Microsatellite Instability in Korean Patients with Gastric Adenocarcinoma

Article information

Korean J Intern Med. 1997;12(2):144-154
Department of Internal Medicine, Chonnam University Medical School, Kwangju, Korea
*Department of Internal Pathology, Chonnam University Medical School, Kwangju, Korea
**Chonnam University Medical School, Presbyterian Medical Center, Kwangju, Korea
Address reprint requests to: Chong Mann Yoon, M.D., Department of Internal Medicine, Chonnam University Hospital, 8 Hakdong, Dongku, Kwangju, 501-757, Korea

Abstract

Objectives

Microsatellites are short repeated oligonucleotide sequences found throughout the human genome. High mutation rates in microsatellite sequences have been found in tumors from patients with hereditary non-polyposis colorectal carcinoma and some sporadic carcinomas. However, little information is available regarding RER-positive phenotype in gastric carcinomas, particularly in terms of age of onset and other pathologic features, such as histologic types, degree of differentiation, location or stage of the carcinoma.

Methods

To obtain a better understanding of the molecular mechanism of gastric carcinogenesis, microsatellite instability was examined at 6 gene loci (D2S71, D2S119, D3S1067, D6S87, D8S87, D11S905) in 77 gastric carcinomas (40 cases of young patients and 37 cases of elderly patients).

Results

RER-positive phenotypes were found in 17 (22.1%) of 77 cases. In young patients (under 40 years) RER-positive phenotype was found in 9 (22.5%) of 40 cases, and in elderly patients 8 (21.6%) of 37 cases. Moderately differentiated carcinoma revealed a significantly high frequency of RER-positive phenotype than well differentiated carcinoma (p<0.001). Tumors arising from the middle third (p<0.001) or lower third (p<0.001) revealed higher frequency of RER-positive phenotype than the tumors arising from the upper third of the stomach. The RER-positive phenotype was not significantly affected by the sex, histologic type or stage of carcinoma.

Conclusion

RER-positive phenotype occurs frequently in gastric carcinoma, although the frequency of RER-positive phenotype between young and elderly patient was not significantly different. Thus, the acquisition of RER-positive phenotype might be an early event in gastric carcinogenesis.

INTRODUCTION

Microsatellite is a tandem array of short stretches of nucleotide sequences, usually repeated between 15 and 30 times1,2). These regions of genome tend to be polymorphic or variable among individuals. Recently, abnormalities of such repeats have been implicated in the genesis of hereditary non-polyposis colorectal cancer (HNPCC). In HNPCC kindreds, linkage to the marker D2S123 on chromosome 2p was reported, and it was simultaneously noted that instability of the microsatellite repeat number was present in microsatellites scattered throughout the genome3,4). It was suggested that the mutation affecting DNA replication or repair predisposed to replication errors. Candidate gene of mismatch repair in gene hMSH2 was identified and shown to be a DNA mismatch binding protein5,6). Subsequently, additional mismatch repair genes were shown to be involved in the pathogenesis of HNPCC, comprising hMLH1, hPMS1, and hPM27,8). Analysis of sporadic tumors belonging to the HNPCC spectrum (colorectal carcinoma, endometrial carcinoma and gastric carcinoma) revealed a significant proportion of cases with multiple replication errors, as in HNPCC cases9). In contrast, other sporadic tumors (lung, breast, testis, CNS tumors and soft tissue sarcomas) showed microsatellite instability (MI) as a rare event10). Recent reports show that cases of small cell carcinoma of the lung, cases with multiple primary tumors and late stage chronic myelocytic leukemia may be associated with replication error (RER)-positive phenotype1113). Presumably, it has undergone a germ line mutation of mismatch repair genes in HNPCC; similarly somatic mutations of mismatch repair genes are presumed to have occurred in the tumors of some sporadic colon cancer14).

