targeting domain that activated survivin gene transcription as well as expression of other G(1)-S-phase proteins including E2F1 and cyclin E. Survivin expression is critical to the survival of MCV-positive MCC cells. A small-molecule survivin inhibitor, YM155, potently and selectively initiates irreversible, nonapoptotic, programmed MCV-positive MCC cell death. Of 1360 other chemotherapeutic and pharmacologically active compounds screened in vitro, only bortezomib (Velcade) was found to be similarly potent, but was not selective in killing MCV-positive MCC cells. YM155 halted the growth of MCV-positive MCC xenograft tumors and was nontoxic in mice, whereas bortezomib was not active in vivo and mice displayed serious morbidity. Xenograft tumors resumed growth once YM155 treatment was stopped, suggesting that YM155 may be cytostatic rather than cytotoxic in vivo. Identifying the cellular pathways, such as those involving survivin, that are targeted by tumor viruses can lead to rapid and rational identification of drug candidates for treating virus-induced cancers.

Merkel cell polyomavirus (MCV) is a recently discovered human virus closely related to African green monkey lymphotropic polyomavirus. MCV DNA is integrated in approximately 80% of Merkel cell carcinomas (MCC), a neuroendocrine skin cancer linked to lymphoid malignancies such as chronic lymphocytic leukemia (CLL). To assess MCV infection and its association with human diseases, we developed a monoclonal antibody that specifically recognizes endogenous and transfected MCV large T (LT) antigen. We show expression of MCV LT protein localized to nuclei of tumor cells from MCC having PCR quantified MCV genome at an average of 5.2 (range 0.8-14.3) T antigen DNA copies per cell. Expression of this putative viral oncoprotein in tumor cells provides the mechanistic underpinning supporting the notion that MCV causes a subset of MCC. In contrast, although 2.2% of 325 hematolymphoid malignancies surveyed also showed evidence for MCV infection by DNA PCR, none were positive at high viral copy numbers, and none of 173 lymphoid malignancies examined on tissue microarrays expressed MCV LT protein in tumor cells. As with some of the other human polyomaviruses, lymphocytes may serve as a tissue reservoir for MCV infection, but hematolymphoid malignancies associated with MCC are unlikely to be caused by MCV., (2009 UICC)

Aims: Home-made preparation of heroin is common in countries of the former Soviet Union (FSU), and the addition of blood during its preparation and the use of contaminated syringes to distribute it may play a role in the rapid spread of HIV-1 among injecting drug users (IDUs). This study was designed to determine the viability of HIV-1 during these procedures., Setting: Field observations of home-made opiate manufacture in four FSU countries were used to develop a consensus protocol to replicate manufacture in the laboratory that included the addition of human blood contaminated with HIV-1., Design and Measurement: Following the addition of HIV-1-contaminated blood during manufacture or storage, we attempted to recover viable HIV-1. The recovery was measured by propagation of the virus in stimulated white blood cells from uninfected donors., Findings: In experiments in which HIV-1 contaminated blood was added during manufacture, no viable HIV-1 was recovered. In experiments in which chornaya was introduced into HIV-contaminated syringes, the percentage of syringes containing viable HIV-1 was reduced. The reduction appeared to be related to the interaction of HIV-1 contaminated blood with a component of the poppies. While HIV-contaminated syringes used to dispense or inject home-made opiates might transmit HIV, the ability of chornaya to reduce HIV viability seems to make this route of transmission less efficient., Conclusions: The epidemic of HIV-1 among IDUs in the FSU resulted more probably from recognized injection risk behaviors-including sharing syringes and drug solutions--than from opiate solutions harboring viable HIV-1.

Bleaching of syringes has been advocated to prevent HIV transmission among injection drug users (IDUs). Several reports indicate that IDUs use household products to disinfect syringes instead of bleach. To test their disinfection efficacy, we performed syringe-rinsing simulations with a range of agents used by IDUs trying to disinfect their syringes. No viable HIV-1 was recovered from syringes rinsed with bleach diluted 1:10. Bleach stored at 37 degrees C and rubbing alcohol performed better than water and the other liquids tested, but less well than bleach 1:10. Rinsing syringes with the other liquids was similar to rinsing with water alone. Increasing the rinsing volume did not always increase the effect of rinsing, but the addition of a second rinse consistently increased rinsing efficacy. Bleaching remains the most effective disinfectant among those tested. It is important that IDUs learn the proper techniques for bleach storage and syringe decontamination. Other household products are not effective disinfectants and should be avoided. Because access to sterile syringes may be restricted by laws, public policy, and police practices, bleach retains its importance in the control of the HIV-1 epidemic among IDUs.