p53R172H and p53R245W Hotspot Mutations Drive Distinct Transcriptomes in Mouse Mammary Tumors Through a Convergent Transcriptional Mediator.

Aggressive breast cancers harbor TP53 missense mutations. Tumor cells with TP53 missense mutations exhibit enhanced growth and survival through transcriptional rewiring. To delineate how TP53 mutations in breast cancer contribute to tumorigenesis and progression in vivo, we created a somatic mouse model driven by mammary epithelial cell-specific expression of Trp53 mutations. Mice developed primary mammary tumors reflecting the human molecular subtypes of Luminal A, Luminal B, HER2-enriched, and Triple Negative Breast Cancer with metastases. Transcriptomic analyses comparing MaPR172H/- or MaPR245W/- mammary tumors to MaP-/- tumors revealed (1) differences in cancer associated pathways activated in both p53 mutants and (2) Nr5a2 as a novel transcriptional mediator of distinct pathways in p53 mutants. Meta-analyses of human breast tumors corroborated these results. In vitro assays demonstrate mutant p53 upregulates specific target genes that are enriched for Nr5a2 response elements in their promoters. Co-immunoprecipitation studies revealed p53R172H and p53R245W interact with Nr5a2. These findings implicate NR5A2 as a novel mediator of mutant p53 transcriptional activity in breast cancer.

Genome-wide CRISPR-Cas9 screen analyzed by SLIDER identifies network of repressor complexes that regulate TRIM24.

TRIM24 is an oncogenic chromatin reader that is frequently overexpressed in human tumors and associated with poor prognosis. However, TRIM24 is rarely mutated, duplicated, or rearranged in cancer. This raises questions about how TRIM24 is regulated and what changes in its regulation are responsible for its overexpression. Here, we perform a genome-wide CRISPR-Cas9 screen by fluorescence-activated cell sorting (FACS) that nominated 220 negative regulators and elucidated a regulatory network that includes the KAP1 corepressor, CNOT deadenylase, and GID/CTLH E3 ligase. Knocking out required components of these three complexes caused TRIM24 overexpression, confirming their negative regulation of TRIM24. Our findings identify regulators of TRIM24 that nominate previously unexplored contexts for this oncoprotein in biology and disease. These findings were enabled by SLIDER, a new scoring system designed and vetted in our study as a broadly applicable tool for analysis of CRISPR screens performed by FACS.

Unique Transcriptional Profiles Underlie Osteosarcomagenesis Driven by Different p53 Mutants.

Missense mutations in the DNA binding domain of p53 are characterized as structural or contact mutations based on their effect on the conformation of the protein. These mutations show gain-of-function (GOF) activities, such as promoting increased metastatic incidence compared with p53 loss, often mediated by the interaction of mutant p53 with a set of transcription factors. These interactions are largely context specific. To understand the mechanisms by which p53 DNA binding domain mutations drive osteosarcoma progression, we created mouse models, in which either the p53 structural mutant p53R172H or the contact mutant p53R245W are expressed specifically in osteoblasts, yielding osteosarcoma tumor development. Survival significantly decreased and metastatic incidence increased in mice expressing p53 mutants compared with p53-null mice, suggesting GOF. RNA sequencing of primary osteosarcomas revealed vastly different gene expression profiles between tumors expressing the missense mutants and p53-null tumors. Further, p53R172H and p53R245W each regulated unique transcriptomes and pathways through interactions with a distinct repertoire of transcription factors. Validation assays showed that p53R245W, but not p53R172H, interacts with KLF15 to drive migration and invasion in osteosarcoma cell lines and promotes metastasis in allogeneic transplantation models. In addition, analyses of p53R248W chromatin immunoprecipitation peaks showed enrichment of KLF15 motifs in human osteoblasts. Taken together, these data identify unique mechanisms of action of the structural and contact mutants of p53. SIGNIFICANCE: The p53 DNA binding domain contact mutant p53R245W, but not the structural mutant p53R172H, interacts with KLF15 to drive metastasis in somatic osteosarcoma, providing a potential vulnerability in tumors expressing p53R245W mutation.