Gastric adenocarcinoma is one of the most common malignancies in the world, especially in Korea. Although the molecular basis of the development of gastric carcinoma remains unclear, there have been many attempts to apply the same analysis which has been effective in identifying the oncogenesis of colon cancer15,16). However, little information is available regarding RER-positive phenotype in gastric carcinomas, particularly in terms of age of onset (gastric carcinoma of the young vs. elderly patient) and other pathologic features such as histologic types, degree of differentiation, location, and stage of the carcinoma. Gastric carcinoma of the young adult is characterized by mostly diffuse (by Lauren’s criteria17) or signet-ring cell type (by WHO criteria18), poorly differentiated adenocarcinoma without adjacent intestinal metaplasia, and high incidence of family history of gastric carcinoma1921). In order to obtain a better understanding of the molecular mechanism of gastric carcinogenesis, microsatellite instability was examined at 6 gene loci in 77 gastric carcinomas (40 cases of young patients and 37 cases of elderly patients).

MATERIALS AND METHODS

1. Materials

Forty cases of subtotal or total gastrectomy specimens received at the Department of Pathology of Chonnam University Hospital (69 cases) and Presbyterian Medical Center (8 cases), which were diagnosed as primary adenocarcinoma of stomach in the interval of January 1, 1990 to May 1, 1996, were selected. The adenocarcinomas were classified according to the WHO criteria18), and clinicopathological data were collected from the review of medical records (Table 1). Males were 42 cases, and females were 35 cases. Tubular adenocarcinoma was 36, signet-ring cell type was 36 and mucinous type was 5 cases; well differentiated adenocarcinoma was 6, moderately differentiated was 21 and poorly differentiated was 50 cases. Four cases were located in the upper third of the stomach (cardia and fundus), 25 cases in the middle third (body) and 30 cases in the lower third (antrum and pylorus). Twelve cases were located in two different areas, and 6 cases were undetermined. Stage Ia was 13 cases, Ib 9, II 13, IIIa 13, IIIb 5, and IV 18. Stages were undetermined in 6 cases.

Clinicopathologic Data of the Gastric Carcinoma

2. DNA isolation from the tissue

A hematoxylin-eosin stained tissue section from each block was used to determine the area of highest tumor cellularity for DNA preparation. One or more tissue plugs were then removed from each block, minced with a razor blade and deparaffinized with a series of rinses in xylene and ethanol. The tissue was digested completely in TE buffer (pH 8.0), containing 400 μg/ml of proteinase K replenished daily and 0.5% sodium dodecyl sulfate, for 3–4 days at 54°C. Following a standard series of phenol, phenol/chloroform and chloroform extractions, the DNA was ethanol-precipitated, washed in 70% ethanol, resuspended in TE buffer (pH 8.0) and stored at −20°C.

3. PCR analysis at microsatellite loci

The primers used to examine the microsatellite loci were: D2S71, D2S119 (AFM077yb7)22), D3S106723), D6S87 (MFD47)24), D8S87 (MFD39)25), and D11S905 (AFM105xb10)22). The PCR was performed in 10μl volumes of a mixture containing 1x PCR buffer [10mmol Tris-HCI, pH 8.8, 1.5mmol MgCl2, 50 mmol KCI, 0.1% Triton X-100], 10pmol of unlabeled primer and 5pmol of labeled primer with [γ-32p]ATP(>5,000ci/mmol), 50ng DNA, 0.1 units Taq DNA polymerase, 125μmol of each deoxynucleotide. Reaction mixtures were heated to 95°C for 5 min and cycled 32 times; each cycle consisted of 1 min at 94°C, 1 min at 52–58°C, 1 min at 72°C for strand elongation. After that, heated for 10 min at 72°C for the final elongation using a PCR machine (Model 480, Perkin Elmer Cetus, Norwalk, CT, USA). Following PCR, 3μl of reaction product was denatured and then electrophoresed in 6% polyacrylamide gels containing 8 mol urea. After electrophoresis, the gels were exposed to X-ray film for 3–6 h at −70°C.

4. Interpretation of PCR results

Microsatellite instability (MI) was evident when the tumor DNAs gained new bands compared to their normal counterparts (Fig. 1A, B). If at least one locus revealed MI, the case was regarded as RER-positive (Table 2). Deletion of band (loss of heterozygosity of microsatellite allele) was not considered to be a microsatellite alteration in the present study.

Fig. 1.

Analysis of genetic instability in paired normal (N) and tumor (T) DNA at loci D2S71 of J21 patient (A), and D8S87 of O29 and O28 patients (B). At tumor DNAs, abnormal patterns indicating expansion are shown at each microsatelite locus. Normal alleles appear as major bands with their ladders. Patient numbers are shown above the lanes.

