Breast cancer patient characteristics related to HER2 status from cBioPortal.
To analyze the association between VDR and HER2 in BC, we obtained a total of 1904 BC patients with clinical prognosis characteristics, gene expression level, and CNA data from cBioPortal [41]. Measuring the association between expression/CNA of VDR/HER2 and patients’ characteristics can determine the combined effects of VDR and HER2 in BC diagnosis and prognosis. The determined characteristics were divided into two groups: those related (Table 1) and unrelated (Table S1) to HER2 status. In this dataset, 236 (12.39%) patients were HER2+, which is important for deciding between HER2-targeted therapies or drugs, and 417 (21.95%) patients gained HER2 amplification status measured by SNP6 (Table 1). Other genes, such as claudins and hormone receptors, can also represent useful diagnostics and prognostics related to HER2 status in BC [14, 42]. In this dataset, 220 (11.55%) patients were identified as HER2 + in the claudin subtype, while 188 (11.06%) patients were classified into HER2 + in a three-gene model (Table 1).
Table 1
Clinical characteristics related to HER2 status of breast cancer patients with mRNA expression data from cBioPortal.
Clinical characteristic (number) | Number | % |
HER2 status (1904) | | |
Negative | 1668 | 87.61 |
Positive | 236 | 12.39 |
HER2 SNP6 (1900) | | |
Gain | 417 | 21.95 |
Loss | 100 | 5.26 |
Neutral | 1383 | 72.79 |
Claudin subtype (1904) | | |
Basal | 199 | 10.45 |
claudin-low | 199 | 10.45 |
Her2 | 220 | 11.55 |
LumA | 679 | 35.66 |
LumB | 461 | 24.21 |
NC | 6 | 0.32 |
Normal | 140 | 7.35 |
Three-gene (1700) | | |
ER-/HER2- | 290 | 17.06 |
ER+/HER2- High Prolif | 603 | 35.47 |
ER+/HER2- Low Prolif | 619 | 36.41 |
HER2+ | 188 | 11.06 |
As listed in Table S1, 15 clinical characteristics unrelated to HER2 status also depict the basic information of patients with BC progression. The median age of these patients was 61.77 years, ranging from 21.93 − 96.29 years. Among these cases, 9.01%, 40.30%, and 50.60% were in tumor Grade 1, 2, and 3, respectively, and most were in Stage 1 (33.86%) and Stage 2 (57.02%). The tumors have a size of 23, with a range of 1 − 182. Meanwhile, 47.85% (911/1904) of the patients in this study were diagnosed with positive lymph nodes. The Nottingham prognostic index (NPI), which is constructed by the tumor size, lymph node stage and pathological grade and is more discriminating than these characteristics alone [43], ranges from 1 − 6.360, with a median value of 4.033. The ER/PR status determines the hormone receptor status, which is important for deciding treatment options. In this dataset, the ER status of the patients determined by two different methods are similar: 1459 (76.63%) by ER expression and 1445 (77.11%) by ER immunohistochemistry (IHC) were identified as ER-positive. Additionally, 1009 (52.99%) of the patients were identified as PR-positive.
VDR and HER2 show large co-effects on clinical prognosis characteristics
To infer the prognostic roles of VDR in correlation with HER2 in BC, we performed multivariate analysis between VDR expression/CNA and clinical prognosis characteristics, which are grouped with their relationship to HER2 status as listed in Table 1 and S1 (see Materials and Methods [44–46]). We also performed the same analysis between HER2 expression/CNA and the same characteristics as a control. Consequently, we detected a great association between HER2 expression or CNA and clinical characteristics of HER2 status, HER2 SNP6, Claudin subtype and three-gene (ANOVA test, all P < 0.01, Table 2). Simultaneously, VDR expression and CNA also show significant effects on clinical characteristics related to HER2 status as demonstrated by HER2 analysis (ANOVA tests, all P < 0.01, Table 2), except HER2 SNP6. For characteristics unrelated to HER2 status, expression and CNA of both VDR and HER2 show significant effects on ages and ER status (ANOVA tests, all P < 0.05, Table 3). These results imply that VDR and HER2 exert co-effects on BC. However, substantial differences still exist, that tumor grade, cellularity, and IntClust are significantly associated with VDR expression and tumor stage with VDR CNA; cellularity is significantly associated with HER2 expression and tumor size with HER2 CNA. To some extent, those differences provide evidence for the effect variation of VDR and HER2 on BC.
