DNC News

Milk thistle during chemotherapy

November 20, 2005

Subject: Milk thistle extracts may increase benefit of chemotherapy against cancer while decreasing side effects.

I frequently forget to tell patients about the benefits of milk thistle during chemotherapy. My only excuse is that it is hard to teach old dogs new tricks. While a student it was drilled into my head how useful milk thistle extracts were for the liver, protecting against damage from all sort of toxins. A local story of Amanita mushroom poisoning and miraculous rescue with milk thistle sealed the thought. Thus in my mind Milk thistle and its extracts have always been linked to liver toxicity, hepatitis and alcoholic cirrhosis. It has been hard for me to change and link it to cancer treatment despite the research that suggests that it can be of great benefit.

There have been several studies which indicate milk thistle should be used in the treatment of gynecological cancers at the same time as chemotherapy. As early as 1996 researchers reported a that combining milk thistle extracts with either cisplatin or Adriamycin (Doxorubicin) increased the drug's effectiveness against ovarian cancer cells. [i] A study published in 2002 combined milk thistle extracts with the chemotherapy drug cisplatin (CDDP) and tested the effect on ovarian cancer. Adding the milk thistle increased the lethal effect of the drug on the tumor cells by 90%. [ii] These results prompted a second more detailed study and the initiation of a human trial in ovarian cancer. [iii]

Here in Denver we have a group of researchers from the University Health Sciences Center who have contributed a number of interesting studies. One paper published in 2004 looked at milk thistle extracts and their effect in combination with various chemotherapy drugs on breast cancer cells. They too found a synergistic effect of the combination, the most pronounced benefit in combination with Adriamycin. [iv] The same researchers showed a similar benefit of adding milk thistle to the treatment of prostate cancer. [v] They also showed a similar benefit of using milk thistle in combination with Adriamycin in treating lung cancer. [vi] Epidermal Growth Factor Receptors (EGFR) and ways to inhibit them are the hot topics in cancer treatment these days, especially in lung cancer where a number of the new drugs attempt to do just that. Our Denver researchers have shown that at least part of the reason that milk thistle works is that it does just that, acts as an EGFR inhibitor. [vii]

At the same time milk thistle increases the toxic effect of chemotherapy drugs against cancer cells it appears to lessen the toxicity against healthy cells. A study published in September, 2005 found that combining milk thistle extracts with Cisplatin reduced damage to the kidneys that normally results from the drug. [viii]

Patients frequently tell me that their oncologists are nervous about the supplements they take during chemotherapy, afraid that they will interfere with the benefit of the drugs they are prescribing. These well meaning physicians often convince these patients to forego the use of nutritional supplements until the “medical” phase of their treatment is completed. I am saddened when I see this happen. Looking at the current science regarding the use of milk thistle in conjunction with chemotherapy, this idea is outdated. In effect these well intentioned doctors have lowered the therapeutic effect of the drugs they prescribe while increasing risk of side effects. Milk thistle is not unique. Similar effects have been demonstrated with a number of other nutritional supplements.

When faced with this conflict of views, the easiest way to resolve them is to ask for data. “Could you please give me references to the studies that suggest that these supplements are harmful?” Absence of studies obviously is no proof the supplements are safe, but the search often yields data such as those presented in this letter on milk thistle, demonstrating clear benefit.

It is possible to learn new things.

  References:

[i]

Eur J Cancer. 1996 May;32A(5):877-82

Antiproliferative effect of silybin on gynaecological malignancies: synergism with cisplatin and doxorubicin .Scambia G, De Vincenzo R, Ranelletti FO, Panici PB, Ferrandina G, D'Agostino G, Fattorossi A, Bombardelli E, Mancuso S.

Department of Gynaecology, Catholic University , Rome , Italy .