MI(+); microsatellite-positive, MI(−); microsatellite-negative

Summary of Microsatellite Instability of the Gastric Carcinoma

RESULTS

Table 2 summarizes results of PCR analyses in 40 cases of the gastric carcinoma in young adult and 37 cases in elderly. Fig. 1A shows typical MI of young adult (J21) and Fig. 1B reveals heterozygosity (O28) and MI (O29) from elderly patients.

Out of 77 cases of gastric carcinoma, 17 cases (22.1%) were RER-positive and 60 cases (77.9%) were RER-negative. Nine cases (22.5%) out of 40 young adult cases were RER-positive and 8 (21.6%) out of 37 elderly patients were RER-positive (Table 3A). Seven (16.7%) out of 42 male cases revealed RER-positive phenotype, and 10 (28.6%) out of 35 female cases showed RER-positive phenotype. There was no difference in RER-positivity between the male and female patients by logistic regression analysis (Table 3B). Ten (27.8%) out of 36 tubular type, 6 (16.7%) out of 36 signet-ring cell carcinoma and 1 (20.0%) out of 5 mucinous carcinoma were RER-positive phenotype (Table 3C).

Frequency of RER-positive and Negative Phenotypes in Young and Elderly Gastric Adenocarcinoma Patients

Frequency of RER-positive and Negative Phenotypes in Male and Female Gastric Adenocarcinoma Patients

Frequency of RER-positive and Negative Phenotypes According to the Histologic Types of Gastric Adenocarcinoma Patients

One (16.7%) out of 6 well differentiated carcinoma was RER-positive, whereas 28.6% (6/21) of moderately differentiated carcinoma and 20.0% (10/50) of poorly differentiated carcinoma were RER-positive (Table 3D). Moderately differentiated carcinoma revealed higher frequency of RER-positive phenotypes than well differentiated carcinoma (p<0.01; by logistic regression analysis).

Frequency of RER-positive and Negative Phenotypes According to the Differentiation of Gastric Adenocarcinoma Patients

None of the tumors located in the upper third of the stomach (cardia and fundus) were RER-positive, while 16.0% (4/25) of the tumors located in the middle third (body) and 26.7% (8/30) of the tumors located in the lower third (antrum and pylorus) was RER-positive. The frequency of RER-positive cases arising from the middle (p<0.001) and lower third (p<0.0001) of the stomach was significantly higher than the tumor arising from the upper third (by logistic regression analysis) (Table 3E).

Frequency of RER-positive and Negative Phenotypes According to the Location of Gastric Adenocarcinoma

Percentage of RER-positive cases was 15.4% (2/13) in stage IA, 11.1% (1/9) in stage IB, 7.7% (1/13) in stage II, 53.8% (7/13) in stage IIIA, 0% (0/5) in stage IIIB and 22.2% (4/18) in stage IV, respectively, by logistic regression analysis (Table 3F).

Frequency of RER-positive and Negative Phenotypes According to the Stages of Gastric Adenocarcinoma

DISCUSSION

It has been demonstrated that the expression of several oncogenes and the mutation of tumor suppressor genes may vary according to histologic types of gastric carcinoma and affect the biologic behavior of gastric carcinoma26,27). Recently, RER-positive phenotypes have also occurred in sporadic gastric carcinoma and played a role in tumor progression. The frequency of RER-positive phenotype ranges from 15% to 38.5%2832). The frequency of RER-positive phenotype of this study was 22.1%, when six chromosomal loci were examined. This suggests that RER-positive phenotype is important in some portion of gastric carcinogenesis.

Gastric carcinoma of the young adult is characterized by mostly diffuse (by Lauren’s criteria17) or signet–ring cell type (by WHO criteria18), poorly differentiated adenocarcinoma without adjacent intestinal metaplasia and high incidence of family history of gastric carcinoma1921). In the present study, the frequency of RER-positive phenotype in young patients was 22.5% compared to the 21.6% in elderly patients. When the other factors (such as sex, histologic type, degree of differentiation, location and stage) are considered, there is no significant difference of RER-positive phenotype between the two groups.

