Kurt W. Fisher

Kinase Suppressor of Ras 1 (KSR1) Regulates PGC1α and Estrogen-Related Receptor α To Promote Oncogenic Ras-Dependent Anchorage-Independent Growth

ABSTRACT Kinase suppressor of ras 1 (KSR1) is a molecular scaffold of the Raf/MEK/extracellular signal-regulated kinase (ERK) cascade that enhances oncogenic Ras signaling. Here we show KSR1-dependent, but ERK-independent, regulation of metabolic capacity is mediated through the expression of peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) and estrogen-related receptor α (ERRα). This KSR1-regulated pathway is essential for the transformation of cells by oncogenic Ras. In mouse embryo fibroblasts (MEFs) expressing H-RasV12, ectopic PGC1α was sufficient to rescue ERRα expression, metabolic capacity, and anchorage-independent growth in the absence of KSR1. The ability of PGC1α to promote anchorage-independent growth required interaction with ERRα, and treatment with an inhibitor of ERRα impeded anchorage-independent growth. In contrast to PGC1α, the expression of constitutively active ERRα (CA-ERRα) was sufficient to enhance metabolic capacity but not anchorage-independent growth in the absence of KSR1. These data reveal KSR1-dependent control of PGC1α- and ERRα-dependent pathways that are necessary and sufficient for signaling by oncogenic H-RasV12 to regulate metabolism and anchorage-independent growth, providing novel targets for therapeutic intervention.

Drug-Induced Liver Injury

CONTEXT Drug-induced liver injury (DILI) represents a diverse set of responses following exposure to any manufactured or naturally occurring chemical compound. Drug-induced liver injury is of major concern owing to the ever increasing number of compounds introduced into the market for treatment of various diseases as well as the increasing popularity of herbals, which lend themselves to self-medication but are not rigorously regulated. OBJECTIVE To provide an overview of the prevalence, classification, and diagnosis of DILI with emphasis on pathogenesis and the role of a liver biopsy. To focus on the most common, emerging, and herbal agents that cause DILI with emphasis on the histologic pattern of injury observed. DATA SOURCES A review of the literature was drawn from the PubMed (US National Library of Medicine) repository, textbooks, and online databases. All figures were taken from cases seen at our tertiary referral center, which is 1 of 12 participating sites in the National Institutes of Health-funded Drug-Induced Liver Injury Network. CONCLUSIONS Drug-induced liver injury due to prescription, over-the-counter, and herbal products is a major cause of liver disease in the United States and around the world. Diagnosis of DILI is challenging because there is no single clinical, laboratory, or histologic feature specific to DILI. Accurate diagnosis requires establishing a causal relationship with the suspected agent and excluding competing causes of liver injury. The liver biopsy is an essential component in the management of DILI by offering clues to the underlying pathogenesis, providing prognostic information, and guiding therapy.

Molecular foundations for personalized therapy in prostate cancer

Prostate cancer is the most common and second most lethal cancer in men. The majority of prostate cancers are histologically similar to acinar adenocarcinomas and rely on androgen-dependent signaling for their development and progression. Androgen deprivation therapy is a mainstay of treatment regimens and we discuss the recent advancements in androgen-deprivation therapy. Recent advances in defining the genetic landscape of prostate cancer have shown that the depth of genetic heterogeneity surpasses what can be seen histologically and has the ability to redefine treatments. TMPRSS2-ETS family fusion proteins are unique to prostate cancer and we discuss their role in carcinogenesis, prognosis, and the development of TMPRSS2-ETS family gene fusion targeted therapy. Inactivation of the tumor suppressor PTEN leads to activation of the PI3K/Akt/mTOR pathway and we discuss the prognostic and treatment implications. Molecular genetic analysis has recently demonstrated that clinically aggressive high grade neuroendocrine prostate carcinomas contain a high prevalence of overexpression of Aurora A kinase and N-myc. We discuss the role of Aurora A kinase and N-myc in the development of the aggressive neuroendocrine phenotype and the development of targeted inhibitors of this specific genetic subtype. Lastly, we briefly discuss emerging genetic subtypes defined by either SPINK1 overexpression, CHD1 inactivation, or SPOP mutations. By reviewing the associations between the morphologic features and the molecular genetics of prostate cancer we hope to provide insight and guidance to the emerging options for targeted therapy.

AMPK Promotes Aberrant PGC1β Expression To Support Human Colon Tumor Cell Survival

ABSTRACT A major goal of cancer research is the identification of tumor-specific vulnerabilities that can be exploited for the development of therapies that are selectively toxic to the tumor. We show here that the transcriptional coactivators peroxisome proliferator-activated receptor gamma coactivator 1β (PGC1β) and estrogen-related receptor α (ERRα) are aberrantly expressed in human colon cell lines and tumors. With kinase suppressor of Ras 1 (KSR1) depletion as a reference standard, we used functional signature ontology (FUSION) analysis to identify the γ1 subunit of AMP-activated protein kinase (AMPK) as an essential contributor to PGC1β expression and colon tumor cell survival. Subsequent analysis revealed that a subunit composition of AMPK (α2β2γ1) is preferred for colorectal cancer cell survival, at least in part, by stabilizing the tumor-specific expression of PGC1β. In contrast, PGC1β and ERRα are not detectable in nontransformed human colon epithelial cells, and depletion of the AMPKγ1 subunit has no effect on their viability. These data indicate that Ras oncogenesis relies on the aberrant activation of a PGC1β-dependent transcriptional pathway via a specific AMPK isoform.

