Metastatic Undifferentiated Melanoma Mimicking a Primary Bone Tumor: A Potential Diagnostic Pitfall.

ABSTRACT: Undifferentiated melanoma (UM) is defined by the loss of classic morphologic and immunohistochemical melanocytic markers. Reports in the literature are rare and show that UM usually occurs as a metastasis in the setting of a known primary cutaneous melanoma. The most common mutations in UM include those involving BRAF , NRAS , and KIT , which are almost invariably present in the parent melanoma. In this study, we report a case of a primary sinonasal melanoma with metastatic UM presenting with osteoclast-like giant cells and resembling a primary bone tumor. The retention of an unusual KRAS mutation in UM that was also present in the primary lesion provided critical information for the diagnosis. Our report highlights the importance of considering mutational analysis to identify undifferentiated melanomas in patients with metastatic tumors which do not have the typical histopathologic and immunohistochemical features of melanoma.

Comprehensive molecular characterization of adenoid cystic carcinoma reveals tumor suppressors as novel drivers and prognostic biomarkers.

Adenoid cystic carcinoma (ACC) is a MYB-driven head and neck malignancy with high rates of local recurrence and distant metastasis and poor long-term survival. New effective targeted therapies and clinically useful biomarkers for patient stratification are needed to improve ACC patient survival. Here, we present an integrated copy number and transcriptomic analysis of ACC to identify novel driver genes and prognostic biomarkers. A total of 598 ACCs were studied. Clinical follow-up was available from 366 patients, the largest cohort analyzed to date. Copy number losses of 1p36 (70/492; 14%) and of the tumor suppressor gene PARK2 (6q26) (85/343; 25%) were prognostic biomarkers; patients with concurrent losses (n = 20) had significantly shorter overall survival (OS) than those with one or no deletions (p < 0.0001). Deletion of 1p36 independently predicted short OS in multivariate analysis (p = 0.02). Two pro-apoptotic genes, TP73 and KIF1B, were identified as putative 1p36 tumor suppressor genes whose reduced expression was associated with poor survival and increased resistance to apoptosis. PARK2 expression was markedly reduced in tumors with 6q deletions, and PARK2 knockdown increased spherogenesis and decreased apoptosis, indicating that PARK2 is a tumor suppressor in ACC. Moreover, analysis of the global gene expression pattern in 30 ACCs revealed a transcriptomic signature associated with short OS, multiple copy number alterations including 1p36 deletions, and reduced expression of TP73. Taken together, the results indicate that TP73 and PARK2 are novel putative tumor suppressor genes and potential prognostic biomarkers in ACC. Our studies provide new important insights into the pathogenesis of ACC. The results have important implications for biomarker-driven stratification of patients in clinical trials. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Rearrangements, Expression, and Clinical Significance of MYB and MYBL1 in Adenoid Cystic Carcinoma: A Multi-Institutional Study.

Adenoid cystic carcinoma (ACC) is an aggressive head and neck malignancy characterized by a t (6;9) translocation resulting in an MYB-NFIB gene fusion or, more rarely, an MYBL1 fusion. The true frequency and clinical significance of these alterations are still unclear. Here, we have used tissue microarrays and analyzed 391 ACCs and 647 non-ACC salivary neoplasms to study the prevalence, expression, and clinical significance of MYB/MYBL1 alterations by FISH and immunohistochemistry. Alterations of MYB or MYBL1 were found in 78% of the cases, of which 62% had MYB alterations and 16% had MYBL1 rearrangements. Overexpression of MYB/MYBL1 oncoproteins was detected in 93% of the cases. MYB split signal, seen in 39% of the cases, was specific for ACC and not encountered in non-ACC salivary tumors. Loss of the 3'-part of MYB was enriched in grade 3 tumors and was a significant independent prognostic biomarker for overall survival in multivariate analyses. We hypothesize that loss of the 3'-part of MYB results from an unbalanced t(6;9) leading to an MYB-NFIB fusion with concomitant loss of the segment distal to the MYB breakpoint in 6q23.3. Our study provides new knowledge about the prevalence and clinical significance of MYB/MYBL1 alterations and indicates the presence of genes with tumor suppressive functions in 6q23.3-qter that contribute to poor prognosis and short overall survival in ACC.

