Abstract P3-08-11: The prognostic impact of retinoic acid-induced 2 (RAI2) expression in ERα-positive breast cancer patients

Background: Breast cancer cells disseminate to the bone marrow and form bone metastases in a large majority of late-stage patients. Retinoic Acid-Induced 2 (RAI2) was reported as a putative suppressor of early hematogenous dissemination of tumor cells to the bone marrow in breast cancer, particularly in estrogen receptor α (ERα)-positive breast cancer. Here, we investigated mRNA expression of RAI-2 in breast cancer patients during long-term follow-up.

Materials and methods: A total of 451 invasive breast cancer tissues was available for analysis of RAI2 mRNA using a TaqMan PCR system. We also sought correlations between clinicopathological factors and levels of RAI2 expression in these samples. The expression of markers associated with tumor-initiating capacity, such as SNAI1, SNAI2 and VIM was also analyzed. The median follow-up period was 9.0 years. Survival curves were analyzed using the Kaplan-Meier method. Cox proportional hazards regression analysis was used for univariate and multivariate analyses of prognostic values.

Results: We found positive correlations between low expression of RAI2 mRNA and shorter disease-free survival and overall survival in breast cancer patients (P=0.003, P<0.0001, respectively), which was limited to ERα-positive patients (P=0.04, P=0.0009, respectively), and not seen in ERα-negative patients (P=0.52, P=0.27, respectively). Low RAI2 mRNA levels were positively correlated with high grade, ERα-negativity and PgR negativity. Multivariate analysis indicated that low level RAI2 mRNA expression was an independent factor for survival both overall in breast cancer and in ERα-positive breast cancer patients

Multivariate analysis (ERα-positive breast cancer patients)  OS  Multivariate patientsp valueHR(95%CI)Tumor size≤2cm1390.83691 (Reference) >2cm207 1.08(0.54-2.28)Node statusNegative176<0.00011 (Reference) Positive144 4.72(2.33-10.34)Grade11240.95921 (Reference) 2•3218 0.98(0.50-2.14)RAI2 mRNA expressionhigh140<0.00011 (Reference) middle•low206 4.79(2.14-12.78)

.

Conclusion:We show that low expression of RAI2 is an independent factor predictive of a poor prognosis in ERα-positive breast cancer patients. RAI2 could be a promising candidate biomarker and therapeutic target in ERα-positive breast cancer to prevent dissemination to the bone marrow.

Citation Format: Nishikawa S, Kondo N, Endo Y, Hato Y, Hisada T, Nishimoto M, Dong Y, Okuda K, Kato H, Takahashi S, Nakanishi R, Toyama T. The prognostic impact of retinoic acid-induced 2 (RAI2) expression in ERα-positive breast cancer patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-08-11.

Abstract P6-07-34: The prognostic impact of inositol polyphosphate 5-phosphatase PIPP (INPP5J) expression in breast cancer tissue

Background : Inositol polyphosphate 5-phosphatase PIPP (INPP5J) has been identified as a suppressor of oncogenic PI3K/Akt signaling in breast cancer.INPP5J depletion increases transformation and accelerates oncogene-driven tumor growth in vivo, while paradoxically reducing cell migration, invasion, and metastasis. Therefore, we hypothesized that INPP5J gene expression in human breast cancer tissues would be prognostic in early breast cancer patients over long-term follow-up.

Methods: A total of 478 breast cancer tissue samples collected between 2003 and 2008 was available for analysis. We measured INNPP5J mRNA using a TaqMan gene expression assay. PIK3CA mutation status was evaluated using a TaqMan mutation detection assay. We then investigated the correlations of clinicopathological factors and prognosis with levels of INPP5J mRNA and the PIK3CA mutation status.

Results: INPP5J mRNA was expressed at a low level in 30.1% (144/478) and at a medium to high level in the remaining breast cancer samples. Low INPP5J mRNA correlated with larger tumor (p=0.015), high grade (p<0.0001) and, ER-negativity (p<0.0001). PIK3CA mutations were detected in 46% (63/138) of patients analyzed. We found that disease-free survival (DFS) was significantly worse in patients with low levels of INPP5J (p=0.008). Although DFS and INPP5J levels tended to be associated in estrogen receptor (ER)-positive patients (p=0.052), DFS was significantly worse in patients with wild-type PIK3CA and low INPP5J mRNA expression (p=0.008).

Conclusion: We shows that the level of INPP5J mRNA expression is prognostics in breast cancer patients and that its prognostic impact is affected by PIK3CA mutation status.

Citation Format: Kondo N, Kim T-S, Wanifuchi Y, Hato Y, Hisada T, Nishimoto M, Nishikawa S, Toyama T. The prognostic impact of inositol polyphosphate 5-phosphatase PIPP (INPP5J) expression in breast cancer tissue [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-07-34.