Table 2
Effects of VDR/HER2 expression or copy number alteration (CNA) on clinical prognosis characters.
Clinical prognosis Characters | VDR | | HER2 |
Expression | CNA | | Expression | CNA |
Related to HER2 status | HER2 status | 9.515 ** | 17.272 *** | | 3828.117 *** | 2271.091 *** |
| HER2 SNP6 | 1.368 | 1.342 | | 90.463 *** | 245.672 *** |
| Claudin subtype | 5.399 *** | 6.297 *** | | 41.653 *** | 3.034 ** |
| Three-gene | 4.117 ** | 4.130 ** | | 13.344 *** | 5.773 *** |
Unrelated to HER2 status | Age at diagnosis | 4.423 * | 7.817 ** | | 41.615 *** | 20.817 *** |
| Grade | 4.845 * | 0.018 | | 0.898 | 0.865 |
| Tumor size | 0.705 | 1.143 | | 0.295 | 7.925 ** |
| Tumor stage | 2.416 | 3.978 * | | 0.585 | 0.043 |
| Lymph nodes examined positive | 0.065 | 1.039 | | 0.716 | 1.735 |
| NPI | 0.907 | 3.357 | | 0.460 | 2.578 |
| ER status | 3.924 * | 79.735 *** | | 44.590 *** | 16.981 *** |
| ER IHC | 2.497 | 1.114 | | 0.566 | 1.137 |
| PR status | 2.424 | 0.227 | | 30.125 *** | 23.036 *** |
| Cellularity | 5.414 ** | 1.734 | | 5.907 *** | 0.476 |
| Cohort | 0.133 | 0.006 | | 73.919 *** | 6.095 * |
| Inferred menopausal state | 1.024 | 0.220 | | 0.379 | 0.255 |
| IntClust | 2.799 ** | 1.804 | | 7.566 *** | 4.509 *** |
| Histological subtype | 0.845 | 1.371 | | 0.618 | 0.340 |
| Laterality | 0.669 | 0.830 | | 0.685 | 0.021 |
Note: ANOVA F-values of single factor are shown, but that of interactions between/across factors are not shown. * P < 0.05; ** P < 0.01; *** P < 0.001. |
Table 3
Therapies and overall survival (OS) statistics of breast cancer patients.
Therapies/OS (number) | Number/median | % |
Chemotherapy (1904) | | |
Yes | 396 | 20.80 |
No | 1508 | 79.20 |
Hormone therapy (1904) | | |
Yes | 1174 | 61.66 |
No | 730 | 38.34 |
Radiotherapy (1904) | | |
Yes | 1137 | 40.28 |
No | 767 | 59.72 |
Breast surgery (1882) | | |
Breast conserving | 755 | 40.12 |
Mastectomy | 1127 | 59.88 |
OS months (1904) | | |
Median OS months (range) | 115.62 (0 ~ 355.20) | |
OS status (1904) | | |
Living | 801 | 42.07 |
Deceased | 1103 | 57.93 |
Vital status (1903) | | |
Died of disease | 622 | 32.69 |
Died of other causes | 480 | 25.22 |
Living | 801 | 42.09 |
A significantly positive correlation between VDR and HER2 status in breast tumors.
To further illustrate the association between VDR and HER2 in BC, we compared the VDR expression levels between HER2 status characterized by different clinicopathological features (Table 2). We observed that VDR was highly expressed in HER2 + cancers than HER2-negative ones (Mann-Whitney U test, P < 0.001, Fig. 1A), higher in the HER2 + tumors characterized in the three-gene model (Mann-Whitney U test, P < 0.001, Fig. 1B), higher in HER2 amplification gain characterized by SNP6 (Mann-Whitney U test, P < 0.01, Fig. 1C), and higher in HER2-enriched cancer of the claudin subtype (Mann-Whitney U test, P < 0.001, Fig. 1D). These results suggest the positive association of VDR with HER2 in BC, which is verified by the correlation analysis between VDR and HER2 expression levels (Pearson’s correlation, r = 0.1686, P < 0.001, Fig. 1E).
