High Expression of Complement Component C7 Indicates Poor Prognosis of Breast Cancer and Is Insensitive to Taxane-Anthracycline Chemotherapy

Abstract

Background: Breast cancer is the most commonly diagnosed cancer worldwide. However, the well-known biomarkers are not enough to meet the needs of precision medicine. Novel targets are desirable and highly valuable for improved patient survival. In this regard, we identified complement component C7 as one of the candidates based on data from the OCOMINE database.

Methods: C7 expression was examined by immunohistochemistry in 331 cases of invasive ductal carcinoma (IDC), 45 cases of ductal carcinoma in situ (DCIS), and 52 cases of non-neoplastic tissues adjacent to tumor. Then, C7 expression was further confirmed by Western blot analysis based on IDC specimens and non-neoplastic breast specimens. The relationship between the C7 expression and prognosis of breast cancer patients was analyzed in order to investigate the function of C7 in breast cancer patients. Meanwhile, we also analyzed the relationship between the C7 expression and prognosis of 149 patients treated with conventional TE (taxane and anthracycline)-based chemotherapy. Then, a cohort of patients (22 cases) treated with TE neoadjuvant chemotherapy was used to further confirm the relationship between the C7 expression and TE-based chemosensitivity.

Results: In our present study, we reported for the first time that C7 was an independent prognostic factor of breast cancer and C7 expression of IDC tissues was higher than non-neoplastic tissues adjacent to tumor and DCIS. In a cohort of 331 IDC patients, high expression of C7 indicated poor prognosis especially in the triple negative subtype and luminal B subtype. Furthermore, C7 was also a promoting factor for triple negative subtype patients to develop bone metastasis. Meanwhile, we provided the first evidence that patients with high C7 expression were insensitive to TE (taxane and anthracycline)-based chemotherapy by analyzing a cohort of 149 patients treated with TE-based chemotherapy and another cohort of 22 patients treated with TE neoadjuvant chemotherapy.

Conclusions: In summary, high expression of C7 may promote breast cancer development and might be insensitive to TE-based chemotherapy. Our present study laid a foundation to help clinicians improve the identification of patients for TE-based chemotherapy by C7 in the era of precision medicine.

Keywords: C7; TE chemotherapy; bone metastasis; breast cancer; prognosis.

Figure 1

Bioinformatic and clinical analysis identified that C7 was a tumor promoter in breast cancer. (A) Normalized C7 mRNA levels were analyzed based on the gene expression profiling data from the ONCOMINE database, including 53 invasive breast carcinoma cases and 6 normal breast samples. (B) OS curves of breast cancer patients with C7 mRNA expression in the Kaplan-Meier plotter database. (C) C7 expression was shown in non-neoplastic and neoplastic segments. Red rectangle represented tumors and black rectangle represented non-neoplastic tissues adjacent to tumor (magnification 100× and 400×). (D) Western blot analysis of C7 expression in breast tumor specimens (IDC, n = 13) and their corresponding non-neoplastic breast tissues adjacent to tumor (n = 13). β-actin was used as a loading control. (E) Immunohistochemical staining of C7 in clinical specimens of non-neoplastic breast tissues adjacent to tumor, ductal carcinoma in situ (DCIS), and invasive ductal carcinoma (IDC). (F) Overall survival (OS) and progression-free survival (PFS) curves of IDC patients (n = 319) (log-rank test).

Figure 2

High expression of C7 indicated a shorter survival in IDC patients, especially in the triple negative subtype and luminal B subtype. (A, B) OS and PFS curves of patients with triple negative subtype (n = 49). (C, D) OS and PFS curves of patients with the non-triple negative subtype (n = 270). (E, F) OS and PFS curves of patients with the HER2-overexpression subtype (n = 34). (G, H) OS and PFS curves of patients with the luminal A subtype (n=28). (I, J) OS and PFS curves of patients with the luminal B subtype (n=208). [(A–J): log-rank test]..