KSR1 and EPHB4 Regulate Myc and PGC1β To Promote Survival of Human Colon Tumors

ABSTRACT Identification and characterization of survival pathways active in tumor cells but absent in normal tissues provide opportunities to develop effective anticancer therapies with reduced toxicity to the patient. We show here that, like kinase suppressor of Ras 1 (KSR1), EPH (erythropoietin-producing hepatocellular carcinoma) receptor B4 (EPHB4) is aberrantly overexpressed in human colon tumor cell lines and selectively required for their survival. KSR1 and EPHB4 support tumor cell survival by promoting the expression of downstream targets, Myc and the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1β (PGC1β). While KSR1 promotes the aberrant expression of Myc and the PGC1β protein via a posttranscriptional mechanism, EPHB4 has a greater effect on Myc and PGC1β expression via its ability to elevate mRNA levels. Subsequent analysis of the posttranscriptional regulation demonstrated that KSR1 promotes the translation of Myc protein. These findings reveal novel KSR1- and EPHB4-dependent signaling pathways supporting the survival of colorectal cancer cells through regulation of Myc and PGC1β, suggesting that inhibition of KSR1 or EPHB4 effectors may lead to selective toxicity in colorectal tumors.

KSR as a therapeutic target for Ras-dependent cancers

ABSTRACT Introduction: Targeting downstream effectors required for oncogenic Ras signaling is a potential alternative or complement to the development of more direct approaches targeting Ras in the treatment of Ras-dependent cancers. Areas covered: Here we review literature pertaining to the molecular scaffold Kinase Suppressor of Ras (KSR) and its role in promoting signals critical to tumor maintenance. We summarize the phenotypes in knockout models, describe the role of KSR in cancer, and outline the structure and function of the KSR1 and KSR2 proteins. We then focus on the most recent literature that describes the crystal structure of the kinase domain of KSR2 in complex with MEK1, KSR-RAF dimerization particularly in response to RAF inhibition, and novel attempts to target KSR proteins directly. Expert opinion: KSR is a downstream effector of Ras-mediated tumorigenesis that is dispensable for normal growth and development, making it a desirable target for the development of novel therapeutics with a high therapeutic index. Recent advances have revealed that KSR can be functionally inhibited using a small molecule that stabilizes KSR in an inactive conformation. The efficacy and potential for this novel approach to be used clinically in the treatment of Ras-driven cancers is still being investigated.

TMPRSS2‐ERG gene fusion is rare compared to PTEN deletions in stage T1a prostate cancer

T1a prostate cancers (cancer found incidentally in transurethral resection, <5% of the tissue) are indolent tumors of the transition zone. The overexpression of ERG and the inactivation of PTEN have been shown to be important drivers of carcinogenesis in large series of prostate cancer, but the genetics of transition zone tumors have not been well characterized. We evaluated the status of ERG and PTEN in formalin‐fixed paraffin‐embedded tissue using immunohistochemical and FISH analysis in 54 T1a transition zone tumors. The protein expression of ERG was determined using a rabbit monoclonal antibody and nuclear staining was scored as positive or negative. The genomic status of ERG was determined using three colored FISH using an ERG‐TMPRSS2 tri‐color probe set. The protein expression of PTEN was determined using a rabbit monoclonal antibody and cytoplasmic, and nuclear staining was scored as positive or negative. The genomic status of PTEN was determined using dual color FISH with a PTEN probe and a CEP10 probe. We found ERG rearrangement in 2 of 54 tumors (4%), one with protein overexpression by immunohistochemistry. PTEN inactivation was seen in 13 of 54 tumors (24%). Nine of the 13 PTEN alleles were inactivated by hemizygous deletion. No homozygous PTEN deletion was observed. PTEN deletion and ERG rearrangement were mutually exclusive. ERG rearrangement was rare compared to peripheral zone tumors and to PTEN inactivation in T1a transition zone tumors.