Global Health Education in Pathology Residency.

OBJECTIVES: Pathology and laboratory medicine (PALM) services in low- and middle-income countries are essential to combat the increasing prevalence of cancer in addition to providing documentation of cancer types and trends for future allocation of public health resources. There are many ways PALM as a whole can engage on the global health front. This study summarizes the efforts and results of a global health educational and clinical elective for pathology residents in Quetzaltenango, Guatemala. METHODS: Pathology residents led and implemented the project, working alongside an in-country pathologist and project collaborator to instill project sustainability and allow for future capacity building. RESULTS: An educational elective was established between the pathology departments of the University of Virginia and Hospital Regional de Occidente in Quetzaltenango, Guatemala. Two residents at a time engaged in a month-long educational elective assisting and learning from the in-country pathologist in anatomic pathology clinical work. CONCLUSIONS: The project is an example of a global health initiative centering on the enhancement of PALM services in a low-resource environment via a bidirectional, sustainable educational exchange.

Post-Transcriptional Regulation of PARP7 Protein Stability Is Controlled by Androgen Signaling.

Poly-ADP-ribose polymerases (PARPs) are enzymes that catalyze ADP-ribosylation and play critical roles in normal and disease settings. The PARP family member, PARP7, is a mono-ADP-ribosyltransferase that has been suggested to play a tumor suppressive role in breast, ovarian, and colorectal cancer. Here, we have investigated how androgen signaling regulates PARP7 homeostasis in prostate cancer cells, where PARP7 is a direct target gene of AR. We found that the PARP7 protein is extremely short-lived, with a half-life of 4.5 min. We show that in addition to its transcriptional regulation by AR, PARP7 is subject to androgen-dependent post-transcriptional regulation that increases its half-life to 25.6 min. This contrasts with PARP1, PARP2, PARP9, and PARP14, which do not display rapid turnover and are not regulated by androgen signaling. Androgen- and AR-dependent stabilization of PARP7 leads to accumulation in the nucleus, which we suggest is a major site of action. Mutations in the catalytic domain, the Cys3His1 zinc finger, and WWE (tryptophan-tryptophan-glutamate) domains in PARP7 each reduce the degradation rate of PARP7, suggesting the overall structure of the protein is tuned for its rapid turnover. Our finding that PARP7 is regulated by AR signaling both transcriptionally and post-transcriptionally in prostate cancer cells suggests the dosage of PARP7 protein is subject to tight regulation.

Cytodiagnosis and protein typing of amyloid from a vitreous washing: initial diagnostic workup of hereditary amyloidosis.

Hereditary amyloidosis is a challenging but critical diagnosis, with serious implications with regard to treatment and disease surveillance for both patients and their families. Systemic symptomology is often vague. As vitreous amyloid deposition is strongly linked to the systemic, hereditary disease, its cytodiagnosis in the vitreous may be the incipient finding of hereditary amyloidosis. We describe a 64-year-old man with a history of heart disease and peripheral neuropathy who presented with asymmetric visual disturbances and vitreous opacities, leading to diagnostic vitrectomy. Amyloid was identified on a ThinPrep slide of the vitreous sample via Congo red stain. Creation of a cell block from the residual ThinPrep sample allowed for amyloid protein typing, identifying ATTR (transthyretin)-type amyloid and strongly suggesting hereditary amyloidosis. Subsequent sequencing of the patient's TTR gene identified a pathogenic variant that is associated with autosomal dominant hereditary transthyretin-mediated amyloidosis.

Klf5 acetylation regulates luminal differentiation of basal progenitors in prostate development and regeneration.

