Abstract C044: Inter-ethnic differential gene expression in stage II recurrent colorectal cancers

Inter-ethnic differential gene expression in stage II recurrent colorectal cancers Prachi Bajpai1, Amr Elholy1, Michael Behring1, Dongquan Chen2, 3, Kevin Hale1, Sumit Agrawal1, Hyung-Gyoon Kim1, Trafina Jadhav1, Temegsen Samuel4, Upender Manne1, 3 1Department of Pathology, 2Division of Preventive Medicine, Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, Alabama, USA, 3O’Neal Comprehensive Cancer Center of UAB, Birmingham; 4Department of Pathobiology, College of Veterinary Medicine, Tuskegee University, Tuskegee, Alabama, USA Background and Objective: For colorectal cancer (CRC), the second most common cause of cancer-related death in the US, there are racial/ethnic disparities in incidence and mortality. Of these patients, 25-35% with pathologic Stage II CRCs exhibit recurrence after surgery with curative intent. Relative to Caucasian (CA) patients, African American (AA) patients with CRC have a 20% higher stage-specific mortality. The present study delineates a distinct gene expression profile, specific for Stage II CRCs, based on disease recurrence and patient race/ethnicity. Methods: We obtained gene expression profiles for Stage II CRCs from 16 AA and 30 CA patients by the use of Affymetrix GeneChip microarrays. Samples from patients with recurrent disease, within 5 years post-surgery, were compared to those with non-recurrent CRCs within 5 years post-surgery. For comparison between AA with CA patients, gene expression was assessed. Results: For recurrent CRCs, there were nine genes common to AA and CA patients, suggesting a common gene signature specific for Stage II disease. For tumors, relative to their corresponding normal tissues, there was higher expression of five of these genes; the direction of association with disease recurrence was distinct with race/ethnicity. GFM2, DCAF17, and GEN1 had a positive association with recurrence in CAs and a negative association with recurrence in AAs. Additionally, for recurrent patients, TAPBP and FEZ were upregulated in AAs and downregulated in CAs (False Discovery Rate <0.05 for all genes). BCL2L2, OXA1L, AHNAK2, and MEGF6 were consistently overexpressed in CRCs of both race/ethnicity groups. Currently, we are validating these findings in a prospective Stage II CRC cohort to correlate observations with time to recurrence. Conclusion: The present study identifies molecular signatures, specific for Stage II CRCs, for patients of two ethnic backgrounds, and contribute to a better understanding of the CRC health disparities for AAs and CA. This work was supported by a NIH/NCI grant (U54CA118948).

Citation Format: Prachi Bajpai, Amr Elholy, Michael Behring, Dongquan Chen, Kevin Hale, Sumit Agrawal, Hyung-Gyoon Kim, Trafina Jadhav, Temegsen Samuel, Upender Manne. Inter-ethnic differential gene expression in stage II recurrent colorectal cancers [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr C044.

Prospective Study of Cardiac Events During Proteasome Inhibitor Therapy for Relapsed Multiple Myeloma

PURPOSE

Cardiovascular adverse events (CVAEs) can occur during proteasome inhibitor (PI) therapy. We conducted a prospective, observational, multi-institutional study to define risk factors and outcomes in patients with multiple myeloma (MM) receiving PIs.

PATIENTS AND METHODS

Patients with relapsed MM initiating carfilzomib- or bortezomib-based therapy underwent baseline assessments and repeated assessments at regular intervals over 6 months, including cardiac biomarkers (troponin I or T, brain natriuretic peptide [BNP], and N-terminal proBNP), ECG, and echocardiography. Monitoring occurred over 18 months for development of CVAEs.