VDR and HER2 also appear to have similar significant effects on other clinical characteristics that have been widely exploited for targeted therapies and as signatures for outcomes in BC [47], such as age at diagnosis and ER status (Table 2). Although not all studies showed a significant correlation between VDR expression and age [48–51] in BC, we found a slightly negative correlation (Pearson’s correlation r = -0.06848, P = 0.002791) (Figure S1A). Additionally, we observed a higher VDR expression in ER-negative than in ER-positive cancers (Mann − Whitney U test, P < 0.01, Figure S1B). Taken together, the positive correlations of VDR expression with clinical characteristics related to HER2 status, and the negative correlations unrelated to HER2 status, imply a coordinated function of VDR and HER2 in BC.
Genes negatively co-expressed with VDR and HER2 are enriched with pathways related to translations.
Next, we investigated the coordinated function of VDR and HER2 in BC. We identified genes that are positively or negatively correlated with HER2 or VDR expression using a linear regression model in the whole transcriptome (see Materials and Methods). In this dataset, we identified 5105 and 5540 genes positively and negatively correlated with HER2 expression level, respectively, and 3762 and 3599 genes positively and negatively correlated with VDR expression, respectively (Figure. 2A). A total of 58.9% (2217/3762) of genes were positively correlated with both HER2 and VDR expressions, and 66.6% (2397/3599) were negatively correlated (Figure. 2B). To illustrate the underlying mechanisms of VDR and HER2 coordination, we performed functional enrichment analysis on the overlapping genes using ReactomeFIViz in Cytoscape (v3.8.2) [52]. Surprisingly, the overlapping negatively related genes were found to be mainly enriched in pathways related to translation, such as “GTP hydrolysis and joining of the 60S ribosomal subunit,” “Eukaryotic Translation Termination,” “Eukaryotic Translation Initiation,” “Eukaryotic Translation Elongation,” “Selenocysteine synthesis,” “L13a-mediated translational silencing of Ceruloplasmin expression,” “Peptide chain elongation,” “Formation of a pool of free 40S subunits,” and “Cap-dependent Translation Initiation.” Pathways related to nonsense-mediated decay were also enriched, such as “Nonsense Mediated Decay (NMD) independent of the Exon Junction Complex (EJC)” and “Nonsense Mediated Decay (NMD) enhanced by the Exon Junction Complex (EJC).” Only three pathways were enriched in the overlapping positively related genes: “Asparagine N − linked glycosylation,” “ER to Golgi Anterograde Transport,” and “Transport to the Golgi and subsequent modification.” Our results uncover the underlying mechanism that VDR and HER2 function coordinately to mainly repress translation in BC.
Lower VDR CNA shows better survival in breast cancer.
The prognostic importance of VDR and HER2 can be measured by the survival analysis and Cox proportional hazards models. In the dataset used, 396, 1174, 1137, and 755 patients received chemotherapy, hormone therapy, radiotherapy, and breast-conserving surgery, respectively (Table 3). The median overall survival (OS months) was 115.62 months (range, 0–355.20, Table 2). Of the 1103 (57.93%) deceased patients, 622 died of BC (OS and Vital status, Table 2). Then, we applied the survival analysis of VDR/HER2 expression/CNA in BC, taking the aforementioned therapies into consideration (see Materials and Methods). As shown in Table 4, chemotherapy, hormone therapy, VDR CNA, and HER2 expression were associated with a higher risk of death (positive coefficients and P < 0.05), but breast-conserving surgery was associated with a lower risk of death (negative coefficients and P < 0.05). Moreover, elevated HER2 expression and VDR CNA showed lower survival rates in BC. In contrast to the relative similarity of survival curves between high and low HER2 expression levels, VDR showed larger differences across different CNAs. Our results reveal that the combined effect of VDR CNA and HER2 expression may be a good target for BC therapies or drugs.
Table 4
Survival analysis based on VDR and HER2 in breast cancer.
Variables | coef | z | Pr(>|z|) |
Chemotherapy | 0.2152 | 2.596 | 0.009431 ** |
Hormone therapy | 0.2456 | 3.752 | 0.0001760 *** |
Radiotherapy | -0.007386 | -0.097 | 0.9229 |
Breast conserving | -0.8290 | -2.842 | 0.004485 ** |
Breast mastectomy | -0.3900 | -1.352 | 0.1763 |
VDR expression | -0.09806 | -1.010 | 0.3125 |
VDR CNA | 0.1650 | 2.066 | 0.03885 * |
HER2 expression | 0.07617 | 2.071 | 0.03836 * |
HER2 CNA | -0.006529 | -0.120 | 0.9045 |
Note: Cox Proportional Hazards regression were performed. * P < 0.05; ** P < 0.01; *** P < 0.001. |