Lamin B2 promotes the progression of triple negative breast cancer via mediating cell proliferation and apoptosis

Abstract

Triple negative breast cancer (TNBC) is a more common type of breast cancer with high distant metastasis and poor prognosis. The potential role of lamins in cancer progression has been widely revealed. However, the function of lamin B2 (LMNB2) in TNBC progression is still unclear. The present study aimed to investigate the role of LMNB2 in TNBC. The cancer genome atlas (TCGA) database analysis and immunohistochemistry (IHC) were performed to examine LMNB2 expression levels. LMNB2 short hairpin RNA plasmid or lentivirus was used to deplete the expression of LMNB2 in human TNBC cell lines including MDA-MB-468 and MDA-MB-231. Alterations in cell proliferation and apoptosis in vitro and the nude mouse tumorigenicity assay in vivo were subsequently analyzed. The human TNBC tissues shown high expression of LMNB2 according to the bioinformation analysis and IHC assays. LMNB2 expression was correlated with the clinical pathological features of TNBC patients, including pTNM stage and lymph node metastasis. Through in vitro and in vivo assays, we confirmed LMNB2 depletion suppressed the proliferation and induced the apoptosis of TNBC cells, and inhibited tumor growth of TNBC cells in mice, with the decrease in Ki67 expression or the increase in caspase-3 expression. In conclusion, LMNB2 may promote TNBC progression and could serve as a potential therapeutic target for TNBC treatment.

Keywords: Apoptosis; Breast cancer; Lamin B2 (LMNB2); Proliferation; Target; Triple negative breast cancer (TNBC).

Figure 1. Bio-analysis revealed that LMNB2 was highly expressed in TNBC tissues and correlated with the prognosis of TNBC patients

(A) The TCGA database showed the expression levels of LMNB2 in tumor tissues and the corresponding normal tissues. (B and C) The TCGA database exhibited the correlation between LMNB2 and disease-free survival rates in TNBC patients from different case groups. *P<0.05.

Figure 2. LMNB2 was high expression in human TNBC tissues

(A) IHC assays were performed to detect LMNB2 expression in human TNBC tissues, and the representative photographs were shown (100× and 200× magnification, respectively). (B) The results of IHC assays exhibited the expression levels of LMNB2 in corresponding normal tissues (H&E stain, 100× and 200× magnifications, respectively).

Figure 3. LMNB2 expression was effectively reduced in both MDA-MB-468 and MDA-MB-231 cells after the transfection of its shRNA plasmids

(A) qPCR assays exhibited the effective decrease expression of LMNB2 after the transfection of its shRNA plasmids in MDA-MB-468 and MDA-MB-231 cells, respectively. (B) Immunoblot assays exhibited the obvious decrease of LMNB2 expression levels following the transfection of its shRNA in MDA-MB-468 and MDA-MB-231 cells. Results are presented as mean ± SD, * P<0.05.

Figure 4. LMNB2 promotes cell proliferation of TNBC in vitro

LMNB2 promotes cell proliferation of TNBC in vitro. (A) Colony formation assays were performed in MDA-MB-468 and MDA-MB-231 cells upon the transfection of control or LMNB2 shRNA plasmids, and the number of colonies was manually counted. (B) Immunoblot assays exhibited the expression levels of Ki67 in the transfection of control or LMNB2 shRNA plasmids in MDA-MB-468 and MDA-MB-231 cells. *P<0.05

Figure 5. LMNB2 depletion stimulated the apoptosis of TNBC cells in vitro

(A and B) Flow cytometry assays were performed in MDA-MB-468 and MDA-MB-231 cells transfected with control or LMNB2 shRNA plasmids, and the proportion of apoptosis cells was compared between control and LMNB2 depletion cells. (C) Immunoblot assays exhibited the expression levels of caspase-3 in MDA-MB-468 and MDA-MB-231 cells transfected with control or LMNB2 shRNA plasmids. Results are presented as mean ± SD, * P<0.05.

Figure 6. LMNB2 contributes to tumor growth of TNBC cells in mice

(A) MDA-MB-231 cells infected with control or LMNB2 shRNA lentivirus were subcutaneously implanted into nude mice. After 15 days, the tumors were isolated and photographed, and the tumor volumes were measured every 3 days. Tumor growth curves were calculated and compared between LMNB2 knockdown and control groups. IHC assays showed the expression levels of LMNB2 (B), Ki67 (C), and caspase-3 (D) in tumors of the control or LMNB2 depletion groups. Results are presented as mean ± SD, * P<0.05.