RESULTS

Of 95 patients enrolled, 65 received carfilzomib and 30 received bortezomib, with median 25 months of follow-up. Sixty-four CVAEs occurred, with 55% grade 3 or greater in severity. CVAEs occurred in 51% of patients treated with carfilzomib and 17% of those treated with bortezomib (P = .002). Median time to first CVAE from treatment start was 31 days, and 86% occurred within the first 3 months. Patients receiving carfilzomib-based therapy with a baseline elevated BNP level higher than 100 pg/mL or N-terminal proBNP level higher than 125 pg/mL had increased risk for CVAE (odds ratio, 10.8; P < .001). Elevated natriuretic peptides occurring mid-first cycle of treatment with carfilzomib were associated with a substantially higher risk of CVAEs (odds ratio, 36.0; P < .001). Patients who experienced a CVAE had inferior progression-free survival (log-rank P = .01) and overall survival (log-rank P < .001). PI therapy was safely resumed in 89% of patients, although 41% required chemotherapy modifications.

CONCLUSION

CVAEs are common during PI therapy for relapsed MM, especially with carfilzomib, particularly within the first 3 months of therapy. CVAEs were associated with worse overall outcomes, but usually, discontinuation of therapy was not required. Natriuretic peptides were highly predictive of CVAEs; however, validation of this finding is necessary before uniform incorporation into the routine management of patients receiving carfilzomib.

The combined survival effect of codon 72 polymorphisms and p53 somatic mutations in breast cancer depends on race and molecular subtype

Background

The codon 72 polymorphism in the p53 gene relates to the risk of breast cancer (BC), but this relationship in racially diverse populations is not known. The present study examined the prognostic value of this polymorphism for African American (AA) and Caucasian (CA) BC patients separately and considered the confounding variables of molecular subtypes and somatic mutations in p53.

Methods

Tissue sections of BCs from 116 AAs and 160 CAs were evaluated for p53 mutations and genotyped for the codon 72 polymorphism. The relationships of phenotypes to clinicopathologic features were determined by χ2 analyses; patient survival was estimated by Kaplan-Meier univariate and Cox regression multivariate models in a retrospective cohort study design.

Results

The proportion of single nucleotide polymorphism (SNP) 72 alleles differed for races. Many cancers of AAs were Pro/Pro, but most for CAs were Arg/Arg. A higher frequency of missense p53 mutations was evident for AAs. There was an interaction between the SNP allele and p53 mutations for AA women only. The proportion of women with both the Pro/Pro allele and a p53 somatic mutation was higher for AA than CA women. The interaction between missense p53 mutations and Pro/Pro had a negative effect on survival, particularly for AAs with luminal cancers.

Conclusions

For BCs, the survival effect of SNP72 combined with a p53 missense mutation is dependent on race and molecular subtype. Although such a mutation is a marker of poor prognosis, it is relevant to identify the variant Pro/Pro in the case of AAs, especially those with luminal subtypes of BC.

Effect of surfactants and hydrophilic polymers on the stability of an antihypertensive drug candesartan cilexetil: Evaluation by HPLC

OBJECTIVES

The objective of this study is to investigate the effect of surfactants (polysorbate 80 and sodium lauryl sulphate) and hydrophilic polymers (polyvinylpyrrolidone and polyethylene glycol 6000) on the stability of candesartan cilexetil under isothermal stress conditions (100°C, 48h).

METHODS

HPLC method was employed to evaluate the drug content and formation of degradation products in stress samples. Drug and degradation products were separated on Hypersil BDS C18 (250×4.6mm, 5μ) column using acetonitrile-water (pH 2.8) in the ratio of 85:15% v/v as a mobile phase.

RESULT

Similar degradation behaviour of drug was observed with polyvinylpyrrolidone, polyethylene glycol 6000 and polysorbate 80; four common degradation peaks were observed at the retention time of 3.7, 4.5, 7.8 and 11minutes. One extra common degradation peak of very low intensity was also observed with polyethylene glycol 6000 and polysorbate 80 at the retention time of 4.2min. The drug was eluting at the retention time of 5.4min. In the case of sodium lauryl sulphate, two prominent degradation peaks were observed at the retention time of 3.7 and 13.25min along with few very low-intensity degradation peaks.

