Lung cancer is the most common cause of cancer-related death in men and women worldwide, with an estimated 222, 520 new diagnoses and 157, 300 deaths in the United States in 2010 (30
). The most common symptoms are shortness of breath, coughing (including coughing up blood) and weight loss (31
). Several treatment options are available for lung cancer including radiation therapy, chemotherapy, surgery and targeted drug therapy. Some of the treatments, such as chemotherapy, weaken the immune system and make the body more prone to infection (32
). Ceftriaxone, an FDA-approved third-generation cephalosporin antibiotic, which was used primarily for treatment of pneumonia, herein is reported to exert antitumor activities. Our data clearly show a role of ceftriaxone as a chemotherapeutic agent for lung carcinoma and strongly suggest that Aurora B as a potential therapeutic ‘off’ target of this drug.
Aurora kinases, a collection of highly related serine/threonine kinases, are comprised of Aurora A, B and C and are key regulators of mitosis performing vital functions in chromosome alignment, segregation and cytokinesis (33
). As a member of Aurora kinase family, Aurora B is a chromosomal passenger protein critical for accurate chromosomal segregation, cytokinesis and regulation of the mitotic checkpoint (34
). According to the literature, Aurora kinases have been shown to play important roles in regulating cell division. Inhibition of Aurora B kinase resulted in cell-cycle arrest or even cell death (35
). Azzariti et al.
) reported that AZD1152, a specific Aurora B inhibitor, suppressed chromosome alignment and segregation in both colon and pancreatic cancer cell lines, resulting in increased chromosome number and cellular apoptosis. Recently, Lee et al.
found that reversine, a well-known Aurora B inhibitor, suppressed oral squamous cell growth by interfering with the progression of the cell cycle (37
). To determine whether ceftriaxone has a similar effect in A549 cells, different concentrations of ceftriaxone were used to treat A549 cells for 12h, and changes in cell-cycle distribution were examined. Consistent with the report by Lee et al.
, our data show that the percentage of G2/M cells slightly increased after treatment with high doses (500 µM) of ceftriaxone, which suggests that ceftriaxone induces G2/M arrest of A549 cells (Supplementary Figure 2)
, available at Carcinogenesis
Online). Previous studies showed that Aurora B directly phosphorylates histone H3 not only at Ser10 but also at Ser28, resulting in mitotic chromosome condensation (38
). However, accumulating evidence indicates that Aurora B is highly expressed in several malignancies. Progressive increases in the nuclear expression of Aurora B is observed in prostate cancers with increasing Gleason grades compared with normal prostate (39
). Inappropriate phosphorylation of histone H3 in the entire cell cycle enhances proliferation of liver cancer cells (40
), which suggested aberrant expression of Aurora B might be involved in hepatocarcinogenesis. Previous studies provided immunohistochemical evidence showing that Aurora B is overexpressed in lung cancer tissues compared with normal adjacent tissues (41
). Consistent with this report, our results also showed that Aurora B expression is higher in several lung cancer cell lines, including A549, Calu-3 and H520 cells, compared with MRC-5 normal lung cells (). Moreover, inhibiting Aurora B by ceftriaxone suppressed anchorage-independent growth of A549, H520 and H1650 cells (–D). These results suggest Aurora B might play a significant role in lung cancer cell growth.
Aurora B is only expressed during mitosis and most normal cells in the human body do not proliferate rapidly. Thus, a number of Aurora B inhibitors, including JNJ-7706621, Hesperadin and PHA-739358 (34
, were selected because they could have a broader therapeutic effect than non-specific cytotoxic agents. A number of Aurora B inhibitors have demonstrated antitumor activity and some, such as AZD 1152, have subsequently entered clinical trials. However, neutropenia was observed in a Phase I trial (44
), suggesting that this agent had antiproliferation toxicity on the bone marrow. Therefore, finding Aurora B inhibitors, which are highly effective in suppressing Aurora B activity with low toxicity, is urgent and beneficial. Here we found that ceftriaxone, an FDA-approved cephalosporin antibiotic, specifically bound with Aurora B (–D) and suppressed its activity ( and ) in vitro
and in cells. Moreover, knockdown Aurora B decreases the inhibitory effects of ceftriaxone in anchorage-dependent growth of JB6 P+ () and A549 () cells. Importantly, an in vivo
xenograft animal model showed that ceftriaxone suppressed A549 and H520 lung cancer tumor growth by inhibiting Aurora B activity (, Supplementary Figure 1
, available at Carcinogenesis
Online). These results suggest that Aurora B is a secondary or ‘off’ target protein of ceftriaxone, which suppresses lung carcinoma progression.
In conclusion, we showed that Aurora B is highly expressed in lung cancer cell lines. Moreover, we provided evidence showing that ceftriaxone effectively suppresses anchorage-independent cell growth of lung cancer cells and in vivo tumor growth of A549 cells by inhibiting Aurora B activity. Overall, our findings support the anticancer efficacy of ceftriaxone through its targeting of Aurora B for the treatment of lung carcinomas.