Molecular testing of DNA damage response pathways in prostate cancer patients.

PURPOSE OF REVIEW: Personalizing prostate cancer therapy requires germline and tumor molecular tests that predict who will respond to specific treatments and who may not. The review covers molecular testing of DNA damage response pathways, the first biomarker-driven precision target with clinical utility for treatment selection in patients with castration resistant prostate cancer (CRPC). RECENT FINDINGS: Recurrent somatic and germline variants cause deficiency of the mismatch repair (MMR) or homologous recombination (HR) pathways in about a quarter of CRPC patients. In prospective clinical trials, patients with deleterious variants in the MMR pathway more frequently experience a therapeutic response to immune checkpoint inhibitors (ICI). Similarly, somatic and germline events affecting HR predict response to poly(ADP) ribose polymerase inhibitor (PARPi) therapy. Molecular testing of these pathways currently involves assaying for loss of function variants in individual genes and for the genome-wide consequences of repair deficiency. SUMMARY: DNA damage response pathways are the first major area of molecular genetic testing in CRPC settings and offer insights into this new paradigm. Our hope is that eventually an arsenal of molecularly-guided therapies will be developed across many pathways to enable precision medicine options for most men with prostate cancer.

Integration of Consolidation Chemotherapy After Concurrent Chemoradiation in the Treatment of Locally Advanced Uterine Cervical Cancer.

Background: Despite the current standard of concurrent chemoradiation (CCRT), around 30-40% are still dying from locally advanced cervical cancer. Increasing the radiation dose further was not a feasible option, but addition of chemotherapy further was tried due to the different toxicity profiles of it. So, the use of consolidation chemotherapy beyond CCRT has been studied. Aim: To evaluate the efficacy, toxicity, tumour response and loco-regional control following consolidation chemotherapy after concurrent chemoradiation in locally advanced carcinoma cervix (LACC). Methods: The patients were randomized into two arms: the conventional arm (control arm, n = 30) patients received conventional treatment with weekly injection cisplatin (35 mg/m2) concurrently with pelvic external beam radiation (50 Gy/25 fraction, 2 Gy/fraction, 5 fraction weekly) followed by intracavitary radiotherapy of 21 Gy in 3 fractions of 7 Gy each by HDR brachytherapy. In the interventional arm (study arm, n = 30), patients received the standard treatment followed by 3 cycles of consolidation chemotherapy (paclitaxel + carboplatin) every three weekly. Results: Haematological toxicity (grade 3 anaemia and grade 1 leucopenia, grade 1 and 2 thrombocytopenia) was higher in the study group. Renal, hepatic and gastrointestinal toxicity was more in the study arm. Peripheral neuropathy was mostly seen in the study arm. Median follow-up was 9 months. Treatment response was better, and the rate of recurrence was less in the study arm. Conclusion: Addition of few cycles of consolidation chemotherapy after standard treatment is beneficial in patients with LACC with manageable toxicity and good compliance.

Google search activity in early psychosis: A qualitative analysis of internet search query content in first episode psychosis.

AIM: Manually explore the Google search queries of individuals with first episode psychosis prior to their first hospitalization, in effort to identify common themes and search interests during the period of emerging illness. METHODS: Individuals hospitalized for psychosis between December 2016 and September 2017 provided access to their Google archive data for manual qualitative evaluation of search content. Searches conducted during the 6-month time period prior to the participant's first hospitalization for psychosis were extracted and evaluated for search activity associated with mental health. RESULTS: Of 20 archives reviewed, 15 individuals (75%) searched for information classified by reviewers as related to mental health. Searches with content associated with delusions were found in 15 participant archives (75%). Searches related to negative symptoms including social withdrawal and decline in function were identified in 6 participant's search archives (30%). Four participants (20%) had searches that were associated with thought processes, and 2 participants (10%) searched for information on suicide. Four participants (20%) searched for information related to anxiety, whereas 3 participants (15%) had searches related to depressive symptoms. CONCLUSIONS: Individuals with early psychosis appear to be using the Internet for obtaining information about their early symptoms and experiences prior to their first contact with psychiatric care. Improving our understanding of the ways by which individuals with emerging psychosis search for information about their experiences online may help mental health clinicians tailor online resources in hopes of improving pathways to care and reducing the duration of untreated psychosis.