CONCLUSION

The drug showed 41%, 64%, 72% and 98% degradation in presence of polyvinylpyrrolidone, polyethylene glycol 6000, polysorbate 80 and sodium lauryl sulphate, respectively.

Molecular Biomarkers of Colorectal Cancer and Cancer Disparities: Current Status and Perspective

This review provides updates on the efforts for the development of prognostic and predictive markers in colorectal cancer based on the race/ethnicity of patients. Since the clinical consequences of genetic and molecular alterations differ with patient race and ethnicity, the usefulness of these molecular alterations as biomarkers needs to be evaluated in different racial/ethnic groups. To accomplish personalized patient care, a combined analysis of multiple molecular alterations in DNA, RNA, microRNAs (miRNAs), metabolites, and proteins in a single test is required to assess disease status in a precise way. Therefore, a special emphasis is placed on issues related to utility of recently identified genetic and molecular alterations in genes, miRNAs, and various "-omes" (e.g., proteomes, kinomes, metabolomes, exomes, methylomes) as candidate molecular markers to determine cancer progression (disease recurrence/relapse and metastasis) and to assess the efficacy of therapy in colorectal cancer in relation to patient race and ethnicity. This review will be useful for oncologists, pathologists, and basic and translational researchers.

Abstract 2776: Codon 72 and Intron-3 polymorphisms in TP53 are risk factors for breast cancer

Purpose: A single nucleotide polymorphism (SNP) in exon-4 of the TP53 gene (Arg72Pro) has been associated with an increased risk of developing various human malignancies. Since a 16-base pair polymorphism (insertion/duplication) intron-3 (PIN3) is in linkage disequilibrium with Arg72Pro of TP53, we assessed whether these two polymorphisms serve as breast cancer risk alleles for African Americans (AAs) and non-Hispanic Caucasians (CAs).

Methods: Genomic DNA was extracted from formalin-fixed, paraffin-embedded invasive ductal carcinoma tissues [cases, n = 120 (AAs = 55 and CAs = 65)] and from blood of healthy women [controls, n = 152 (AA = 74 and CAs = 78)]. Exon-4 of TP53 was amplified by PCR using exon-specific primers, followed by Sanger sequencing. Identification of SNP was done by using DNASTAR software. TP53 PIN3 polymorphism was detected by amplifying genomic DNA using specific primers followed by gel electrophoresis. The A1 allele (no duplication) resulted in 162 bp fragment and the A2 allele (with 16 bp duplication) resulted in 178 bp fragment. The phenotypes of Arg72Pro (Arg/Arg, Arg/Pro, and Pro/Pro) were correlated with PIN3 status, clinicopathologic features, race/ethnicity, and patient survival using the χ2 test and Kaplan-Meier analyses. A p value of &lt;0.05 was considered statistically significant.

Results: In cases, the Arg/Arg/, Pro/Arg, and Pro/Pro phenotypes were 15%, 31%, and 55% in AAs and 57%, 29%, and 14% in CAs (p&lt;0.001), respectively. A similar distribution was observed in controls (16%, 42%, and 42% in AAs and 56%, 37%, and 6% in CAs) (p&lt;0.001). When compared to ER positive, a higher frequency of Arg/Pro or Pro/Pro was noted in estrogen-negative breast cancers (p = 0.03) in both racial groups. However, no significant survival difference in these racial groups was observed when Pro carriers were compared with Arg/Arg cases (log rank, p = 0.565). Frequencies of PIN3 polymorphisms (A1A1, A1A2, and A2A2) were similar in both cases and controls; however, overall A1A1 frequency was higher than the other two genotypes of PIN3. The phenotype Pro/Pro, was strongly associated with A1A1 polymorphism in both racial groups of breast cancer patients (p&lt;0.000078).

Conclusion: These preliminary findings suggest that Arg72Pro polymorphism and PIN3 in TP53 are related with higher breast cancer susceptibility for both African American and non-Hispanic Caucasian patients. This work was supported by a pilot grant from UAB Breast SPORE grant of the National Institutes of Health/National Cancer Institute (5P50CA089019).