Prostate development depends on balanced cell proliferation and differentiation, and acetylated KLF5 is known to alter epithelial proliferation. It remains elusive whether post-translational modifications of transcription factors can differentially determine adult stem/progenitor cell fate. Here we report that, in human and mouse prostates, Klf5 is expressed in both basal and luminal cells, with basal cells preferentially expressing acetylated Klf5. Functionally, Klf5 is indispensable for maintaining basal progenitors, their luminal differentiation, and the proliferation of their basal and luminal progenies. Acetylated Klf5 is also essential for basal progenitors' maintenance and proper luminal differentiation, as deacetylation of Klf5 causes excess basal-to-luminal differentiation; attenuates androgen-mediated organoid organization; and retards postnatal prostate development. In basal progenitor-derived luminal cells, Klf5 deacetylation increases their proliferation and attenuates their survival and regeneration following castration and subsequent androgen restoration. Mechanistically, Klf5 deacetylation activates Notch signaling. Klf5 and its acetylation thus contribute to postnatal prostate development and regeneration by controlling basal progenitor cell fate.

Antitumor effect of insulin-like growth factor-1 receptor inhibition in head and neck squamous cell carcinoma.

OBJECTIVES: The insulin-like growth factor-1 receptor (IGF1R) has been implicated in therapeutic resistance in head and neck squamous cell carcinoma (HNSCC), and small molecule tyrosine kinase inhibitors (TKIs) of IGF1R activity may have anticancer activity. Therefore, the relationship between survival and IGF1R expression was assessed for oral cavity (OC) cancer, and the antitumor effects of two IGF1R-TKIs, OSI-906 and BMS-754807, were evaluated in HNSCC cell lines in vitro. METHODS: Clinical outcome data and tissue microarray immunohistochemistry were used to generate IGF1R expression-specific survival curves. Immunoblot, alamarBlue proliferation assay, trypan blue exclusion viability test, clonogenic assay, flow cytometry, and reverse phase protein array (RPPA) were used to evaluate in vitro responses to IGF1R-TKIs. RESULTS: For patients with stage III/IV OCSCC, higher IGF1R expression was associated with poorer overall 5-year survival (P = 0.029). Both BMS-754807 and OSI-906 caused dose-dependent inhibition of IGF1R and Akt phosphorylation and inhibited proliferation; BMS-754807 was more potent than OSI-906. Both drugs reduced HNSCC cell viability; only OSI-906 was able to eliminate all viable cells at 10 µM. The two drugs similarly inhibited clonogenic cell survival. At 1 µM, only BMS-754807 caused a fourfold increase in the basal apoptotic rate. RPPA demonstrated broad effects of both drugs on canonical IGF1R signaling pathways and also inhibition of human epidermal growth factor receptor-3 (HER3), Src, paxillin, and ezrin phosphorylation. CONCLUSION: OSI-906 and BMS-754807 inhibit IGF1R activity in HNSCC cell lines with reduction in prosurvival and proliferative signaling and with concomitant antiproliferative and proapoptotic effects. Such antagonists may have utility as adjuvants to existing therapies for HNSCC. LEVEL OF EVIDENCE: NA Laryngoscope, 130:1470-1478, 2020.

Discovery of a novel long noncoding RNA overlapping the LCK gene that regulates prostate cancer cell growth.