The aim of this study was to test the antiproliferative activity of silybin, a flavonoid, on human ovarian and breast cancer cell lines. Since flavonoids are thought to act through Type II oestrogen binding sites (Type II EBS), silybin binding to Type II EBS was also examined. Silybin, used in concentrations from 0.1 to 20 microM, exerted a dose-dependent growth inhibitory effect on OVCA 433, A2780 parental and drug-resistant ovarian cancer cells, and MCF-7 doxorubicin (DOX)-resistant breast cancer cells (IC50 = 4.8-24 microM). Both L and D diastereoisomers of silybin were effective in inhibiting A2780 WT cell growth (IC50 = 14 and 20 microM, respectively). Flow cytometry revealed that silybin decreased the percentage of cells in the S and G2-M phases of the cell cycle with a concomitant increase in cells in the G0-G1 phase. Silybin was able to compete with [3H]E2 for nuclear but not cytosolic Type II EBS. Its affinity parallels its efficacy in inhibiting cell proliferation. Furthermore, silybin (0.1 and 1 microM) potentiates the effect of cisplatin (CDDP) (0.1-1 micrograms/ml) in inhibiting A2780 WT and CDDP-resistant cell growth. Similar results were obtained on MCF-7 DOX-resistant cells when silybin (0.1 microM) was associated with doxorubicin (0.1-10 micrograms/ml). As assessed by the Berembaum isobole method, the effect of silybin-CDDP and silybin-DOX combinations results in a synergistic action. Using the 'stem cell assay' described by Hamburger and Salmon [Science 1977, 197, 461-463], we found that silybin exerted a dose-dependent inhibition of clonogenic efficiency of cells derived from three ovarian tumours (IC50 = 7.4, 4 and 6.4 microM, respectively). Since CDDP and DOX are the two most commonly used drugs for gynaecological tumours, the clinical application of silybin is currently under investigation in our institute.

PMID: 9081370 [PubMed - indexed for MEDLINE]

[ii] Life Sci . 2002 Feb 8;70(12):1447-59. Silybin and its bioavailable phospholipid complex (IdB 1016) potentiate in vitro and in vivo the activity of cisplatin .

Giacomelli S, Gallo D, Apollonio P, Ferlini C, Distefano M, Morazzoni P, Riva A, Bombardelli E, Mancuso S, Scambia G.

Department of Obstetrics and Gynaecology, Catholic University of the Sacred Heart, Rome , Italy .

In this study we investigated whether the flavonoid silybin and its bioavailable derivative IdB 1016 (silipide) could enhance the antitumour activity of cisplatin (CDDP), the most commonly used drug in the treatment of gynaecological malignancies. Silybin alone up to 10 (M was unable to produce a relevant in vitro growth inhibition of A2780 cells, whereas CDDP was effective, giving an IC50 value of 0.5+/-0.14 microM. When silybin was combined with CDDP, a dose-dependent and statistically significant (p<0.05) increase of the CDDP activity was noticed, yielding IC50 values of 0.35+/-0.07 and 0.263+/-0.004 microM at silybin concentrations of 1 and 10 microM, respectively. The same trend was observed for in vivo experiments. IdB 1016 alone (1350 mg/kg) did not significantly affect tumour growth, whereas CDDP at the Maximum Tolerated Dose (12 mg/kg) produced a tumour weight inhibition (TWI%) of 80% and a log10 cell kill (LCK) of 0.7. Administration of both drugs resulted in a potentiation of the antitumour activity and TWI% and LCK increased to 90% and 1, respectively. Interestingly, mice receiving the combination recovered earlier in terms of body weight loss as compared to CDDP-treated mice. CDDP at 6 mg/kg yielded TWI of 44% and LCK of 0. The concomitant administration of IdB 1016 (1800 mg/kg) enhanced CDDP anti-tumour activity, with 68% TWI and 0.6 LCK. Finally, an antiangiogenic effect of IdB 1016 in an in vivo experimental model was demonstrated. Median haemoglobin value for the Matrigel from the vehicle-treated controls was 2.43 versus a value of 0.321 for the IdB 1016-treated animals.