Citation Format: Trafina Jadhav, Jesus Salazar-Gonzalez, Shantel Hebert-Magee, Michael Behring, Balananda-Dhurjati Putcha, Jeehyun Helen Bae, Andra Frost, Isam-Eldin Eltoum, Sejong Bae, Upender Manne. Codon 72 and Intron-3 polymorphisms in TP53 are risk factors for breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2776. doi:10.1158/1538-7445.AM2015-2776

Abstract 4004: Prognostic value of miRNAs in breast cancer varies with patient race and molecular subtype

Background: MicroRNAs (miRNAs) may serve as biomarkers for breast cancer (BC) diagnosis and prognosis. Since their clinical value based on race/ethnicity and molecular subtypes has not been studied, we evaluated the prognostic significance of a panel of miRNAs in luminal and triple-negative BCs (TNBCs) of African Americans (AAs) and non-Hispanic Caucasians (CAs).

Methods: TaqMan® assays were used to quantify levels of miR-21, miR-106a, miR-206, miR-155, miR-210, and miR-335 in 151 BCs and corresponding normal tissues of 80 AAs (luminal = 24 and TNBCs = 56) and 71 CAs (luminal = 27 and TNBC = 44). Fold changes in levels between tumor-normal pairs were used to categorize the tumors into high- and low-expression groups. The levels of miRNAs were correlated with molecular subtype, patient race/ethnicity, and overall survival by Kaplan-Meier univariate and Cox regression multivariate analyses. Further, the added predictive value of these miRNAs to a baseline prediction model consisting of standard clinical risk factors was evaluated at 2-, 5-, and 8-years post-surgery based on positive predictive curves.

Results: In BC tissues, miR-21, miR-106a, miR-155, miR-206, and miR-210 were up-regulated, and miR-335 was down-regulated. For the combined population, univariate and multivariate analyses showed that high levels of miR-21 (adjusted HR = 2.91, 95% CI: 1.27-6.62) and miR-106a (adjusted HR = 2.49, 95% CI: 1.04-5.97) and down-regulation of miR-335 (adjusted HR = 2.97, 95% CI: 1.35-5.54) were associated with poor survival. In multivariate analyses by race, high miR-21 (HR = 7.35, 95% CI: 2.46-21.98) and low miR-335 (HR = 14.13, 95% CI: 2.93-68.13) were indicators of poor survival in only CA patients. Additionally, expression levels of miR-21 aided in identifying risk of death in CA patients with either molecular subtype. In CAs, differences in the area under the positive predictive curve (ΔAUC) between the models with and without miR-21 were 0.077 (95% CI = 0.007-0.154) and 0.053 (95% CI = 0.002-0.128) at 5 and 8 years after surgery, respectively. In TNBCs of both racial groups, addition of miR-106a increased predictive accuracy at 5 (ΔAUC = 0.026, 95% CI = 0.001-0.068) and 8 years (ΔAUC = 0.022, 95% CI = 0-0.061) post-surgery. No miRNA was helpful in identifying patients at high risk of death due to luminal BCs or to AA ethnicity.

Conclusions: High levels of miR-106a and miR-21 and low levels of miR-335 are independent prognostic markers of BCs. Furthermore, miR-21 has added predictive value above the standard clinical risk factors for CAs and miR-106a has added predictive value for TNBCs. In evaluation of the clinical utility of miRNAs, patient race and molecular types of BCs should be considered. This work was supported by a pilot grant from UAB Breast SPORE grant of the National Institutes of Health/National Cancer Institute (5P50CA089019).

