Author's response to reviews

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1 Author's response to reviews Title: Rapid Induction of Orthotopic Hepatocellular Carcinoma in Immune-competent Rats by Ultrasound-guided Method and the Subsequent Low-dose Chemotherapy Authors: Hoi-Hung Chan Tian-Huei Chu Hsin-Fan Chien Cheuk-Kwan Sun Huay-Ben Pan Hsiao-Mei Kuo Tsung-Hui Hu Kwok-Hung Lai Jiin-Tsuey Cheng Ming-Hong Tai Version: 3 Date: 5 June 2010 Author's response to reviews: see over

2 Division of Gastroenterology, Department of Internal Medicine, Kaohsiung Veterans General Hospital 386, Ta-Chung 1st Road, Kaohsiung, 813 Taiwan, ROC Tel: ext 2075 Fax: June 3, 2010 Editor-in-Chief BMC Gastroenterology Dear Editor, Attached is a revised copy of the paper entitled Rapid Induction of Orthotopic Hepatocellular Carcinoma in Immune-competent Rats by Ultrasound-guided Method and the Subsequent Low-dose Chemotherapy by Hoi-Hung Chan, et al. We would like to submit this article for publication as an original article in your outstanding journal. The study reported in the paper found that ultrasound-guided tumor implantation of N1-S1 cells led to the growth of orthotopic HCC in about 60% of SD rats, which was comparable to the method of laparotomy. It is found to be a fairly effective and feasible method for establishing an animal model of HCC for future therapeutic trials. It greatly reduces the time period expecting for the tumor response to the experimental drugs. Moreover, we have shown the therapeutic efficacies of low-dose epirubicin chemotherapy on HCC growth in terms of tumor size, cancer cell proliferation, apoptosis as well as angiogenesis. But, the optimal dose of metronomic epirubicin should be substantiated by modifications of the present orthotopic animal model and running of clinical trials in the future. We hope that our findings can be helpful for clinical practice. All the listed Authors would like to express that 1) all the listed Authors have participated actively in the study; 2) all the Authors have read and approved the submitted manuscript; 3) the study complies with current ethical considerations; 4) the manuscript reports unpublished work

3 which is not currently under consideration elsewhere and will not be submitted to another journal until a final decision has been made; and 5) there are no conflicts of interest, unless those identified specifically by the Authors in the letter. A point-by-point response to the concerns A. To Dr. Francesco Bertolini (Referee 1), 1. The concept of metronomic chemotherapy is not from Hanahan. The two seminal papers in the field are from Browder/folkman (Cancer Res), and from the Kerbel lab (J Clin Invest). Thank you for providing the accurate information. We have made amendment in the text accordingly. 2. A treatment for only 7 days, albeit daily, can not be considered as metronomic. In fact, the concept of metronomic chemotherapy implies a long treatment with no breaks, and 7 days are a short period. Authors should a) discuss this issue or b) report the results of their preclinical findings as "7-day treatment" and not as metronomic or c) study the effect of this drug for a longer period of time. Thank you for giving the valuable comment! The name of the results of the preclinical findings has been changed to short-term (7-day), low-dose epirubicin chemotherapy instead of metronomic chemotherapy to reflect the actual condition of the experiment. 3. The preclinical efficacy of metronomic chemotherapy in HCC has been recently reported by the Kerbel lab (Tang et al, Neoplasia 2010;12:264-74). These data should be discussed and compared with results reported in the current manuscript. Thank you very much for providing an excellent reference! We would like to add the following paragraph into the manuscript. Tang et al., [38] recently reported an orthotopic advanced HCC model in which significant improved overall survival was observed using various combinations of metronomic chemotherapy regimens with targeted antiangiogenic drugs. This is quite impressive and encouraging. They used laparotomy method to create the orthotopic HCC in SCID mice and then monitored the changes in tumor sizes by using a novel non-invasive approach (transplantation of tumor cells that have been transfected with the β-hcg gene). Both that study and our present study have successfully established valuable orthotopic HCC models that can be followed noninvasively either using a gene tranfection method or sonographically. Our method has the additional advantage of being close to the clinical