PMID: 11883719 [PubMed - indexed for MEDLINE]

[iii] Eur J Cancer. 2003 Nov;39(16):2403-10.

Antitumour activity of the silybin-phosphatidylcholine complex, IdB 1016, against human ovarian cancer.

Gallo D, Giacomelli S, Ferlini C, Raspaglio G, Apollonio P, Prislei S, Riva A, Morazzoni P, Bombardelli E, Scambia G.

Department of Obstetrics and Gynaecology, Catholic University of the Sacred Heart, Lgo A. Gemelli, 8-00168, Rome, Italy.

This study aimed to assess, in an in vivo experimental model, the growth inhibitory effects of IdB 1016 (Silipide, a complex of silybin/phosphatidylcholine) when used as a single agent against human ovarian cancer. We also wanted to investigate the mechanism of the antiangiogenic action by assessing Vascular Endothelial Growth Factor (VEGF) levels and by using macroarray technology to evaluate the regulation of a panel of genes involved in angiogenesis. We also aimed to establish the plasma and tumour bioavailability of silybin after repeated administration of IdB 1016. Female nude mice bearing human ovarian cancer xenografts (A2780) received 450 mg/kg/day IdB 1016 daily by oral gavage until the end of the study. At sacrifice, blood and tumour specimens were collected and subsequently processed for the determination of silybin levels, VEGF levels or a gene expression profile. IdB 1016 was significantly active in inhibiting ovarian tumour growth. Treatment with 450 mg/kg/day for a total of 20 administrations produced a tumour weight inhibition (TWI%) of 78% and a Log10 Cell Kill (LCK) of 1.1. Free silybin levels were found to be 7.0+/-5.3 microg/ml and 183.5+/-85.9 ng/g tissue (mean+/-standard deviation (S.D.)) in the plasma and tumour samples, respectively. No significant differences were found in the concentration of human VEGF in xenografts from control and IdB 1016-treated mice. The array analysis suggested the downregulation of the VEGR receptor 3 and the upregulation of angiopoietin-2 as potential mechanisms for the antiangiogenic activity. In conclusion, these findings suggest IdB 1016 is a good candidate, with a relevant clinical potential, for use in the management of recurrent ovarian cancer. A phase II, non-randomised clinical study is now ongoing in our Institute aimed at evaluating the efficacy of daily administrations of IdB 1016 in the serological recurrence of ovarian cancer.

PMID: 14556934 [PubMed - indexed for MEDLINE]

[iv]

Synergistic anti-cancer effects of silibinin with conventional cytotoxic agents doxorubicin, cisplatin and carboplatin against human breast carcinoma MCF-7 and MDA-MB468 cells.

Tyagi AK , Agarwal C , Chan DC , Agarwal R .

Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, 4200 East 9th Avenue , Denver , CO 80262 , USA .

Significant emphasis is being placed on combination chemotherapy of cancer using cytotoxic agents and naturally occurring chemopreventive agents, having different mechanisms of action with non-overlapping toxicity. In this regard, here we assessed whether a cancer preventive agent silibinin synergizes the therapeutic potential of doxorubicin (Dox), cisplatin or carboplatin, the chemotherapeutic drugs, in both estrogen-dependent and -independent human breast carcinoma, MCF-7 and MDA-MB468 cells, respectively. When tested alone, each of the four agents showed growth inhibition in both the cell lines in a dose- and a time-dependent manner. Based on their growth inhibitory effects, several combinations of silibinin (25-100 microM) with Dox (10-75 nM), cisplatin (0.2-2 microg/ml) or carboplatin (2-20 microg/ml) were next assessed for their synergistic, additive and/or antagonistic efficacy towards cell growth inhibition and apoptotic death. The strongest synergistic effects for cell growth inhibition [combination index (CI) 0.35 for MCF-7 and 0.45 for MDA-MB468 cells] were evident at a silibinin dose of 100 microM plus 25 nM Dox, in both the cell lines. Most of the CIs for other combinations of these three drugs with silibinin also suggested strong synergistic effects for cell growth inhibition in both MCF-7 and MDA-MB468 cells . In quantitative apoptosis studies, combination of silibinin with Dox resulted in much stronger apoptotic death compared to each agent alone in both cell lines. In case of silibinin combination with cisplatin, it showed no additional apoptotic effect in either cell line. Similarly, silibinin plus carboplatin combination showed stronger apoptotic effect only in MCF-7 cells . Together, these results suggest a possible synergism between silibinin and conventional cytotoxic agents for breast cancer treatment, and warrant further in vivo studies in pre-clinical breast cancer models.