LncPRESS1 Is a p53-Regulated LncRNA that Safeguards Pluripotency by Disrupting SIRT6-Mediated De-acetylation of Histone H3K56.

Recent evidence suggests that lncRNAs play an integral regulatory role in numerous functions, including determination of cellular identity. We determined global expression (RNA-seq) and genome-wide profiles (ChIP-seq) of histone post-translational modifications and p53 binding in human embryonic stem cells (hESCs) undergoing differentiation to define a high-confidence set of 40 lncRNAs, which are p53 transcriptional targets. We focused on lncRNAs highly expressed in pluripotent hESCs and repressed by p53 during differentiation to identify lncPRESS1 as a p53-regulated transcript that maintains hESC pluripotency in concert with core pluripotency factors. RNA-seq of hESCs depleted of lncPRESS1 revealed that lncPRESS1 controls a gene network that promotes pluripotency. Further, we found that lncPRESS1 physically interacts with SIRT6 and prevents SIRT6 chromatin localization, which maintains high levels of histone H3K56 and H3K9 acetylation at promoters of pluripotency genes. In summary, we describe a p53-regulated, pluripotency-specific lncRNA that safeguards the hESC state by disrupting SIRT6 activity.

TRIM-ing Ligand Dependence in Castration-Resistant Prostate Cancer.

Prostate cancer is lethal when tumors evolve to activate androgen receptor signaling, which circumvents ligand-deprivation therapy. In this issue of Cancer Cell, Groner et al. show that histone reader and transcription co-regulator TRIM24 occupies a central role in this evolution, nominating inhibitors of TRIM24's bromodomain as a new therapeutic avenue.

Intratumoral morphologic and molecular heterogeneity of rhabdoid renal cell carcinoma: challenges for personalized therapy.

Rhabdoid histology in clear-cell renal cell carcinoma is associated with a poor prognosis. The prognosis of patients with clear-cell renal cell carcinoma may also be influenced by molecular alterations. The aim of this study was to evaluate the association between histologic features and salient molecular changes in rhabdoid clear-cell renal cell carcinoma. We macrodissected the rhabdoid and clear-cell epithelioid components from 12 cases of rhabdoid clear-cell renal cell carcinoma. We assessed cancer-related mutations from eight cases using a clinical next-generation exome-sequencing platform. The transcriptome of rhabdoid clear-cell renal cell carcinoma (n=8) and non-rhabdoid clear-cell renal cell carcinoma (n=37) was assessed by RNA-seq and gene expression microarray. VHL (63%) showed identical mutations in all regions from the same tumor. BAP1 (38%) and PBRM1 (13%) mutations were identified in the rhabdoid but not in the epithelioid component and were mutually exclusive in 3/3 cases and 1 case, respectively. SETD2 (63%) mutations were discordant between different histologic regions in 2/5 cases, with mutations called only in the epithelioid and rhabdoid components, respectively. The transcriptome of rhabdoid clear-cell renal cell carcinoma was distinct from advanced-stage and high-grade clear-cell renal cell carcinoma. The diverse histologic components of rhabdoid clear-cell renal cell carcinoma, however, showed a similar transcriptomic program, including a similar prognostic gene expression signature. Rhabdoid clear-cell renal cell carcinoma is transcriptomically distinct and shows a high rate of SETD2 and BAP1 mutations and a low rate of PBRM1 mutations. Driver mutations in clear-cell renal cell carcinoma are often discordant across different morphologic regions, whereas the gene expression program is relatively stable. Molecular profiling of clear-cell renal cell carcinoma may improve by assessing for gene expression and sampling tumor foci from different histologic regions.

Biphasic components of sarcomatoid clear cell renal cell carcinomas are molecularly similar to each other, but distinct from, non-sarcomatoid renal carcinomas.