BACKGROUND: Virtually all patients with metastatic prostate cancer (PCa) will relapse and develop lethal castration-resistant prostate cancer (CRPC). Long noncoding RNAs (lncRNAs) are emerging as critical regulatory elements of many cellular biological processes, and may serve as therapeutic targets for combating PCa progression. Here, we have discovered in a high-throughput RNAi screen a novel lncRNA in PCa, and assessed the oncogenic effects of this lncRNA. METHODS: Rapid amplification of cDNA ends and sequencing was utilized to identify a previously unannotated lncRNA lying within exon six and the 3'UTR of the lymphocyte-specific protein tyrosine kinase (LCK) gene. The levels of HULLK in the presence or absence of hormone and/or enzalutamide or coregulator inhibitors were measured by quantitative PCR (qPCR). The determination of HULLK transcription and localization were characterized by strand-specific qPCR and cellular fractionation followed by qPCR, respectively. The correlation between HULLK expression and prostate cancer Gleason score was analyzed by droplet digital PCR. CyQuant assays were conducted to evaluate the effects of knocking down HULLK with shRNAs or overexpressing HULLK on cell growth. RESULTS: In this study, a previously unannotated lncRNA lying within exon six and 3'UTR of the LCK gene was dramatically upregulated by androgen in a dose-dependent manner, and the anti-androgen enzalutamide completely blocked this hormone-induced increase. Therefore, we labeled this lncRNA "HULLK" for Hormone-Upregulated lncRNA within LCK. Binding sites for two AR coregulators p300 and Brd4 reside near the HULLK transcriptional start site (TSS), and inhibitors of these coregulators downregulated HULLK. HULLK is transcribed from the sense strand of DNA, and predominantly localizes to the cytoplasm. HULLK transcripts are not only expressed in prostate cancer cell lines, but also prostate cancer patient tissue. Remarkably, there was a significant positive correlation between HULLK expression and high-grade PCa in multiple cohorts. shRNAs targeting HULLK significantly decreased PCa cell growth. Moreover, cells overexpressing HULLK were hypersensitive to androgen stimulation. CONCLUSIONS: HULLK is a novel lncRNA situated within the LCK gene that may serve as an oncogene in PCa. Our data enhances our understanding of lncRNA biology and may assist in the development of additional biomarkers or more effective therapeutic targets for advanced PCa.

TGIF transcription factors repress acetyl CoA metabolic gene expression and promote intestinal tumor growth.

Tgif1 (thymine-guanine-interacting factor 1) and Tgif2 repress gene expression by binding directly to DNA or interacting with transforming growth factor (TGF) ß-responsive SMADs. Tgifs are essential for embryogenesis and may function in tumor progression. By analyzing both gain and loss of Tgif function in a well-established mouse model of intestinal cancer, we show that Tgifs promote adenoma growth in the context of mutant Apc (adenomatous polyposis coli). Despite the tumor-suppressive role of TGFß signaling, transcriptome profiling of colon tumors suggests minimal effect of Tgifs on the TGFß pathway. Instead, it appears that Tgifs, which are up-regulated in Apc mutant colon tumors, contribute to reprogramming metabolic gene expression. Integrating gene expression data from colon tumors with other gene expression and chromatin-binding data identifies a set of direct Tgif target genes encoding proteins involved in acetyl CoA and pyruvate metabolism. Analysis of both tumor and nontumor tissues indicates that these genes are targets of Tgif repression in multiple settings, suggesting that this is a core Tgif function. We propose that Tgifs play an important role in regulating basic energy metabolism in normal cells, and that this function of Tgifs is amplified in some cancers.

Elucidating the role of Agl in bladder carcinogenesis by generation and characterization of genetically engineered mice.

Amylo-α-1,6-glucosidase,4-α-glucanotransferase (AGL) is an enzyme primarily responsible for glycogen debranching. Germline mutations lead to glycogen storage disease type III (GSDIII). We recently found AGL to be a tumor suppressor in xenograft models of human bladder cancer (BC) and low levels of AGL expression in BC are associated with poor patient prognosis. However, the impact of low AGL expression on the susceptibility of normal bladder to carcinogenesis is unknown. We address this gap by developing a germline Agl knockout (Agl-/-) mouse that recapitulates biochemical and histological features of GSDIII. Agl-/- mice exposed to N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) had a higher BC incidence compared with wild-type mice (Agl+/+). To determine if the increased BC incidence observed was due to decreased Agl expression in the urothelium specifically, we developed a urothelium-specific conditional Agl knockout (Aglcko) mouse using a Uroplakin II-Cre allele. BBN-induced carcinogenesis experiments repeated in Aglcko mice revealed that Aglcko mice had a higher BC incidence than control (Aglfl/fl) mice. RNA sequencing revealed that tumors from Agl-/- mice had 19 differentially expressed genes compared with control mice. An 'Agl Loss' gene signature was developed and found to successfully stratify normal and tumor samples in two BC patient datasets. These results support the role of AGL loss in promoting carcinogenesis and provide a rationale for evaluating Agl expression levels, or Agl Loss gene signature scores, in normal urothelium of populations at risk of BC development such as older male smokers.

