Original articleSulforaphane as an adjunctive to everolimus counteracts everolimus resistance in renal cancer cell lines
Graghical abstract
Introduction
Increased knowledge about the molecular mechanisms involved in renal cell carcinoma (RCC) pathogenesis has led to the development and approval of a new class of therapeutics called targeted drugs. These targeted drugs, particularly the tyrosine kinase inhibitors sunitinib and sorafenib and the mechanistic target of rapamycin (mTOR) inhibitors temsirolimus and everolimus, have considerably widened the therapeutic spectrum and significantly improved progression-free survival. Still, they are not curative. Rather, all these agents almost inevitably fail, largely due to acquired resistance. In view of this obstacle, natural compounds have come into the focus of interest as potential complementary adjunctives to support “traditional” tumor therapy. In fact, use of complementary medicine (CM) together with conventional treatment is common among tumor patients. Between 40% (Üstündağ and Demir Zencirci, 2015) and 80% (Huebner et al., 2014, Saghatchian et al., 2014) of cancer patients have indicated that they apply CM in addition to conventional therapy. The most common reasons given for use of CM are dissatisfaction with conventional treatment, reduction of chemotherapeutic side effects (Gillett et al., 2012, Citrin et al., 2012), and to actively contribute to tumor therapy (Smith et al., 2016).
Despite the widespread use of CM, knowledge about its therapeutic potential is limited and only sparse information is available dealing with whether CM possesses potential in combating resistance development under chronic drug exposure. Therefore, an in vitro RCC cell culture protocol was designed to evaluate whether combined use of the phytochemical, sulforaphane (SFN), derived from cruciferous vegetables such as broccoli (Brassica oleracea), and the mTOR inhibitor everolimus might be superior to an everolimus monotherapy with respect to tumor growth and proliferation. SFN was chosen, since it has been demonstrated to interfere with cellular pathways involved in growth, apoptosis and motility, and suppresses tumor proliferation and metastasis in vitro and in vivo. High SFN intake has also been linked to a reduced cancer risk in several epidemiologic studies (Herr and Büchler, 2010, Higdon et al., 2007). A clinical trial has provided evidence that SFN down-regulates the prostate-specific antigen (PSA) level in men with prostate cancer, decreasing biochemical recurrence after radical prostatectomy (Cipolla et al., 2015). The relevance of SFN in RCC treated with an mTOR-inhibitor based regimen has to date not been evaluated. The current work points to SFN as a potent phytopharmaceutical, which might be of particular help in managing RCC treatment failure caused by chronic everolimus treatment.
Section snippets
Cell culture
Kidney carcinoma Caki-1 and KTCTL-26 cells were purchased from LGC Promochem, Wesel, Germany (Fogh et al., 1977, Högemann et al., 1994). A498 cells were derived from Cell Lines Service (Heidelberg, Germany). Caki-1 and KTCTL-26 cells were chosen, since both lines are derived from a clear cell renal cell carcinoma, which is the most common renal carcinoma tumor type. Both lines are VHL positive, whereas VHL function is disrupted in A498 cells. Tumor cells were grown and subcultured in RPMI 1640
Short-term combined SFN and everolimus additively reduces RCC growth and proliferation
5 nM everolimus, applied short-term for 48 h, induced a significant reduction in the number of Caki-1, KTCTL-26, and A498 cells (Fig. 1). A significant growth blocking effect was also observed when 5 µM SFN was applied, although this was less pronounced than that induced by 5 nM everolimus. Combined SFN-everolimus did not block cell growth better than did the everolimus monotherapy. Since 5 nM everolimus evoked a maximum effect, which could not be surpassed by adding SFN, the everolimus dosage was
Discussion
Despite improvements in treating RCC, resistance toward established drug regimens limits therapeutic efficacy of anti-tumor protocols. The results presented here, as well as results from other investigations, show that the mTOR inhibitor, everolimus, creates feedback loops during chronic treatment, leading to drug non-responsiveness (Juengel et al., 2014, Tsaur et al., 2012). Molecular analysis during non-responsiveness points to an everolimus driven enhanced expression of cdk1 and 2, cyclin A
Conflict of interest
We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.
Acknowledgment
This work was supported by the "Adolf Messer Stiftung”, Bad Soden, Germany.
References (32)
- et al.
Epigallocatechin gallate and sulforaphane combination treatment induce apoptosis in paclitaxel-resistant ovarian cancer cells through hTERT and Bcl-2 down-regulation
Exp. Cell Res.
(2013) - et al.
Sulforaphane attenuates EGFR signaling in NSCLC cells
J. Biomed. Sci.
(2015) - et al.
Allyl-, butyl- and phenylethyl-isothiocyanate activate Nrf2 in cultured fibroblasts
Pharmacol. Res.
(2011) - et al.
Dietary constituents of broccoli and other cruciferous vegetables: implications for prevention and therapy of cancer
Cancer Treat. Rev.
(2010) - et al.
Cruciferous vegetables and human cancer risk: epidemiologic evidence and mechanistic basis
Pharmacol. Res.
(2007) - et al.
Cytogenetic and growth factor gene analysis of a renal carcinoma cell line
Cancer Genet. Cytogenet.
(1994) - et al.
Acetylation of histone H3 prevents resistance development caused by chronic mTOR inhibition in renal cell carcinoma cells
Cancer Lett
(2012) Control of DNA synthesis and mitosis by the Skp2-p27-Cdk1/2 axis
Mol. Cell
(2004)- et al.
Exploring frontiers: use of complementary and alternative medicine among patients with early-stage breast cancer
Breast
(2014) - et al.
The cdk1-cyclin B complex is involved in everolimus triggered resistance in the PC3 prostate cancer cell line
Cancer Lett
(2011)
A phase II study of sulforaphane-rich broccoli sprout extracts in men with recurrent prostate cancer
Invest. New Drugs
Sulforaphane bioavailability and chemopreventive activity in women scheduled for breast biopsy
Cancer Prev. Res.
Identification of p27/KIP1 expression level as a candidate biomarker of response to rapalogs therapy in human cancer
J. Mol. Med.
Effect of Sulforaphane in men with biochemical recurrence after radical prostatectomy
Cancer Prev. Res.
Beliefs and perceptions of women with newly diagnosed breast cancer who refused conventional treatment in favor of alternative therapies
Oncologist
Continuous exposure of pancreatic cancer cells to dietary bioactive agents does not induce drug resistance unlike chemotherapy
Cell Death Dis
Cited by (0)
- 1
Department of Urology and Pediatric Urology, University Medical Center Mainz, Mainz, Germany.