Sulfated galactans from red seaweed Gracilaria fisheri target epidermal growth factor receptor (EGFR) and inhibit cholangiocarcinoma cells (CCA) proliferation

Cholangiocarcinoma (CCA) is increasing in incidence worldwide and is resistant to chemotherapeutic agents, making treatment of CCA a major challenge. Previous studies reported that natural sulfated polysaccharides (SPs) disrupted growth factor receptor activation in cancer cells. The present study, therefore, aimed at investigating the anti-proliferation effect of sulfated galactans (SG) isolated from the red seaweed Gracilaria fisheri (G. fisheri) on CCA cell lines. Direct binding activity of SG to CCA cells, epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) were determined. The effect of SG on proliferation of CCA cells was investigated. Cell cycle analyses and expression of signaling molecules associated with proliferation were also determined. The results demonstrated that SG bound directly to EGFR. SG inhibited proliferation of various CCA cell lines by inhibiting EGFR and extracellular signal-regulated kinases (ERK) phosphorylation, and inhibited EGF-induced increased cell proliferation. Cell cycle analyses showed that SG induced cell cycle arrest at the G0/G1 phase, down-regulated cell cycle genes and proteins (cyclin-D, cyclin-E, Cdk-4, Cdk-2), and up-regulated the tumor suppressor protein P53 and the cyclin-dependent kinase inhibitor P21. Taken together, these data demonstrate that SG from G. fisheri inhibited proliferation of CCA cells, and its mechanism of inhibition is mediated, to some extent, by inhibitory effects on EGFR activation and EGFR/ERK signaling pathway. SG presents a potential EGFR targeted molecule, which may be further clinically developed in a combination therapy for CCA treatment

Mud crab susceptibility to disease from white spot syndrome virus is species-dependent

<p>Abstract</p> <p>Background</p> <p>Based on a report for one species (<it>Scylla serrata</it>), it is widely believed that mud crabs are relatively resistant to disease caused by white spot syndrome virus (WSSV). We tested this hypothesis by determining the degree of susceptibility in two species of mud crabs, <it>Scylla olivacea </it>and <it>Scylla paramamosain</it>, both of which were identified by mitochondrial 16 S ribosomal gene analysis. We compared single-dose and serial-dose WSSV challenges on <it>S. olivacea </it>and <it>S. paramamosain</it>.</p> <p>Findings</p> <p>In a preliminary test using <it>S. olivacea </it>alone, a dose of 1 × 10⁶WSSV copies/g gave 100% mortality within 7 days. In a subsequent test, 17 <it>S. olivacea </it>and 13 <it>S. paramamosain </it>were divided into test and control groups for challenge with WSSV at 5 incremental, biweekly doses starting from 1 × 10⁴and ending at 5 × 10⁶copies/g. For 11 <it>S. olivacea </it>challenged, 3 specimens died at doses between 1 × 10⁵and 5 × 10⁵copies/g and none died for 2 weeks after the subsequent dose (1 × 10⁶copies/g) that was lethal within 7 days in the preliminary test. However, after the final challenge on day 56 (5 × 10⁶copies/g), the remaining 7 of 11 <it>S. olivacea </it>(63.64%) died within 2 weeks. There was no mortality in the buffer-injected control crabs. For 9 <it>S. paramamosain </it>challenged in the same way, 5 (55.56%) died after challenge doses between 1 × 10⁴and 5 × 10⁵copies/g, and none died for 2 weeks after the challenge dose of 1 × 10⁶copies/g. After the final challenge (5 × 10⁶copies/g) on day 56, no <it>S. paramamosain </it>died during 2 weeks after the challenge, and 2 of 9 WSSV-infected <it>S. paramamosain </it>(22.22%) remained alive together with the control crabs until the end of the test on day 106. Viral loads in these survivors were low when compared to those in the moribund crabs.</p> <p>Conclusions</p> <p><it>S. olivacea </it>and <it>S. paramamosain </it>show wide variation in response to challenge with WSSV. <it>S. olivacea </it>and <it>S. paramamosain </it>are susceptible to white spot disease, and <it>S. olivacea </it>is more susceptible than <it>S. paramamosain</it>. Based on our single-challenge and serial challenge results, and on previous published work showing that <it>S. serrata </it>is relatively unaffected by WSSV infection, we propose that susceptibility to white spot disease in the genus <it>Scylla </it>is species-dependent and may also be dose-history dependent. In practical terms for shrimp farmers, it means that <it>S. olivacea </it>and <it>S. paramamosain </it>may pose less threat as WSSV carriers than <it>S. serrata</it>. For crab farmers, our results suggest that rearing of <it>S. serrata </it>would be a better choice than <it>S. paramamosain </it>or <it>S. olivacea </it>in terms of avoiding losses from seasonal outbreaks of white spot disease.</p