PD-L1 expression in tumor cells and the immunologic milieu of bladder carcinomas: a pathologic review of 165 cases.

Programmed death ligand 1 (PD-L1) is a transmembrane protein that plays a major role in immune suppression. Its interaction with the receptor PD-1 results in downregulation of antitumoral immunity. Humanized monoclonal antibodies that interrupt the PD-L1/PD-1 interaction have shown therapeutic efficacy in patients with advanced urothelial cancer. However, immunohistochemical staining of PD-L1 in bladder tumors and its relationship to tumor histologic type, grade, and overall survival has been incompletely analyzed. Slides from 165 cystectomy specimens were reviewed for tumor type, grade of urothelial carcinoma, pathologic stage, and overall survival. A tissue microarray (TMA) using four 0.6 mm cores from each case was constructed. Immunohistochemistry was performed on the TMA using a variety of new PD-L1 antibodies and platforms now widely available. For each case, the percent of tumor cells positive for PD-L1 and the percent of positive immune cells were scored. The overall number of bladder cancers positive for PD-L1 depended on the antibody/platform combination used and the threshold for considering a tumor "PD-L1-positive." Squamous cell carcinomas (SCCs) of the bladder demonstrated PD-L1 positivity more frequently than urothelial cell carcinomas (UCCs). High-grade UCCs were positive for PD-L1 on tumor cells more frequently than low-grade UCCs. There was no difference in survival between PD-L1-positive and PD-L1-negative bladder cancers in our study. Further studies should consider examining the predictive significance of PD-L1 IHC in bladder cancers.

TGFß signaling limits lineage plasticity in prostate cancer.

Although treatment options for localized prostate cancer (CaP) are initially effective, the five-year survival for metastatic CaP is below 30%. Mutation or deletion of the PTEN tumor suppressor is a frequent event in metastatic CaP, and inactivation of the transforming growth factor (TGF) ß signaling pathway is associated with more advanced disease. We previously demonstrated that mouse models of CaP based on inactivation of Pten and the TGFß type II receptor (Tgfbr2) rapidly become invasive and metastatic. Here we show that mouse prostate tumors lacking Pten and Tgfbr2 have higher expression of stem cell markers and genes indicative of basal epithelial cells, and that basal cell proliferation is increased compared to Pten mutants. To better model the primarily luminal phenotype of human CaP we mutated Pten and Tgfbr2 specifically in luminal cells, and found that these tumors also progress to invasive and metastatic cancer. Accompanying the transition to invasive cancer we observed de-differentiation of luminal tumor cells to an intermediate cell type with both basal and luminal markers, as well as differentiation to basal cells. Proliferation rates in these de-differentiated cells were lower than in either basal or luminal cells. However, de-differentiated cells account for the majority of cells in micro-metastases consistent with a preferential contribution to metastasis. We suggest that active TGFß signaling limits lineage plasticity in prostate luminal cells, and that de-differentiation of luminal tumor cells can drive progression to metastatic disease.

The protein kinase C super-family member PKN is regulated by mTOR and influences differentiation during prostate cancer progression.