Citation Format: Balananda-Dhurjati Kumar Putcha, Trafina Jadhav, Michael P. Behring, Sejong Bae, Andra R. Frost, Isam-Eldin Eltoum, Li Chen, Heidi L. Weiss, William E. Grizzle, Upender Manne. Prognostic value of miRNAs in breast cancer varies with patient race and molecular subtype. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4004. doi:10.1158/1538-7445.AM2015-4004

Recurrence score distributions in stage II colon cancers of African American (AA) and Caucasian (CA) patients

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Background: The 12-gene colon cancer assay (Oncotype DX) can identify groups of stage II colon cancer patients with lower or higher recurrence risk, but distribution of scores based on race/ethnicity has not been assessed. This study compared the distribution of Recurrence Score results and gene expression profiles between African American (AA) and Caucasian (CA) stage II colon cancer patients. Methods: Stage II colon cancer patients were identified from tumor registry data from four institutions: University of Arkansas for Medical Sciences, Little Rock; Veterans Administration Medical Center, Little Rock; Baptist Medical Center, Memphis, and University of Alabama at Birmingham. The 12-gene assay and mismatch repair (MMR) status were performed on formalin-fixed paraffin-embedded tissues by Genomic Health (Redwood City, CA). T-test and Wilcoxon test were used to compare data from the two groups (SAS Enterprise Guide 5.1). Results: Of the 244 subjects, there were 118 women (63 AA, 55 CA) and 126 men (59 AA, 67 CA). Median ages (years) were 66 for AAs and 68 for CAs. Age, gender, surgery year, pathologic T-Stage, tumor location, number of nodes examined, lympho-vascular invasion, and MMR status were not significantly different between groups (p>0.05). Recurrence Score results between AAs (mean 27.9; SD 12.8) and CAs (mean 28.1; SD 11.8) were not statistically different (p>0.05). The proportion of patients with high Recurrence Score values (≥41) was similar between the groups (17/122 AA; 15/122 CA). None of the gene expression variables, either single genes or gene groups, (cell cycle group, stromal group, BGN1, FAP, INHBA1, Ki67, MYBL2, cMYC3 and GADD45B) was significantly different between the racial groups (p>0.05). After controlling for clinical and pathologic covariates, means and distributions of Recurrence Score and gene expression profiles still showed no statistical significance between racial groups (p>0.05). Conclusions: In a cohort of AA and CA stage II colon cancer patients with similar clinical characteristics, the distribution of Recurrence Score results and gene expression data were similar between AA and CA patients.

Abstract C22: Overexpression of miR-181b and underlying molecular mechanisms in aggressive progression of African American colorectal cancers

Background: MicroRNAs (miRs) are 19 to 24 nucleotide sequences that regulate cell proliferation, differentiation, and apoptosis. mir-181b is involved in tumor initiation and progression of several human malignancies, including colorectal cancers (CRCs). Our recent study of CRCs has demonstrated that increased expression of miR-181b is an indicator of poor patient prognosis, especially for African American patients with Stage III CRCs [Clin Cancer Res; 19(14); 1–11. 2013]. In the current study, we investigated molecular mechanisms of miR-181b over-expression in aggressive progression of CRCs.

Methods: The effects of miR-181b over-expression on cell migration, apoptosis, and the cell cycle were analyzed. Putative molecular targets of miR-181b were identified by in silico analysis. miR-181b mediated, post-transcriptional regulation of these targets was assessed in CRC cell lines (HCT116wt/wt, HCT116 p53-/- and SW480 p53mut/mut) subjected to transient transfection. The targets were validated by measuring their mRNA expression levels, by qRT-PCR, in Stage III CRC tissues (n=18), which exhibited elevated levels of miR-181b. Further, luciferase assays were performed to assess a direct interaction between miR-181b and the 3′UTR of its target genes.

Results: Transfection studies indicated that, in CRC cells, over-expression of miR-181b enhanced the rate of migration, diminished apoptosis, and shifted CRC cells from the G1 to the G2/M phase in a p53-dependent manner. Fourteen putative molecular targets of miR-181b were identified by in silico analysis, and miR-181b mediated post-transcriptional regulation of these targets was validated in CRC cell lines by qRT-PCR. Upon over-expression of miR-181b, integrin alpha-3 (cell surface adhesion molecule that mediates cell-adhesion to extra cellular matrix) was up-regulated, and BCL2L11 (apoptosis facilitator) and TNF-alpha (cytokine that has been implicated in tumor regression and also causes apoptosis) were down-regulated. Also, these targets were validated in human CRC tissues that exhibited elevated miR-181b levels (n=8). Finally, the direct interaction of miR-181b with the target gene 3′UTRs was confirmed by luciferase assays.

