Correlation between miRseq expression and clinical features
Overview
Introduction

This pipeline uses various statistical tests to identify miRs whose log2 expression levels correlated to selected clinical features.

Summary

Testing the association between 502 miRs and 4 clinical features across 113 samples, statistically thresholded by P value < 0.05 and Q value < 0.3, 3 clinical features related to at least one miRs.

  • 4 miRs correlated to 'Time to Death'.

    • HSA-MIR-361 ,  HSA-MIR-421 ,  HSA-MIR-17 ,  HSA-MIR-20A

  • 2 miRs correlated to 'AGE'.

    • HSA-MIR-589 ,  HSA-MIR-148B

  • 1 miR correlated to 'GENDER'.

    • HSA-MIR-106A

  • No miRs correlated to 'RACE'

Results
Overview of the results

Complete statistical result table is provided in Supplement Table 1

Table 1.  Get Full Table This table shows the clinical features, statistical methods used, and the number of miRs that are significantly associated with each clinical feature at P value < 0.05 and Q value < 0.3.

Clinical feature Statistical test Significant miRs Associated with                 Associated with
Time to Death Cox regression test N=4 shorter survival N=4 longer survival N=0
AGE Spearman correlation test N=2 older N=2 younger N=0
GENDER Wilcoxon test N=1 male N=1 female N=0
RACE Kruskal-Wallis test   N=0        
Clinical variable #1: 'Time to Death'

4 miRs related to 'Time to Death'.

Table S1.  Basic characteristics of clinical feature: 'Time to Death'

Time to Death Duration (Months) 0.1-143.4 (median=17.8)
  censored N = 77
  death N = 36
     
  Significant markers N = 4
  associated with shorter survival 4
  associated with longer survival 0
List of 4 miRs differentially expressed by 'Time to Death'

Table S2.  Get Full Table List of 4 miRs significantly associated with 'Time to Death' by Cox regression test

HazardRatio Wald_P Q C_index
HSA-MIR-361 2 2.353e-05 0.012 0.716
HSA-MIR-421 2.1 3.255e-05 0.016 0.732
HSA-MIR-17 1.89 0.0002944 0.15 0.684
HSA-MIR-20A 1.82 0.0004464 0.22 0.683
Clinical variable #2: 'AGE'

2 miRs related to 'AGE'.

Table S3.  Basic characteristics of clinical feature: 'AGE'

AGE Mean (SD) 61.3 (14)
  Significant markers N = 2
  pos. correlated 2
  neg. correlated 0
List of 2 miRs differentially expressed by 'AGE'

Table S4.  Get Full Table List of 2 miRs significantly correlated to 'AGE' by Spearman correlation test

SpearmanCorr corrP Q
HSA-MIR-589 0.3336 0.0003047 0.153
HSA-MIR-148B 0.3316 0.0003342 0.167
Clinical variable #3: 'GENDER'

One miR related to 'GENDER'.

Table S5.  Basic characteristics of clinical feature: 'GENDER'

GENDER Labels N
  FEMALE 61
  MALE 52
     
  Significant markers N = 1
  Higher in MALE 1
  Higher in FEMALE 0
List of one miR differentially expressed by 'GENDER'

Table S6.  Get Full Table List of one miR differentially expressed by 'GENDER'. 0 significant gene(s) located in sex chromosomes is(are) filtered out.

W(pos if higher in 'MALE') wilcoxontestP Q AUC
HSA-MIR-106A 885 5.452e-05 0.0274 0.721
Clinical variable #4: 'RACE'

No miR related to 'RACE'.

Table S7.  Basic characteristics of clinical feature: 'RACE'

RACE Labels N
  ASIAN 4
  BLACK OR AFRICAN AMERICAN 8
  WHITE 77
     
  Significant markers N = 0
Methods & Data
Input

  • Expresson data file = SARC-TP.miRseq_RPKM_log2.txt

  • Clinical data file = SARC-TP.merged_data.txt

  • Number of patients = 113

  • Number of miRs = 502

  • Number of clinical features = 4

Survival analysis

For survival clinical features, Wald's test in univariate Cox regression analysis with proportional hazards model (Andersen and Gill 1982) was used to estimate the P values using the 'coxph' function in R. Kaplan-Meier survival curves were plot using the four quartile subgroups of patients based on expression levels

Correlation analysis

For continuous numerical clinical features, Spearman's rank correlation coefficients (Spearman 1904) and two-tailed P values were estimated using 'cor.test' function in R

Student's t-test analysis

For two-class clinical features, two-tailed Student's t test with unequal variance (Lehmann and Romano 2005) was applied to compare the log2-expression levels between the two clinical classes using 't.test' function in R

ANOVA analysis

For multi-class clinical features (ordinal or nominal), one-way analysis of variance (Howell 2002) was applied to compare the log2-expression levels between different clinical classes using 'anova' function in R

Q value calculation

For multiple hypothesis correction, Q value is the False Discovery Rate (FDR) analogue of the P value (Benjamini and Hochberg 1995), defined as the minimum FDR at which the test may be called significant. We used the 'Benjamini and Hochberg' method of 'p.adjust' function in R to convert P values into Q values.

References
[1] Andersen and Gill, Cox's regression model for counting processes, a large sample study, Annals of Statistics 10(4):1100-1120 (1982)
[2] Spearman, C, The proof and measurement of association between two things, Amer. J. Psychol 15:72-101 (1904)
[3] Lehmann and Romano, Testing Statistical Hypotheses (3E ed.), New York: Springer. ISBN 0387988645 (2005)
[4] Howell, D, Statistical Methods for Psychology. (5th ed.), Duxbury Press:324-5 (2002)
[5] Benjamini and Hochberg, Controlling the false discovery rate: a practical and powerful approach to multiple testing, Journal of the Royal Statistical Society Series B 59:289-300 (1995)
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