[v]

 
Silibinin sensitizes human prostate carcinoma DU145 cells to cisplatin- and carboplatin-induced growth inhibition and apoptotic death.

Dhanalakshmi S , Agarwal P , Glode LM , Agarwal R .

Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver , CO 80262 , USA .

In several recent studies, we have shown that silibinin inhibits the growth of human prostate cancer cells (PCA) both in vitro and in vivo. Here, we investigated the effect of silibinin in combination with cisplatin and carboplatin on human PCA DU145 cell growth and apoptosis. Cisplatin alone at 2 microg/ml dose produced 48% cell growth inhibition, whereas a combination with 50-100 microM silibinin resulted in 63-80% (p<0.05-0.001) growth inhibition. Similarly, compared to 68% growth inhibition at 20 microg/ml carboplatin, addition of 50-100 microM doses of silibinin caused 80-90% inhibition (p<0.005-0.001). In the studies assessing the effect of these combinations on cell cycle progression, a combination of cisplatin or carboplatin with silibinin resulted in a stronger G2-M arrest, compared to these agents alone showing a moderate G2-M and G1 arrests in case of cisplatin and silibinin, and a complete S phase arrest with carboplatin, respectively. A stronger G2-M arrest by these combinations was accompanied by a substantial decrease in the levels of cdc2, cyclin B1 and cdc25C. Silibinin/platinum compound combinations were also effective in inducing apoptosis where cisplatin and carboplatin when combined with silibinin enhanced apoptosis from 8 to 15% and from 20 to 40%, respectively. Apoptosis induction was further confirmed by PARP and caspases 3, 9 and 7 whose cleaved levels were also enhanced by combination treatment. In addition, there was a significant increase in cytochrome c release in the cytosol following treatment of DU145 cells with these combinations. Together, these results show a substantial increase in the efficacy of platinum compounds on human PCA cells, when combined with silibinin, which provide a rationale for further investigations with these combinations. Copyright 2003 Wiley-Liss, Inc.

PMID: 12866029 [PubMed - indexed for MEDLINE]

[vi]

 
Oral silibinin inhibits lung tumor growth in athymic nude mice and forms a novel chemocombination with doxorubicin targeting nuclear factor kappaB-mediated inducible chemoresistance.

Singh RP , Mallikarjuna GU , Sharma G , Dhanalakshmi S , Tyagi AK , Chan DC , Agarwal C , Agarwal R .

Department of Pharmaceutical Sciences, School of Pharmacy , University of Colorado Health Sciences Center , Denver , Colorado 80262 , USA .