Conclusions: These results demonstrate that, in CRCs, miR-181b post-transcriptionally regulates expression of integrin alpha-3, BCL2L11, and TNF-alpha and also regulates the cell cycle, migration, and apoptosis. This study was funded in part by the National Cancer Institute of the National Institute of Health UAB/TU/MSM Partnership grant (U54 CA118948).

Citation Format: Balananda-Dhurjati Kumar Putcha, Brittany Michelle Holt, Liselle Bovell, Trafina Jadhav, Upender Manne. Overexpression of miR-181b and underlying molecular mechanisms in aggressive progression of African American colorectal cancers. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C22. doi:10.1158/1538-7755.DISP13-C22

Abstract PR5: Prognostic value of miRNAs in breast cancer: Molecular type and patient race

Background: MicroRNAs (miRNAs) are a class of conserved, non-coding RNAs that are dysregulated in various cancers, including breast cancers. The potential of miRNAs to serve as biomarkers for breast cancer diagnosis and prognosis is being explored, but their clinical value based on race/ethnicity and molecular subtypes (luminal and triple negative breast cancers, TNBCs) has not been examined. Thus, we evaluated expression levels of a panel of miRNAs in luminal (A and B) breast cancers and TNBCs of African Americans (Blacks) and non-Hispanic Caucasians (Whites). We further evaluated the prognostic value of miRNAs based on molecular type of breast cancer and patient race.

Methods: TaqMan® miRNA assays were used to quantify expression of miR-181a, miR181b, miR-21, miR-106a, miR-155, miR-210, miR-335, miR-206, and miR-126 in 105 breast cancers (luminal=51 and TNBCs=54) and their corresponding benign/normal tissues. Cancer tissuefrom 48 Blacks (luminal=23 and TNBCs=25) and 57 Whites (luminal=28 and TNBC=29) were analyzed. Fold change in the expression levels between tumor-normal pairs were determined using the 2-∆∆Ct method. A cutoff value for each miRNA was determined by utilizing the Cutoff Finder software application [PLoS ONE 7(12):e51862, 2012]. The cutoff values were used to categorize the tumors into two groups (High expression or positive and low expression or negative). The expression status of tumors was correlated with patient overall survival by univariate Kaplan-Meier analysis.

Results: Since the survival probabilities of Blacks and Whites with TNBCs (log rank, p=0.899) were similar, TNBCs from both racial groups were pooled. Similarly, no survival differences were noted in patients of both racial groups with luminal breast cancers (log rank, p=0.178). Therefore, luminal cancers of Blacks and Whites were also pooled together to perform survival analyses based on miRNA expression levels. MiRNA expression profiling studies indicated that, in both the racial groups, miR-181a, miR-181b, miR-21, miR-106a, miR-155, and miR-210 were up-regulated in luminal cancers and TNBCs. In contrast, miR-335, miR-206, and miR-126 were down-regulated in both molecular types. When the prognostic value of miRNAs was evaluated in each molecular type separately, it was found that over-expression of miR-106a (p=0.037) and miR-210 (p=0.039) were associated with poor prognosis of TNBCs. However, none of the evaluated miRNAs were useful in assessing the prognosis of patients with luminal cancers.

Conclusions: These findings suggest that increased expression of miR-106a and miR-210 were poor prognostic indicators of TNBCs collected from both Black and White patients. Additionally, our results suggest that in the evaluation of clinical utility of miRNAs molecular types of breast cancer should be considered. This study was funded in part by the National Cancer Institute of the National Institute of Health UAB/TU/MSM Partnership grant (U54 CA118948).

This abstract is also presented as Poster C21.