Figure 3

High expression of C7 promoted breast cancer metastasis, recurrence, or death, mainly in the triple negative subtype and luminal B subtype. (A) Representative immunohistochemical images of C7 expression in patients who developed metastasis, recurrence, or death within 5 years and patients who were disease-free over 5 years, respectively (magnification 200× and 400×). (B) Among 218 IDC patients, C7 expression score in patients who developed metastasis, recurrence, or death within 5 years was higher than those who were disease-free over 5 years (Mann-Whitney U test, P = 0.002). (C) Among 218 IDC patients, 88.7% (47/53) of patients who developed metastasis, recurrence, or death within 5 years exhibited a high C7 expression, while 50.9% (84/165) of patients who were disease-free over 5 years showed a high C7 expression (P < 0.001). (D, E) In the triple negative subtype, C7 expression score (D) and percentage of high C7 expression (E) in patients who developed metastasis, recurrence, or death within 5 years was higher than those who were disease-free over 5 years. (F, G) In the non-triple subtype, C7 expression score (F) and percentage of high C7 expression (G) in patients who developed metastasis, recurrence, or death within 5 years was higher than those who were disease-free over 5 years. (H, I) In the HER2-overexpression subtype, there was no difference in the C7 expression score (H) or percentage of high C7 expression (I) between patients who developed metastasis, recurrence, or death within 5 years and those who were disease-free over 5 years in the luminal B negative subtype, but not in the HER2-overexpression subtype. (J, K) In the luminal subtype, C7 expression score (J) and percentage of high C7 expression (K) in patients who developed metastasis, recurrence, or death within 5 years was higher than those who were disease-free over 5 years. [(B, D, F, H, J): χ² test; (C, E, G, I, K): Mann-Whitney U test].

Figure 4

High expression of C7 promoted triple negative subtype patients developing bone metastasis (BM). (A) Representative images of C7 expression in primary tumor specimens from breast cancer patients with BM and patients without BM, respectively (magnification 200× and 400×). (B) C7 expression score in IDC patients who developed BM was higher than those without BM (P = 0.027). (C) Percentage of high C7 expression in patients who developed BM was higher than those than those without BM (P=0.005). (D) IDC patients with high expression of C7 exhibited earlier occurrence of BM. The median interval time from the diagnosis of breast cancer (BC) to BM in patients with high C7 expression was shorter than the low C7 expression group (P = 0.026). (F) In the triple negative subtype, C7 expression in patients with BM was much higher than that in those without BM (P = 0.004). (G, H) In the non-triple negative subtype (F, G), HER2-overexpression subtype (F) and luminal B subtype (G), no statistical difference of C7 expression was found between patients with BM and those without BM. (I) In luminal subtype, C7 expression in patients with BM was much higher than that in those without BM (P = 0.004). [(B, D–I): Mann-Whitney U test, C: χ² test].

Figure 5

High C7 expression indicated a shorter survival in breast cancer patients treated with TE-based chemotherapy. (A, B) OS and PFS curves of IDC patients treated with TE-based chemotherapy (n = 149). (C, D) OS and PFS curves of IDC patients treated with non-TE-based chemotherapy (n = 170). [(A–D) log-rank test].

Figure 6

High C7 expression indicated a shorter survival in breast cancer patients treated with TE-based chemotherapy, especially in the luminal B subtype. (A, B) OS and PFS curves of triple negative subtype patients who received TE-based chemotherapy (n = 19). (C, D) OS and PFS curves of non-triple negative subtype patients who received TE-based chemotherapy (n = 130). (E, F) OS and PFS curves of the HER2-overexpression subtype patients who received TE-based chemotherapy (n = 20). (G, H) OS and PFS curves of luminal B subtype patients who received TE-based chemotherapy (n = 102). [(A–H): log-rank test].

Figure 7

High expression of C7 promoted breast cancer progression in patients treated with TE-based chemotherapy. (A) Among 102 patients treated with TE-based chemotherapy, representative images of C7 expression in patients who developed metastasis, recurrence, or death within 5 years and patients who were disease-free over 5 years, respectively (magnification 200× and 400×). (B) Among TE-based chemotherapy-treated patients, C7 expression in patients who developed metastasis, recurrence, or death within 5 years was higher than those who were disease-free over 5 years. (C) Among non-TE-based chemotherapy-treated cases, no significant difference of C7 expression was found in patients who developed metastasis, recurrence, or death within 5 years and those who were disease-free over 5 years. [(B, C): Mann-Whitney U test].

Figure 8

High expression of C7 promoted disease progression in luminal B subtype patients treated with TE-based chemotherapy. (A, B) Among patients treated with TE-based chemotherapy, the percentage of high C7 expression in patients who developed metastasis, recurrence, or death within 5 years was higher than those who were disease-free over 5 years in the non-triple negative subtype (B), but not in the triple negative subtype (A). (C, D) Among patients treated with TE-based chemotherapy, the percentage of high C7 expression in patients who developed metastasis, recurrence, or death within 5 years was higher than those who were disease-free over 5 years in the luminal B subtype (D), but not in the HER2 overexpression subtype (C). [(A–D): χ² test].

Figure 9

Patients with high C7 expression were insensitive to TE neoadjuvant chemotherapy. (A) Representative immunohistochemical images of C7 expression in both positive and negative pathological response groups, respectively (magnification 200× and 400×). (B) C7 expression in the negative pathological response group (n = 7) was higher than the positive pathological response group (n = 15, Mann-Whitney U test, P = 0.047).