A Functional Signature Ontology (FUSION) screen detects an AMPK inhibitor with selective toxicity toward human colon tumor cells

AMPK is a serine threonine kinase composed of a heterotrimer of a catalytic, kinase-containing α and regulatory β and γ subunits. Here we show that individual AMPK subunit expression and requirement for survival varies across colon cancer cell lines. While AMPKα1 expression is relatively consistent across colon cancer cell lines, AMPKα1 depletion does not induce cell death. Conversely, AMPKα2 is expressed at variable levels in colon cancer cells. In high expressing SW480 and moderate expressing HCT116 colon cancer cells, siRNA-mediated depletion induces cell death. These data suggest that AMPK kinase inhibition may be a useful component of future therapeutic strategies. We used Functional Signature Ontology (FUSION) to screen a natural product library to identify compounds that were inhibitors of AMPK to test its potential for detecting small molecules with preferential toxicity toward human colon tumor cells. FUSION identified 5′-hydroxy-staurosporine, which competitively inhibits AMPK. Human colon cancer cell lines are notably more sensitive to 5′-hydroxy-staurosporine than are non-transformed human colon epithelial cells. This study serves as proof-of-concept for unbiased FUSION-based detection of small molecule inhibitors of therapeutic targets and highlights its potential to identify novel compounds for cancer therapy development.

Prognostic value of programmed death ligand 1, p53, and Ki-67 in patients with advanced-stage colorectal cancer

Current prognostic indicators are ineffective for identifying advanced-stage colorectal cancer (CRC) patients with high risk of recurrence after surgical resection. We investigated the prognostic value of p53, Ki-67, and programmed death ligand 1 (PD-L1) in 254 patients with stage II and III CRC. The expression of p53 was positive in 63% of cases. Up-regulation of p53 was associated with smaller tumor size (P=.001) and higher Ki-67 labeling index (LI) (P=.031). The tumor Ki-67 LI was high (≥20%) in 197 (78%) of the patients. High Ki-67 LI was associated with higher TNM stage (P=.031), positive p53 expression (P=.031), and negative PD-L1 expression (P=.003). The 5-year relapse-free survivals (RFS) were 53% and 89%, respectively, for the p53-positive and Ki-67 LI-high patients and the p53-negative and Ki-67 LI-low patients (P<.001). In univariate analysis, negative p53 (P=.001), low Ki-67 LI (P=.006), low PD-L1 expression (P=.044), low TNM stage (P<.001), rectosigmoid location (P=.026), and small size (P=.013) were significantly related to RFS. In multivariate Cox regression analysis, positive p53 expression (hazard ratio [HR]: 2.48; 95% confidence interval: 1.34-4.59, P=.004), high Ki-67 LI (HR, 2.62; 95% CI, 1.12-6.14, P=.027) and high TNM stage (HR, 2.598; 95% CI, 1.55-4.37, P<.001,) were independent predictors of unfavorable prognosis. In summary, PD-L1, Ki-67, and p53 staining individually had significant prognostic value for patients with stage II and III CRC. Moreover, combining p53 H-score ≥35 and Ki-67 LI ≥20% identifies patients with poor clinical outcome.

Identification of novel biomarker and therapeutic target candidates for diagnosis and treatment of follicular carcinoma

Distinguishing follicular carcinoma from follicular adenoma, based on cytomorphological features, has always been challenging to cytopathologists. Identification of biomarkers for improving diagnostic accuracy is important for clinical management. Meanwhile, it is critical to identify therapeutic target candidates for treatment of follicular carcinoma. Currently, no reliable diagnostic protein biomarkers and therapeutic targets are available. To explore novel protein biomarker and therapeutic target candidates, a liquid chromatography-tandem mass spectrometry approach was applied to analyze control, follicular adenoma, and follicular carcinoma using formalin-fixed, paraffin-embedded tissue samples. The proteomics analysis revealed 80 protein biomarker candidates for diagnosis of thyroid follicular carcinoma. The candidates were prioritized into three categories and ranked within each category. Using the proteomics data and bioinformatics results, the top seven biomarker candidates were coiled-coil-helix-coiled-coil-helix domain-containing protein 2, mitochondrial (CHCHD2), succinyl-CoA ligase [GDP-forming] subunit beta, mitochondrial (SUCLG2), stomatin-like protein 2, mitochondrial (STOML2), ES1 protein homolog, mitochondrial (C21orf33), fumarate hydratase, mitochondrial (FH), 3-hydroxyacyl-CoA dehydrogenase type-2 (HSD17B10), and electron transfer flavoprotein subunit beta (ETFB); and the top seven therapeutic target candidates were insulin receptor (INSR), Myc proto-oncogene protein (MYC), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A), gastrin (GAST), N-myc proto-oncogene protein (MYCN), transforming growth factor beta-1 (TGFB1), and interleukin-4 (IL4). Immunohistochemical staining of SUCLG2 and ETFB is highly consistent with the discovery of proteomics, revealing that SUCLG2 has a sensitivity of 75% and a specificity of 80% to distinguish follicular carcinoma from follicular adenoma based on a specific cut-off score calculated from the IHC staining percentage and intensity. BIOLOGICAL SIGNIFICANCE Distinguishing follicular carcinoma from follicular adenoma, based on cytomorphological features, has always been challenging to cytopathologists. Fourteen biomarker candidates were identified. Two of them were validated with Immunohistochemical staining. The Identification of biomarkers for improving diagnostic accuracy is important for clinical management.