Citation Format: Balananda-Dhurjati Kumar Putcha, Trafina Jadhav, Shantel Hebert-Magee, Jeehyun Helen Bae, Andra R. Frost, Isam-Eldin Eltoum, Sejong Bae, Upender Manne. Prognostic value of miRNAs in breast cancer: Molecular type and patient race. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr PR5. doi:10.1158/1538-7755.DISP13-PR5

Abstract 3820: Expression of ST6Gal-1 in colorectal cancer and patient prognosis

Background: ST6Gal-1 sialyltransferase, a type II membrane protein that catalyzes the transfer of sialic acid to the N-glycans of certain receptors, is upregulated in several cancers, including colorectal cancers (CRCs), and its levels correlate with metastatic potential. Therefore, we investigated its prognostic value in CRCs.

Methodology: Formalin-fixed, paraffin-embedded CRC tissues from African Americans (Blacks) (n=50) and non-Hispanic Caucasians (Whites) (n=51) patients were evaluated for immunohistochemical (IHC) expression of ST6Gal-1. IHC expression was assessed using an anti-human ST6Gal-1 polyclonal antibody (R&D Systems) with antigen retrieval. The antibody-antigen complex was detected by the Immpact NovaRed system (Vector Labs). A semiquantitative immunostaining scoring system (ISS) on a scale of 0-4 was developed to assess the ST6Gal-1 expression, and a cutoff value (1.2 ISS) was determined by the bootstrap method. This value was used to classify tumors as low- or high-ST6Gal-I expressors. Previously, these tissues were evaluated for p53 nuclear accumulation (p53nac), an indicator of abnormal p53, by IHC. ST6Gal-1 expression levels were correlated with demographic and clinicopathologic features and with patient survival.

Results: Increased ST6Gal-1 expression was observed in all CRCs as compared to their corresponding normal tissues. The overall frequency of CRCs with increased ST6Gal-1 expression was 80%; it was more commonly found in Blacks (88%, 44 of 50) than in Whites (70%, 36 of 51) (X2 p=0.031). Also, increased expression was associated with p53nac, and ST6Gal-1 expression was higher in CRCs that exhibited p53nac (87%, 42 of 48) relative to CRCs without p53nac (70%, 35 of 50) (X2 p = 0.034). Moreover, patients with CRCs with high ST6Gal-1 had lower median survival (29.3 months) relative to those with low ST6Gal-1 expression (58.5 months).

Conclusions: These preliminary findings suggest that increased expression of ST6Gal-1 expression, found predominantly in Blacks patients and in CRCs with abnormal p53, is associated with poor patient survival.

Citation Format: Trafina Jadhav, Saksham Narang, Jeehyun Bae, Matthew Schultz, Isam-Eldin Eltoum, Susan Bellis, Sejong Bae, Upender Manne. Expression of ST6Gal-1 in colorectal cancer and patient prognosis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3820. doi:10.1158/1538-7445.AM2014-3820

Abstract 4031: Distinct gene expression profile of recurrent stage II colorectal cancers in African American and Caucasian American patients

Objective: To determine gene expression profile of Stage II colorectal cancers (CRCs) based on disease recurrence and patient race/ethnicity.

Background: About 25-35% of Stage II CRCs recur after potentially curative surgery. Furthermore, the incidence, recurrence, and mortality rates for CRC are higher in African Americans (AAs) relative to Caucasian Americans (CAs), even when they are diagnosed with early stage disease. Differences in tumor biology may contribute to this race-based disparity. Thus, identification of these ‘high-risk’ patients is an unmet medical need.

Methods: Using GeneChip microarray technology, we obtained gene expression profiles for Stage II CRCs from 16 AA and 30 CA patients. Samples from recurrent disease, within 5 years post-surgery (n=5 in AA, n= 9 in CA) were compared against non-recurrent, within 10 years post-surgery, (n=11 in AA, and n=21 in CA) samples. The data were analyzed for expression differences at the gene level comparing AA with CA patients and further analyzed for functions and pathways.