Abstract P2-03-07: Exome sequencing of human breast cancer tissues resistant to taxanes

Background: Although taxanes are a mainstay of breast cancer treatment, some cases are resistant to these drugs. This is a crucial issue in breast cancer therapy. In the emerging era of next-generation sequencing, it is possible to obtain extensive genomic information on individual tumors in a very short time. Using this technology, it was reported that specific mutations might affect therapeutic efficacy and induce resistance to specific treatment.

Objective: The aim of this study was to investigate the mechanisms of taxane resistance using whole exon sequencing and expression analyses in human breast cancer tissues.

Materials and Methods: We selected six breast cancer patients whose tumors responded well to anthracycline treatment but suffered disease progression on taxane treatment. We then performed whole exon sequencing on these samples using HiSeq (Illumia). In this way, we identified somatic mutations of candidate genes considered to be instrumental for mediating resistance to taxanes. Next, we performed mRNA expression analyses of these candidate genes in a further 122 breast cancers treated with taxanes at our institute. Finally, we correlated mRNA expression levels of these genes with clinicopathological factors and prognosis.

Results: We identified 9 mutations common to all 6 patients analyzed in this study, and a further 16 mutations shared by 5 of them. Kaplan-Meier analyses showed that high level mRNA expression of 3 of these 25 genes was significantly associated with poorer disease-free survival. Moreover, high level mRNA expression of one of these three genes was significantly associated with worse overall survival. However, there were no significant correlations between expression levels of these three genes and any clinicopathologeical features.

Conclusion: Using next-generation sequencing, we have identified three candidate genes involved in resistance to taxane treatment in breast cancer. We are now analyzing the functional attributes of these three genes.

Citation Format: Endo Y, Dong Y, Kondo N, Hato Y, Hisada T, Nishimoto M, Nishikawa S, Takahashi S, Toyama T. Exome sequencing of human breast cancer tissues resistant to taxanes [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-03-07.

Abstract P5-13-07: Genetic polymorphism of estrogen metabolizing enzyme CYP17A1 rs743572 impacts on serum testosterone level in Japanese premenopausal women

The incidence of breast cancer in Japanese women has doubled in all age groups over the past two decades. We recently demonstrated that this marked increase is mostly due to an increase in the estrogen receptor (ER)-positive subtype, and we created risk prediction models for ER-positive breast cancer in both pre- and post- menopausal women using genetic factors (single nucleotide polymorphism (SNP)), environmental risk factors, serum hormones and growth factors by logistic regression analysis. Serum level of testosterone, which is the precursor of estradiol in estradiol synthesis, was found to be a risk predictor in both pre- and post- menopausal women. On the other hand, it has been reported that some SNPs, including those of estrogen-related genes such as ESR1 and CYP17A1, are correlated with breast cancer risk by genome-wide association studies. To acquire some insights into this mechanism, we analyzed genetic factors (14 SNPs), serum hormones and growth factors (estradiol, testosterone, prolactin, insulin-like growth factor 1 (IGF1) and IGF binding protein 3 (IGFBP3)) in 913 women with breast cancer and 278 disease-free controls for correlation between them.

Serum testosterone and prolactin levels were significantly higher in ER-positive breast cancer patients than in disease-free controls in both pre- (p<0.0001, p<0.0001) and post- (p<0.0001, p = 0.007) menopausal women, and serum estradiol level was significantly higher in ER-positive breast cancer patients than in disease-free controls only in premenopausal women (p = 0.0005). There were significant differences in serum hormone levels among the women with each SNP genotype (homozygotes of major allele, heterozygotes and homozygotes of minor allele), including testosterone among rs743572 genotype (p = 0.014), estradiol among rs827421 genotype (p = 0.016), IGF-1 among rs6905370 genotype (p = 0.032), and prolactin among rs1042522 genotype (p = 0.035) in premenopausal women, as well as estradiol among rs3803662 genotype (p = 0.027) and IGFBP3 among rs6905370 genotype (p = 0.036) in postmenopausal women. In particular, serum testosterone level was significantly different among the rs743572, which is one of the enzymes that convert testosterone to estradiol, of genotypes (AA: 0.308 +/- 0.180 ng/ml, AG: 0.319 +/- 0.193 ng/ml and GG: 0.380 +/- 0.187 ng/ml, p = 0.014). On the other hand, the rs743572 heterozygotes of CYP17A1 have been reported to have increased breast cancer risk than homozygotes of both the major allele and minor allele in premenopausal women. Further studies are required to clarify this mechanism.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-13-07.