BACKGROUND: Phosphoinositide-3 (PI-3) kinase signaling has a pervasive role in cancer. One of the key effectors of PI-3 kinase signaling is AKT, a kinase that promotes growth and survival in a variety of cancers. Genetically engineered mouse models of prostate cancer have shown that AKT signaling is sufficient to induce prostatic epithelial neoplasia (PIN), but insufficient for progression to adenocarcinoma. This contrasts with the phenotype of mice with prostate-specific deletion of Pten, where excessive PI-3 kinase signaling induces both PIN and locally invasive carcinoma. We reasoned that additional PI-3 kinase effector kinases promote prostate cancer progression via activities that provide biological complementarity to AKT. We focused on the PKN kinase family members, which undergo activation in response to PI-3 kinase signaling, show expression changes in prostate cancer, and contribute to cell motility pathways in cancer cells. METHODS: PKN kinase activity was measured by incorporation of 32 P into protein substrates. Phosphorylation of the turn-motif (TM) in PKN proteins by mTOR was analyzed using the TORC2-specific inhibitor torin and a PKN1 phospho-TM-specific antibody. Amino acid substitutions in the TM of PKN were engineered and assayed for effects on kinase activity. Cell motility-related functions and PKN localization was analyzed by depletion approaches and immunofluorescence microscopy, respectively. The contribution of PKN proteins to prostate tumorigenesis was characterized in several mouse models that express PKN transgenes. The requirement for PKN activity in prostate cancer initiated by loss of phosphatase and tensin homolog deleted on chromosome 10 (Pten), and the potential redundancy between PKN isoforms, was analyzed by prostate-specific deletion of Pkn1, Pkn2, and Pten. RESULTS AND CONCLUSIONS: PKN1 and PKN2 contribute to motility pathways in human prostate cancer cells. PKN1 and PKN2 kinase activity is regulated by TORC2-dependent phosphorylation of the TM, which together with published data indicates that PKN proteins receive multiple PI-3 kinase-dependent inputs. Transgenic expression of active AKT and PKN1 is not sufficient for progression beyond PIN. Moreover, Pkn1 is not required for tumorigenesis initiated by loss of Pten. Triple knockout of Pten, Pkn1, and Pkn2 in mouse prostate results in squamous cell carcinoma, an uncommon but therapy-resistant form of prostate cancer.

Fine Needle Aspiration Cytology of Diffuse-Type Tenosynovial Giant Cell Tumors.

BACKGROUND: Tenosynovial giant cell tumor (TSGCT), also known as giant cell tumor of tendon sheath or pigmented villonodular synovitis, is the most common benign tumor of the tendon and synovium. The intra-articular diffuse type can present as a large infiltrative mass involving adjacent soft tissue and sometimes causes secondary destruction of bone, which leads to radiographic and clinical concern for malignancy. The tumor may also be purely extra-articular. CASE: Here, we report the fine needle aspiration cytology findings of 2 cases of diffuse-type TSGCT with large mononuclear cells with eccentric nuclei, finely granular cytoplasm, and a peripheral well-defined cytoplasmic rim of hemosiderin ("ladybird cells"). CONCLUSION: Although the presence of ladybird cells has been described in tissue sections of TSGCT, their identification in cytological specimens has not been reported to our knowledge. When observed, their presence may aid in differentiating TSGCT from other lesions with multinucleated osteoclast-type giant cells occurring at or near joints.

Recurrent cis-SAGe chimeric RNA, D2HGDH-GAL3ST2, in prostate cancer.

Neighboring genes transcribing in the same direction can form chimeric RNAs via cis-splicing (cis-SAGe). Previously, we reported 16 novel cis-SAGe chimeras in prostate cancer cell lines, and performed in silico validation on 14 pairs of normal and tumor samples from Chinese patients. However, whether these fusions exist in different populations, as well as their clinical implications, remains unclear. To investigate, we developed a bioinformatics pipeline using modified Spliced Transcripts Alignment to a Reference (STAR) to quantify these fusion RNAs simultaneously in silico. From RNA-Seq data of 100 paired normal and prostate cancer samples from TCGA, we find that most fusions are not specific to cancer. However, D2HGDH-GAL3ST2 is more frequently seen in cancer samples, and seems to be enriched in the African American group. Further validation with our own collection as well as from commercial sources did not detect this fusion RNA in 29 normal prostate samples, but in 19 of 93 prostate cancer samples. It is more frequently detected in late stage cancer, suggesting a role in cancer progression. Consistently, silencing this fusion resulted in dramatic reduction of cell proliferation rate and cell motility.

Role of CTCF in Regulating SLC45A3-ELK4 Chimeric RNA.