Results: In the samples of recurrent CRCs, a significant number of genes (n=561) were differentially expressed, with a false-discovery rate of ≤5%. Further analyses showed 253 genes differentially expressed within the AA recurrent subgroup and 317 genes in CA recurrent subgroup. In recurrent CRCs, there were 9 genes common to AA and CA patients, suggesting a common gene signature specific for Stage II disease. Canonical pathway analyses and interaction network analyses for these differentially expressed genes revealed that ERK/MAPK, protein kinase A, and CDK5 signaling were the top three affected signaling pathways in recurrent samples from AAs. In contrast, RhoA, integrin, and cell cycle control signaling were the top three affected pathways in Stage II CRCs of CAs. This suggests, for samples from CAs and AAs, a distinct race-based gene expression and downstream effects on pathways.

Conclusion: A common gene expression signature, specific for stage II, together with a race-specific expression profile may have therapeutic implications for AA and CA patients.

Citation Format: Trafina Jadhav, Dongquan Chen, Balananda-Dhurjati Kumar Putcha, Temesgen Samuel, James Posey, Martin Heslin, Upender Manne. Distinct gene expression profile of recurrent stage II colorectal cancers in African American and Caucasian American patients. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4031. doi:10.1158/1538-7445.AM2013-4031

Defining an Embedded Code for Protein Ubiquitination

It has been more than 30 years since the initial report of the discovery of ubiquitin as an 8.5 kDa protein of unknown function expressed universally in living cells. And still, protein modification by covalent conjugation of the ubiquitin molecule is one of the most dynamic posttranslational modifications studied in terms of biochemistry and cell physiology. Ubiquitination plays a central regulatory role in number of eukaryotic cellular processes such as receptor endocytosis, growth-factor signaling, cell-cycle control, transcription, DNA repair, gene silencing, and stress response. Ubiquitin conjugation is a three step concerted action of the E1-E2-E3 enzymes that produces a modified protein. In this review we investigate studies undertaken to identify both ubiquitin and SUMO (small ubiquitin-related modifier) substrates with the goal of understanding how lysine selectivity is achieved. The SUMOylation pathway though distinct from that of ubiquitination, draws many parallels. Based upon the recent findings, we present a model to explain how an individual ubiquitin ligase may target specific lysine residue(s) with the co-operation from a scaffold protein.

Identification of a consensus site for TRAF6/p62 polyubiquitination

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an ubiquitin ligase that regulates a diverse array of physiological processes via forming Lys-63 linked polyubiquitin chains. In this study, the lysine selection process for TRAF6/p62 ubiquitination was examined. The protein sequence of two characterized TRAF6/p62 substrates, NRIF and TrkA, revealed a conserved consensus pattern for the ubiquitination site of these two TRAF6 substrates. The consensus pattern established in the verified substrates was common to the other Trk receptor family members, TrkB and TrkC. Interestingly, Lysine 811 in TrkB was selected for ubiquination, and mutation of Lysine 811 diminished the formation of TRAF6/p62 complex that is necessary for effective ubiquination. Moreover, downstream signaling was affected upon binding of BDNF to the mutant TrkB receptor. These findings reveal a possible selection process for targeting a specific lysine residue by a single E3 ligase and underscore the role of the scaffold, p62, in this process.

Plasma Proteome Database as a resource for proteomics research

Plasma is one of the best studied compartments in the human body and serves as an ideal body fluid for the diagnosis of diseases. This report provides a detailed functional annotation of all the plasma proteins identified to date. In all, gene products encoded by 3778 distinct genes were annotated based on proteins previously published in the literature as plasma proteins and the identification of multiple peptides from proteins under HUPO's Plasma Proteome Project. Our analysis revealed that 51% of these genes encoded more than one protein isoform. All single nucleotide polymorphisms involving protein-coding regions were mapped onto the protein sequences. We found a number of examples of isoform-specific subcellular localization as well as tissue expression. This database is an attempt at comprehensive annotation of a complex subproteome and is available on the web at http://www.plasmaproteomedatabase.org.