Tumors arising from the middle or lower third of the stomach revealed higher frequency of RER-positive phenotype than the tumors from the upper third (cardia and fundus). This finding supports the hypothesis that instability is tissue specific, as proximal colon carcinoma reveals higher frequency of RER-positive phenotype than distal colon carcinomas33,34). RER-positive frequency was not affected by the histologic types, although tubular type and signet-ring cell carcinomas reveal relatively high frequency of RER-positivity compared with mucinous type. Moderately differentiated carcinoma revealed higher frequency of RER-positivity compared to the well differentiated carcinoma. Han et al28) reported that poorly differentiated carcinoma reveal a higher frequency of RER-positive phenotype than well differentiated one.

The result reveals that there is no difference of RER-positive phenotypes in the tumors of different stages. Even the carcinomas confined in the lamina propria (stage Ia) reveal 15.5% (2 out of 13 cases) RER-positive phenotype. Palmirotta et al.35) found that 50% of early gastric carcinomas are RER-positive when they analyzed at 11 microsatellite markers. Semba et al.36) found RER-positive phenotypes in 33% of mucosa of intestinal metaplasia, 42% of gastric adenoma and 33% of gastric carcinoma. These findings suggest that RER-positive phenotype would occur at the early stage of gastric carcinogenesis. Conversely, Chong et al.30) reported that frequency of RER-positive phenotype is significantly higher in advanced gastric carcinoma than in early gastric carcinoma (33.3% vs. 12.0%).

In conclusion, RER-positive phenotype occurs frequently in gastric carcinoma, and is tissue specific. But, there is no difference in RER-positive phenotypes between the young and elderly gastric carcinoma patients. The acquisition of RER-positive phenotype might be an early event in gastric carcinogenesis.

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Article information Continued

Fig. 1.

Analysis of genetic instability in paired normal (N) and tumor (T) DNA at loci D2S71 of J21 patient (A), and D8S87 of O29 and O28 patients (B). At tumor DNAs, abnormal patterns indicating expansion are shown at each microsatelite locus. Normal alleles appear as major bands with their ladders. Patient numbers are shown above the lanes.

MI(+); microsatellite-positive, MI(−); microsatellite-negative

Table 1.