4 situation in which ultrasound is the major tool for following tumor progression. Also, both studies have demonstrated the great potential of low-dose chemotherapy, either used alone or in combination with antiangiogenic agents, in the treatment of HCC. B. To Dr. Urban Emmenegger (Referee 2), Major Compulsory Revisions 1. Chan et al apply metronomic epirubicin therapy. However, there is a lack of rational given for the epirubicin dose chosen. By assuming a mean weight of 150 g per rat, the dose applied is 2 mg/kg/d, or 14 mg/kg given over 7 days (i.e., approximately 42 mg/sqm/week). This appears to be a relatively high dose of epirubicin, which is also reflected by the degree of hematological toxicity documented in Figure 4. Furthermore, one of the characteristics of metronomic chemotherapy is the long-term administration of such treatment, which is clearly not the case in the experiments by Chan et al. Admittedly, the definition of metronomic chemotherapy remains vague. In compliance with the Reviewer s comment, the term metronomic chemotherapy has been changed to short-term (7-day), low-dose epirubicin regimen, 0.3mg/day/rat x 7 days (total dose of 2.1mg) to reflect the actual condition of the experiment, while the risk of congestive heart failure might be significant only when achieving cumulative doses greater than 900 mg m -2, about 20mg kg -1 (Ref. Bertazzoli C et al, and Launchbury AP et al.). 2. Perpendicular tumor size measurements are commonly used to calculate tumor volumes. Did the authors attempt such calculations by using the caliper/us/ct data? And if yes: were the findings consistent with the data shown in this manuscript using the mean of two perpendicular tumor diameters? Thank you for suggesting a very good alternative for comparing the tumor sizes. Yes, we did perform such calculations by using the caliper/us/ct data. Similar results were obtained in terms of tumor volumes (US vs. caliper: n=55, correlation coefficient= , ***P < ; US vs. CT: n=15, correlation coefficient= , ***P < ). These calculations have been added to our revised manuscript. 3. The authors apply functional (perfusion) CT scanning but do not show any perfusion data is there a special reason for this? Such data could confirm the microvessel density changes presented in Figure 6c. Thank you for your excellent idea! It is because no direct significant correlation was obtained between the perfusion data and microvessel density changes. This explanation has been added to the manuscript. Minor Essential Revisions 1. Methods: The origin of the hepatocytes clone 9 used in Fig 5a should be specified.

5 We apologize for the missing information! The origin of the hepatocytes clone 9 used in Fig 5a has been added in our revised manuscript. A normal rat hepatocyte cell line (clone-9) derived from normal Sprague Dawley rat liver was purchased from Bioresource Collection and Research Center (BCRC no , Hsin-Chu, Taiwan. 2. Methods: Under Immunohistochemistry Analysis Chan et al list an anti-pecam-1 and an anti-cd31 antibody, yet CD31 and PECAM-1 are two names for the same molecule. How many antibodies were used? The terminology used in the Method/Results/Figure Legend sections as well as the label of Figure 6c should be addressed to avert confusion. Sorry for the mistakes! Actually, anti-pecam-1 and anti-cd31 antibodies are the same and there was only one antibody. The terminology used in the Method/Results/Figure Legend sections as well as the label of Figure 6c has been corrected. 3. Figure 1a: An arrow depicting the needle track and outlining the liver border would be helpful. Corrections have been made, thanks! 4. Figure 1d: How many rats per group were used for this analysis? Sorry for the missing data! Number of rats (US vs. laparotomy: 55 vs. 39), P= These data have been added in our revised manuscript. 5. Figure 3a: According to the text rats were sacrificed on day 17, not day 19 as indicated in Figure 3a. Thank you for your keen observation! We have made the correction. Discretionary Revisions 1. The future reader may be interested in whether rats without macroscopic tumor growth 10 days after inoculation developed tumors at a later stage. Absolutely true! We had ever performed follow-up ultrasound examination 2 weeks later for at least 10 of the rats, which did not show macroscopic tumor growth 10 days after inoculation. However, none of them showed positive finding. 2. Abstract: Microvessel density may be a more appropriate term to describe the results presented in Figure 6c than angiogenesis index. According to your professional comment, the term has been changed in our revised manuscript. 3. Background: Although Hanahan et al coined the term metronomic, the concept of metronomic chemotherapy was described by others (Browder et al Cancer Res. 2000;60(7): ; Klement et al J Clin Invest. 2000;105(8):R15-24). Thank you for providing the valuable references! We have made the correction. Looking forward to hearing from you soon.

6 Best regards! Sincerely yours, Hoi-Hung Chan, MD