Abstract P5-05-04: Relationship between plasma estradiol levels and estrogen-regulated gene expressions in premenopausal estrogen receptor-positive breast cancers

Background: Estrogen receptor (ER) and progesterone receptor (PgR) expression status in breast cancer are important factors in determining the use of adjuvant therapy. Plasma estradiol (E2) and progesterone vary markedly through the menstrual cycle. Recently, the levels of PgR expression were reported to be correlated with E2 at the time of surgery in Caucasian premenopausal breast cancer patients. Materials and methods: In this study, plasma E2 levels at surgery were examined for correlations with expressions of estrogen-regulated genes (ERGs), including PgR, and proliferation genes in 147 Japanese premenopausal ER-positive breast cancers. Plasma E2 and progesterone, FSH, and LH were measured on the day of surgery by ECLIA and mRNA expressions were analyzed for 4 ERGs (PgR, GREB1, TFF1, PDZK1), 2 progesterone-regulated (RANKL, cyclin D1) and 2 proliferation genes (MKI67, BIRC5) by RT-PCR using the TaqMan system. ER and PgR protein expression levels were estimated by immunohistochemistry. Results: Our results revealed that expressions of PgR mRNA and protein in breast cancer tissues were significantly correlated with plasma E2 levels at surgery (p = 0.005, p = 0.0165, respectively). Other ERGs were also significantly correlated with plasma E2 levels. However, there were no correlations between mRNA expressions of proliferation genes, MKI67 and BIRC5, and plasma E2 levels. Furthermore, mRNA expressions of the progesterone-regulated genes, RANKL and cyclin D1, were significantly correlated with PgR mRNA expression (p<0.0001, p<0.0001, respectively). Discussion: Significant correlations were seen in the expression of ERGs in Japanese ER-positive breast cancers according to the plasma E2 levels, which vary markedly through the menstrual cycle. Our results supported the previous report in Caucasian patients by other group. This variability may affect the interpretation of gene expression profiles incorporating ERGs such as the 21-gene recurrence score.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-05-04.

Crystal structures of modified myoglobins. I. Heme orientation and structural changes around heme in myoglobins reconstituted with isopemptoheme, pemptoheme, 2-ethyldeuteroheme, and 4-ethyldeuteroheme

The crystal structures of sperm whale metmyoglobins reconstituted with four modified hemes, isopemptoheme, pemptoheme, 2-ethyldeuteroheme, and 4-ethyldeuteroheme, have been determined and refined at 2.2 A resolution to R = 0.217, 0.218, 0.213, and 0.222, respectively. All the crystals of these myoglobins are isomorphous with that of native metmyoglobin. The structural changes of the modified myoglobin from the native myoglobin were examined on difference Fourier maps; the orientation of 4-ethyldeuteroheme in the heme pocket is such that the heme is rotated by 180 degrees about an axis through the alpha-gamma-meso carbons, whereas the orientations of the other three hemes are the same as that of the protoheme in the native myoglobin. The changes of the structures around the heme become greater in the order of isopemptoheme, 2-ethyldeuteroheme less than pemptoheme less than 4-ethyldeuteroheme. The magnitudes of the changes seem to be related to the oxygen affinities of these four reconstituted myoglobins.

Crystal structures of modified myoglobins. II. Relation between oxygen affinity properties and structural changes around heme in myoglobins reconstituted with 2,4-diisopropyldeuteroheme, 2-isopropyl-4-vinyldeuteroheme, and 2-vinyl-4-isopropyldeuteroheme

The crystal structures of sperm whale metmyoglobins reconstituted with three kinds of modified hemes, 2,4-diisopropyldeuteroheme, 2-isopropyl-4-vinyldeuteroheme, and 2-vinyl-4-isopropyldeuteroheme, have been determined and refined at 2.2 A resolution to R = 0.216, 0.219, and 0.195, respectively. All the crystals of these myoglobins are isomorphous with that of native metmyoglobin. The 2-vinyl-4-isopropyldeuteroheme was found to be in a reverse orientation, in which the heme plane is rotated by 180 degrees about an axis through the alpha-gamma-meso carbons, whereas the orientations of the other two hemes were the same as that of protoheme in native myoglobin. In the myoglobins with 2,4-diisopropyldeuteroheme and 2-vinyl-4-isopropyldeuteroheme, both of which have lower oxygen affinities than native myoglobin, the bulky isopropyl side chain pushes Phe 43 0.7 A toward His 64 (the distal histidine) in the former, and the whole E helix at most 1.5 A, including a 0.7 A shift of the His 64 imidazole ring, in the latter. The changes of the structures prevent His 64 from forming a hydrogen bond with the liganded oxygen molecule, so that these two modified myoglobins show low oxygen affinities. On the other hand, there is no such drastic displacement in myoglobin with 2-isopropyl-4-vinyldeuteroheme, which has a slightly higher oxygen affinity than native myoglobin.