Clinicopathologic Data of the Gastric Carcinoma

Number Age Sex Type Grade Location Stage
J01 32 F signet–ring PD MIDDLE 1/3 IA
J02 27 M tubular PD COMBINED IV
J03 33 F signet–ring PD MIDDLE 1/3 IA
J04 31 M signet–ring PD MIDDLE 1/3 IIIA
J05 28 M signet–ring PD MIDDLE 1/3 IA
J06 28 M signet–ring PD COMBINED IIIB
J07 33 M signet–ring PD LOWER 1/3 IB
J08 28 F signet–ring PD MIDDLE 1/3 IB
J09 36 M signet–ring PD COMBINED IV
J10 34 M tubular PD LOWER 1/3 IA
J11 36 F tubular MD UPPER 1/3 II
J12 35 F signet–ring PD MIDDLE 1/3 IV
J13 35 F tubular WD COMBINED IV
J14 37 F signet–ring PD MIDDLE 1/3 IIIA
J15 36 M signet–ring PD MIDDLE 1/3 IA
J16 31 M tubular PD MIDDLE 1/3 IB
J17 35 F signet–ring PD UD II
J18 28 M signet–ring PD MIDDLE 1/3 UD
J19 35 F signet–ring PD MIDDLE 1/3 IB
J20 36 F signet–ring PD MIDDLE 1/3 IV
J22 26 M signet–ring PD LOWER 1/3 IV
J23 29 F signet–ring PD UPPER 1/3 IV
J24 32 F signet–ring PD COMBINED IA
J25 33 M signet–ring PD UD UD
J26 31 M tubular PD LOWER 1/3 IV
J27 31 M tubular PD UD UD
J28 30 M tubular PD LOWER 1/3 IIIA
J30 33 F signet–ring PD MIDDLE 1/3 IB
J31 31 M signet–ring PD UD IV
J32 33 F mucinous PD COMBINED IIIA
J33 35 M signet–ring PD MIDDLE 1/3 IA
J34 35 F tubular PD COMBINED IV
J35 33 M signet–ring PD LOWER 1/3 IV
J36 35 F tubular MD MIDDLE 1/3 IV
J37 19 M signet–ring PD UD UD
J38 27 F tubular PD LOWER 1/3 IIIA
J39 35 F signet–ring PD LOWER 1/3 IIIB
J40 30 F tubular PD LOWER 1/3 IV
J41 33 M signet–rin WD COMBINED IV
J42 31 F signet–ring PD MIDDLE 1/3 IIIA
O01 62 F tubular PD MIDDLE 1/3 IA
O02 62 F signet–ring PD LOWER 1/3 IIIA
O03 64 F tubular PD LOWER 1/3 II
O04 60 M tubular MD MIDDLE 1/3 IIIA
O05 72 M tubular MD LOWER 1/3 UD
O06 59 M tubular MD LOWER 1/3 II
O07 59 M tubular MD LOWER 1/3 II
O08 61 M tubular PD LOWER 1/3 IB
O09 55 F tubular MD LOWER 1/3 IV
O10 55 M tubular WD UPPER 1/3 IA
O11 69 F tubular PD LOWER 1/3 IB
O12 69 M tubular PD MIDDLE 1/3 IV
O14 58 F tubular WD LOWER 1/3 II
O15 65 M tubular MD LOWER 1/3 IIIA
O16 71 F tubular MD MIDDLE 1/3 IB
O17 62 F tubular MD LOWER 1/3 IIIA
O18 50 M tubular MD LOWER 1/3 IIIA
O19 67 M tubular MD LOWER 1/3 IA
O20 57 M tubular WD MIDDLE 1/3 IV
O21 75 F tubular MD COMBINED II
O22 60 F tubular PD LOWER 1/33 IIIB
O23 51 M tubular MD MIDDLE 1/3 IIIB
O24 58 M signet–ring PD LOWER 1/3 II
O25 65 M signet–ring PD MIDDLE 1/3 II
O26 66 F tubular MD UPPER 1/3 IIIA
O27 86 M signet–ring PD LOWER 1/3 IIIB
O28 54 M signet–ring PD LOWER 1/3 IA
O29 50 M mucinous MD COMBINED II
O30 74 M mucinous MD LOWER 1/3 II
O31 55 F tubular MD LOWER 1/3 IIIA
O32 62 F signet–ring PD UD UD
O33 56 M signet–ring PD COMBINED IB
O34 50 F signet–ring MD LOWER 1/3 II
O37 67 F mucinous PD LOWER 1/3 IA
O38 56 M mucinous MD COMBINED IV
O39 68 M signet–ring PD MIDDLE 1/3 IA
O40 68 M tubular WD MIDDLE 1/3 II

WD, well differentiated; MD, moderately differentiated; PD, poorly differentiated, upper 1/3, cardia and fundus; middle 1/3, body; lower 1/3, pylorus and antrum. UD, undetermined. Combined tumors are located in more than 2 different locations

Table 2.

Summary of Microsatellite Instability of the Gastric Carcinoma

No D2S71 D2S119 D3S1067 D6S87 D8S87 D11S905 RER
J01
J02 + + + + +
J03 + + + + +
J04 + ND +
J05
J06
J07
J08
J09
J10
J11
J12
J13 ND ND + +
J14
J15
J16
J17
J18
J19
J20 ND
J22 ND ND
J23 ND
J24 + + + ND + +
J25 + + + +
J26 + ND ND +
J27
J28 ND
J30
J31
J32 ND
J33
J34
J35 ND +
J36 + + +
J37 +
J38 +
J39
J40
J41
J42 ND ND
O01
O02 + ND + ND +
O03
O04 + +
O05
O06 ND
O07
O08 ND ND
O09 ND ND
O10
O11 + ND + ND +
O12 ND ND ND
O14 ND ND
O15 + +
O16
O17 + + + +
O18 ND
O19
O20 ND ND
O21 ND
O22 ND ND
O23
O24 ND
O25
O26 ND
O27 ND ND
O28
O29
O30 ND + +
O31 + +
O32 + +
O33 ND ND ND
O34 ND ND ND
O37 ND
O38
O39 ND ND ND
O40

+ : positive for MI, −: negatiVe for MI, NO: not done

Table 3A.

Frequency of RER-positive and Negative Phenotypes in Young and Elderly Gastric Adenocarcinoma Patients

Categories RER phenotype
Total %#1 Positive %#2 Negative %#3
Young 51.9% (40/77) 22.5% (9/40) 77.5% (31/40)
Elderly 48.1% (37/77) 21.6% (8/37) 78.4% (29/37)
Total 100% (77/77) 22.1% (17/77) 77.9% (60/77)
#1

Number of subgroup cases/number of total cases.