The acute and cumulative dose-related toxicity and drug resistance, mediated via nuclear factor kappaB (NFkappaB), of anthracycline anticancer drugs pose a major problem in cancer chemotherapy. Here, we report that oral silibinin (a flavanone) suppresses human non-small-cell lung carcinoma A549 xenograft growth (P = 0.003) and enhances the therapeutic response (P < 0.05) of doxorubicin in athymic BALB/c nu/nu mice together with a strong prevention of doxorubicin-caused adverse health effects. Immunohistochemical analyses of tumors showed that silibinin and doxorubicin decrease (P < 0.001) proliferation index and vasculature and increase (P < 0.001) apoptosis; these effects were further enhanced (P < 0.001) in combination treatment. Pharmacologic dose of silibinin (60 mumol/L) achieved in animal study was biologically effective (P < 0.01 to 0.001, growth inhibition and apoptosis) in vitro in A549 cell culture together with an increased efficacy (P < 0.05 to 0.001) in doxorubicin (25 nmol/L) combination. Furthermore, doxorubicin increased NFkappaB DNA binding activity as one of the possible mechanisms for chemoresistance in A549 cells, which was inhibited by silibinin in combination treatment. Consistent with this, silibinin inhibited doxorubicin-caused increased translocation of p65 and p50 from cytosol to nucleus. Silibinin also inhibited cyclooxygenase-2, an NFkappaB target, in doxorubicin combination. These findings suggest that silibinin inhibits in vivo lung tumor growth and reduces systemic toxicity of doxorubicin with an enhanced therapeutic efficacy most likely via an inhibition of doxorubicin-induced chemoresistance involving NFkappaB signaling.

[vii]

Comment in:

•  Cancer Biol Ther. 2003 Sep-Oct;2(5):532-3.

 
Epidermal growth factor receptor mediates silibinin-induced cytotoxicity in a rat glioma cell line.

Qi L , Singh RP , Lu Y , Agarwal R , Harrison GS , Franzusoff A , Glode LM .

Department of Medicine, University of Colorado Health Sciences Center ; Denver , Colorado USA .

Silibinin, derived from milk thistle extract, has been shown to inhibit growth factor receptor-mediated mitogenic and cell survival signaling, and to alter cell cycle regulators. Alteration in pathways regulating cell growth likely account for silibinin's inhibition of tumor growth. Since the epidermal growth factor receptor (EGFR) is a key regulator in cell signaling pathways, in the present study we directly tested the hypothesis that the EGFR plays a key role in mediating silibinin cytotoxicity to cancer cells. We generated a cell line, 9L-EGFR, which stably expressed human EGFR; the parental rat glioma cell line, 9L, does not contain endogenous EGFR message or protein. Our results show that expression of EGFR was both necessary and sufficient for conferring toxicity in response to silibinin in 9L-EGFR cells. Addition of silibinin was shown to inhibit EGFR activation by EGF in 9L-EGFR cells. These studies support the hypothesis that silibinin toxicity to cancer cells involves the EGFR signaling pathway. The findings presented here provide a rationale for understanding the growth inhibition effect of silibinin in cancer cells, and warrant further investigation into the effect of silibinin on specific pathways of cell signaling mediated by the EGF receptor.

PMID: 14614320 [PubMed - indexed for MEDLINE]

[viii]

   
Cisplatin nephrotoxicity and protection by milk thistle extract in rats.

Karimi G , Ramezani M , Tahoonian Z .

Department of Pharmacodynamy and Toxicology, School of Pharmacy , Mashhad University of Medical Sciences Mashhad , Iran . gho_karimi@yahoo.com

The protective effect of methanolic extract of milk thistle seeds and silymarin against cisplatin-induced renal toxicity in male rats after a single intraperitoneal injection of 3 mg kg cisplatin were studied. Over 5 days, cisplatin-treated rats showed tubular necrosis and elevation in blood urea nitrogen (BUN) and serum creatinine (Scr). Pretreatment of animals with silymarin (50 mg kg) or extract (0.6 g kg) 2 h before cisplatin prevented the tubular damage. Rats treated with silymarin or extract 2 h after cisplatin had BUN and Scr significantly lower than those receiving cisplatin, but mild to moderate necrosis was observed. These results suggested that milk thistle may protect against cisplatin-induced renal toxicity and might serve as a novel combination agent with cisplatin to limit renal injury.

PMID: 16136217 [PubMed