Sarcomatoid transformation, wherein an epithelioid carcinomatous tumour component coexists with a sarcomatoid histology, is a predictor of poor prognosis in clear cell renal cell carcinoma. Our understanding of sarcomatoid change has been hindered by the lack of molecular examination. Thus, we sought to characterize molecularly the biphasic epithelioid and sarcomatoid components of sarcomatoid clear cell renal cell carcinoma and compare them to non-sarcomatoid clear cell renal cell carcinoma. We examined the transcriptome of the epithelioid and sarcomatoid components of advanced stage sarcomatoid clear cell renal cell carcinoma (n=43) and non-sarcomatoid clear cell renal cell carcinoma (n=37) from independent discovery and validation cohorts using the cDNA microarray and RNA-seq platforms. We analyzed DNA copy number profiles, generated using SNP arrays, from patients with sarcomatoid clear cell renal cell carcinoma (n=10) and advanced non-sarcomatoid clear cell renal cell carcinoma (n=155). The epithelioid and sarcomatoid components of sarcomatoid clear cell renal cell carcinoma had similar gene expression and DNA copy number signatures that were, however, distinct from those of high-grade, high-stage non-sarcomatoid clear cell renal cell carcinoma. Prognostic clear cell renal cell carcinoma gene expression profiles were shared by the biphasic components of sarcomatoid clear cell renal cell carcinoma and the sarcomatoid component showed a partial epithelial-to-mesenchymal transition signature. Our genome-scale microarray-based transcript data were validated in an independent set of sarcomatoid and non-sarcomatoid clear cell renal cell carcinomas using RNA-seq. Sarcomatoid clear cell renal cell carcinoma is molecularly distinct from non-sarcomatoid clear cell renal cell carcinoma, with its genetic programming largely shared by its biphasic morphological components. These data explain why a low percentage of sarcomatoid histology augurs a poor prognosis; suggest the need to modify the pathological grading system and introduce the potential for candidate biomarkers to detect sarcomatoid change preoperatively without specifically sampling the histological sarcomatoid component.

Inhibition of mTORC1/2 overcomes resistance to MAPK pathway inhibitors mediated by PGC1α and oxidative phosphorylation in melanoma.

Metabolic heterogeneity is a key factor in cancer pathogenesis. We found that a subset of BRAF- and NRAS-mutant human melanomas resistant to the MEK inhibitor selumetinib displayed increased oxidative phosphorylation (OxPhos) mediated by the transcriptional coactivator PGC1α. Notably, all selumetinib-resistant cells with elevated OxPhos could be resensitized by cotreatment with the mTORC1/2 inhibitor AZD8055, whereas this combination was ineffective in resistant cell lines with low OxPhos. In both BRAF- and NRAS-mutant melanoma cells, MEK inhibition increased MITF expression, which in turn elevated levels of PGC1α. In contrast, mTORC1/2 inhibition triggered cytoplasmic localization of MITF, decreasing PGC1α expression and inhibiting OxPhos. Analysis of tumor biopsies from patients with BRAF-mutant melanoma progressing on BRAF inhibitor ± MEK inhibitor revealed that PGC1α levels were elevated in approximately half of the resistant tumors. Overall, our findings highlight the significance of OxPhos in melanoma and suggest that combined targeting of the MAPK and mTORC pathways may offer an effective therapeutic strategy to treat melanomas with this metabolic phenotype.

Clinical significance of CTNNB1 mutation and Wnt pathway activation in endometrioid endometrial carcinoma.