#2

Number of RER-positive cases/number of subgroup cases.

#3

Number of RER-negative cases/number of subgroup cases

Table 3B.

Frequency of RER-positive and Negative Phenotypes in Male and Female Gastric Adenocarcinoma Patients

Categories RER phenotype
Total %#1 Positive %#2 Negative %#3
Male 54.5% (42/77) 16.7% (7/42) 83.3% (35/42)
Female 45.5% (35/77) 28.6% (10/35) 71.4% (25/35)
Total 100% (77/77) 22.1% (17/77) 77.9% (60/77)
#1

Number of subgroup cases/number of total cases.

#2

Number of RER-positive cases/number of subgroup cases.

#3

Number of RER-negative cases/number of subgroup cases.

Table 3C.

Frequency of RER-positive and Negative Phenotypes According to the Histologic Types of Gastric Adenocarcinoma Patients

Categories RER phenotype
Total %#1 Positive %#2 Negative %#3
Tubular 46.8% (36/77) 27.8% (10/36) 72.2% (26/36)
Signet–ring 46.8% (36/77) 16.7% (6/36) 83.3% (30/36)
Mucinous 6.5% (5/77) 20.0% (1/5) 80.0% (4/5)
Total 100% (77/77) 22.1% (17/77) 77.9% (60/77)
#1

Number of subgroup cases/number of total cases.

#2

Number of RER-positive cases/number of subgroup cases.

#3

Number of RER-negative cases/number of subgroup cases.

Table 3D.

Frequency of RER-positive and Negative Phenotypes According to the Differentiation of Gastric Adenocarcinoma Patients

Categories RER phenotype
Total %#1 Positive %#2 Negative %#3
WD 7.8% (6/77) 16.7% (1/6) 83.3% (5/6)
MD 27.3% (21/77) 28.6% (10/35)* 71.4% (15/21)
PD 61.9% (50/77) 20.0% (10/50) 80.0% (40/50)
Total 100% (77/77) 22.1% (17/77) 77.9% (60/77)
#1

Number of subgroup cases/number of total cases.

#2

Number of RER-positive cases/number of subgroup cases.

#3

Number of RER-negative cases/number of subgroup cases.

WD, well differentiated adenocarcinoma; MD, moderately differentiated adenocarcinoma; PD, poorly differentiated adenocarcinoma.

*

Statistically different (higher ratio) than WD (p<0.001).

Table 3E.

Frequency of RER-positive and Negative Phenotypes According to the Location of Gastric Adenocarcinoma

Categories RER phenotype
Total %#1 Positive %#2 Negative %#3
Upper third 6.8% (4/59) 0% (0/4) 100% (4/4)
Middle third 42.4% (25/59) 16.0% (4/25)* 84.0% (21/25)
Lower third 50.8% (30/59) 26.7% (8/30)* 73.3% (22/30)
Total 100% (77/77) 20.3% (12/59) 79.7% (47/59)
#1

Number of subgroup cases/number of total cases.

#2

Number of RER-positive cases/number of subgroup cases.

#3

Number of RER-negative cases/number of subgroup cases.

Upper third, cardia and fundus; middle third, body; lower third, antrum and pylorus.

*

Statistically different (higher) ratio than that of upper third (p< 0.001).

Table 3F.

Frequency of RER-positive and Negative Phenotypes According to the Stages of Gastric Adenocarcinoma

Categories RER phenotype
Total %#1 Positive %#2 Negative %#3
IA 18.3% (13/71) 15.4% (2/13) 84.6% (11/13)
IB 12.6% (9/71) 11.1% (1/9) 88.9% (8/9)
II 18.3% (13/71) 7.7% (1/13) 92.3% (12/13)
IIIA 18.3% (13/71) 53.8% (7/13) 46.2% (6/13)
IIIB 7.0% (5/71) 0% (0/5) 100% (5/5)
IV 25.4% (18/71) 22.2% (4/18) 77.8% (14/18)
Total 100% (71/71) 21.1% (15/71) 78.9% (56/71)
#1

Number of subgroup cases/number of total cases.

#2

Number of RER-positive cases/number of subgroup cases.

#3

Number of RER-negative cases/number of subgroup cases.