The chimeric RNA, SLC45A3-ELK4, was found to be a product of cis-splicing between the two adjacent genes (cis-SAGe). Despite the biological and clinical significance of SLC45A3-ELK4, its generating mechanism has not been elucidated. It was shown in one cell line that the binding of transcription factor CTCF to the insulators located at or near the gene boundaries, inversely correlates with the level of the chimera. To investigate the mechanism of such cis-SAGe events, we sequenced potential regions that may play a role in such transcriptional read-through. We could not detect mutations at the transcription termination site, insulator sites, splicing sites, or within CTCF itself in LNCaP cells, thus suggesting a "soft-wired" mechanism in regulating the cis-SAGe event. To investigate the role CTCF plays in regulating the chimeric RNA expression, we compared the levels of CTCF binding to the insulators in different cell lines, as well as clinical samples. Surprisingly, we did not find an inverse correlation between CTCF level, or its bindings to the insulators and SLC45A3-ELK4 expression among different samples. However, in three prostate cancer cell lines, different environmental factors can cause the expression levels of the chimeric RNA to change, and these changes do inversely correlate with CTCF level, and/or its bindings to the insulators. We thus conclude that CTCF and its bindings to the insulators are not the primary reasons for differential SLC45A3-ELK4 expression in different cell lines, or clinical cases. However, they are the likely mechanism for the same cells to respond to different environmental cues, in order to regulate the expression of SLC45A3-ELK4 chimeric RNA. This response to different environmental cues is not general to other cis-SAGe events, as we only found one out of 16 newly identified chimeric RNAs showing a pattern similar to SLC45A3-ELK4.

Checkpoint Kinase 2 Negatively Regulates Androgen Sensitivity and Prostate Cancer Cell Growth.

Prostate cancer is the second leading cause of cancer death in American men, and curing metastatic disease remains a significant challenge. Nearly all patients with disseminated prostate cancer initially respond to androgen deprivation therapy (ADT), but virtually all patients will relapse and develop incurable castration-resistant prostate cancer (CRPC). A high-throughput RNAi screen to identify signaling pathways regulating prostate cancer cell growth led to our discovery that checkpoint kinase 2 (CHK2) knockdown dramatically increased prostate cancer growth and hypersensitized cells to low androgen levels. Mechanistic investigations revealed that the effects of CHK2 were dependent on the downstream signaling proteins CDC25C and CDK1. Moreover, CHK2 depletion increased androgen receptor (AR) transcriptional activity on androgen-regulated genes, substantiating the finding that CHK2 affects prostate cancer proliferation, partly, through the AR. Remarkably, we further show that CHK2 is a novel AR-repressed gene, suggestive of a negative feedback loop between CHK2 and AR. In addition, we provide evidence that CHK2 physically associates with the AR and that cell-cycle inhibition increased this association. Finally, IHC analysis of CHK2 in prostate cancer patient samples demonstrated a decrease in CHK2 expression in high-grade tumors. In conclusion, we propose that CHK2 is a negative regulator of androgen sensitivity and prostate cancer growth, and that CHK2 signaling is lost during prostate cancer progression to castration resistance. Thus, perturbing CHK2 signaling may offer a new therapeutic approach for sensitizing CRPC to ADT and radiation.

Additive Effect of Zfhx3/Atbf1 and Pten Deletion on Mouse Prostatic Tumorigenesis.

The phosphatase and tensin homolog (PTEN) and the zinc finger homeobox 3 (ZFHX3)/AT-motif binding factor 1 (ATBF1) genes have been established as tumor suppressor genes in prostate cancer by their frequent deletions and mutations in human prostate cancer and by the formation of mouse prostatic intraepithelial neoplasia (mPIN) or tumor by their deletions in mouse prostates. However, whether ZFHX3/ATBF1 deletion together with PTEN deletion facilitates prostatic tumorigenesis is unknown. In this study, we simultaneously deleted both genes in mouse prostatic epithelia and performed histological and molecular analyses. While deletion of one Pten allele alone caused low-grade (LG) mPIN as previously reported, concurrent deletion of Zfhx3/Atbf1 promoted the progression to high-grade (HG) mPIN or early carcinoma. Zfhx3/Atbf1 and Pten deletions together increased cell proliferation, disrupted the smooth muscle layer between epithelium and stroma, and increased the number of apoptotic cells. Deletion of both genes also accelerated the activation of Akt and Erk1/2 oncoproteins. These results suggest an additive effect of ZFHX3/ATBF1 and PTEN deletions on the development and progression of prostate neoplasia.