BACKGROUND: Endometrioid endometrial carcinoma (EEC) is the most common form of endometrial carcinoma. The heterogeneous clinical course of EEC is an obstacle to individualized patient care. METHODS: We performed an integrated analysis on the multiple-dimensional data types including whole-exome and RNA sequencing, RPPA profiling, and clinical data from 271 EEC cases in The Cancer Genome Atlas (TCGA) to identify molecular fingerprints that may account for this clinical heterogeneity. Significance analysis of microarray was used to identify marker genes of each subtype that were subject to pathway analysis. Association of molecular subtypes with clinical features and mutation data was analyzed with the Mann Whitney, Chi-square, Fisher's exact, and Kruskal-Wallis tests. Survival analysis was evaluated with log-rank test. All statistical tests were two-sided. RESULTS: Four transcriptome subtypes with distinct clinicopathologic characteristics and mutation spectra were identified from the TCGA dataset and validated in an independent sample cohort of 184 EEC cases. Cluster II consisted of younger, obese patients with low-grade EEC but diminished survival. CTNNB1 exon 3 mutations were present in 87.0% (47/54) of Cluster II (P < .001) that exhibited a low overall mutation rate; this was statistically significantly associated with Wnt/ß-catenin signaling activation (P < .001). High expression levels of CTNNB1 (P = .001), MYC (P = .01), and CCND1 (P = .01) were associated with poorer overall survival in low-grade EEC tumors. CONCLUSIONS: CTNNB1 exon 3 mutations are likely a driver that characterize an aggressive subset of low-grade and low-stage EEC occurring in younger women.

The lncRNA PCAT29 inhibits oncogenic phenotypes in prostate cancer.

UNLABELLED: Long noncoding RNAs (lncRNA) have recently been associated with the development and progression of a variety of human cancers. However, to date, the interplay between known oncogenic or tumor-suppressive events and lncRNAs has not been well described. Here, the novel lncRNA, prostate cancer-associated transcript 29 (PCAT29), is characterized along with its relationship to the androgen receptor. PCAT29 is suppressed by DHT and upregulated upon castration therapy in a prostate cancer xenograft model. PCAT29 knockdown significantly increased proliferation and migration of prostate cancer cells, whereas PCAT29 overexpression conferred the opposite effect and suppressed growth and metastases of prostate tumors in chick chorioallantoic membrane assays. Finally, in prostate cancer patient specimens, low PCAT29 expression correlated with poor prognostic outcomes. Taken together, these data expose PCAT29 as an androgen-regulated tumor suppressor in prostate cancer. IMPLICATIONS: This study identifies PCAT29 as the first androgen receptor-repressed lncRNA that functions as a tumor suppressor and that its loss may identify a subset of patients at higher risk for disease recurrence. Visual Overview: http://mcr.aacrjournals.org/content/early/2014/07/31/1541-7786.MCR-14-0257/F1.large.jpg.

Translational genomics in cancer research: converting profiles into personalized cancer medicine.

Cancer genomics is a rapidly growing discipline in which the genetic molecular basis of malignancy is studied at the scale of whole genomes. While the discipline has been successful with respect to identifying specific oncogenes and tumor suppressors involved in oncogenesis, it is also challenging our approach to managing patients suffering from this deadly disease. Specifically cancer genomics is driving clinical oncology to take a more molecular approach to diagnosis, prognostication, and treatment selection. We review here recent work undertaken in cancer genomics with an emphasis on translation of genomic findings. Finally, we discuss scientific challenges and research opportunities emerging from findings derived through analysis of tumors with high-depth sequencing.

The long noncoding RNA SChLAP1 promotes aggressive prostate cancer and antagonizes the SWI/SNF complex.

Prostate cancers remain indolent in the majority of individuals but behave aggressively in a minority. The molecular basis for this clinical heterogeneity remains incompletely understood. Here we characterize a long noncoding RNA termed SChLAP1 (second chromosome locus associated with prostate-1; also called LINC00913) that is overexpressed in a subset of prostate cancers. SChLAP1 levels independently predict poor outcomes, including metastasis and prostate cancer-specific mortality. In vitro and in vivo gain-of-function and loss-of-function experiments indicate that SChLAP1 is critical for cancer cell invasiveness and metastasis. Mechanistically, SChLAP1 antagonizes the genome-wide localization and regulatory functions of the SWI/SNF chromatin-modifying complex. These results suggest that SChLAP1 contributes to the development of lethal cancer at least in part by antagonizing the tumor-suppressive functions of the SWI/SNF complex.

GAS6 receptor status is associated with dormancy and bone metastatic tumor formation.

Disseminated tumor cells (DTCs) are believed to lie dormant in the marrow before they can be activated to form metastases. How DTCs become dormant in the marrow and how dormant DTCs escape dormancy remains unclear. Recent work has shown that prostate cancer (PCa) cell lines express the growth-arrest specific 6 (GAS6) receptors Axl, Tyro3, and Mer, and become growth arrested in response to GAS6. We therefore hypothesized that GAS6 signaling regulates the proliferative activity of DTCs in the marrow. To explore this possibility, in vivo studies were performed where it was observed that when Tyro3 expression levels exceed Axl expression, the PCa cells exhibit rapid growth. When when Axl levels predominate, PCa cells remain largely quiescent. These findings suggest that a balance between the expression of Axl and Tyro3 is associated with a molecular switch between a dormant and a proliferative phenotype in PCa metastases.

Cancer genome sequencing: understanding malignancy as a disease of the genome, its conformation, and its evolution.

Advances in cancer genomics have been propelled by the steady evolution of molecular profiling technologies. Over the past decade, high-throughput sequencing technologies have matured to the point necessary to support disease-specific shotgun sequencing. This has compelled whole-genome sequencing studies across a broad panel of malignancies. The emergence of high-throughput sequencing technologies has inspired new chemical and computational techniques enabling interrogation of cancer-specific genomic and transcriptomic variants, previously unannotated genes, and chromatin structure. Finally, recent progress in single-cell sequencing holds great promise for studies interrogating the consequences of tumor evolution in cancers presenting with genomic heterogeneity.

Prevalence of prostate cancer metastases after intravenous inoculation provides clues into the molecular basis of dormancy in the bone marrow microenvironment.

Bone is the preferred metastasis site of advanced prostate cancer (PCa). Using an in vivo murine model of human PCa cell metastasis to bone, we noted that the majority of animals that develop skeletal metastasis have either spinal lesions or lesions in the bones of the hindlimb. Much less frequently, lesions develop in the bones of the forelimb. We therefore speculated whether the environment of the forelimb bones is not permissive for the growth of PCa. Consequently, data on tumor prevalence were normalized to account for the number of PCa cells arriving after intravascular injection, marrow cellularity, and number of hematopoietic stem cell niches. None of these factors were able to account for the observed differences in tumor prevalence. An analysis of differential gene and protein levels identified that growth arrest specific-6 (GAS6) levels were significantly greater in the forelimb versus hindlimb bone marrow. When murine RM1 cells were implanted into subcutaneous spaces in immune competent animals, tumor growth in the GAS6(-/-) animals was greater than in GAS6(+/+) wild-type animals. In an osseous environment, the human PC3 cell line grew significantly better in vertebral body transplants (vossicles) derived from GAS6(-/-) animals than in vossicles derived from GAS6(+/+) animals. Together, these data suggest that the differences in tumor prevalence after intravascular inoculation are a useful model to study the molecular basis of tumor dormancy. Importantly, these data suggest that therapeutic manipulation of GAS6 levels may prove useful as a therapy for metastatic disease.

384 hanging drop arrays give excellent Z-factors and allow versatile formation of co-culture spheroids.

We previously reported the development of a simple, user-friendly, and versatile 384 hanging drop array plate for 3D spheroid culture and the importance of utilizing 3D cellular models in anti-cancer drug sensitivity testing. The 384 hanging drop array plate allows for high-throughput capabilities and offers significant improvements over existing 3D spheroid culture methods. To allow for practical 3D cell-based high-throughput screening and enable broader use of the plate, we characterize the robustness of the 384 hanging drop array plate in terms of assay performance and demonstrate the versatility of the plate. We find that the 384 hanging drop array plate performance is robust in fluorescence- and colorimetric-based assays through Z-factor calculations. Finally, we demonstrate different plate capabilities and applications, including: spheroid transfer and retrieval for Janus spheroid formation, sequential addition of cells for concentric layer patterning of different cell types, and culture of a wide variety of cell types.