Milciclib and Sorafenib Synergistically Downregulate C-Myc to Suppress
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Journal of Translational Science Research Article ISSN: 2059-268X Milciclib and sorafenib synergistically downregulate c-Myc to suppress tumor growth in an orthotopic murine model of human hepatocellular carcinoma Aastha Jindal1, Vaseem A Palejwala2, Marina Ciomei3, Anna Degrassi3, Gemma Texido3 and Kunwar Shailubhai1,2* 1Baruch S. Blumberg Institute, Pennsylvania Biotechnology Center, Doylestown, PA, USA 2Tiziana Lifesciences, 3805 Old Easton Road, Doylestown, PA, USA 3Nerviano Medical Sciences, 20014 Nerviano, Milan, Italy Abstract Complex heterogeneity in HCC pateints, due to multiple etiological factors, implies that monotherapy targeting a single mechanism might not be sufficient for sustained clinical response as another compensatory signaling could get activated to develop drug resistance. Thus, combination therapies utilizing drugs, preferentially with different mode of action, might be clinically more satisfactory. Milciclib (PHA-848125AC), a pan-inhibitor of cyclin dependent kinases (CDKs: CDK1, CDK2, CDK4, CDK5 and CDK7) and c-Src kinase, has shown anti-cancer activity in tumor models as well as in clinical studies with cancer patients, including HCC. Here, we present data demonstrating anti-HCC activity of milciclib in cell lines as well as in two different animal models HCC. Importantly, milciclib exhibited synergistic anti-HCC effect with sorafenib, a first-line tyrosine kinase inhibitor (TKI) drug for HCC. Oral treatment with milciclib inhibited HCC tumor growth in TG221 mice, a miR-221-induced transgenic HCC model. We also developed an orthotopic model, by implanting human HCC cells (MHCC97-H) in liver of nude mice, in which tumor growth can be monitored by measuring serum levels of human α-fetoprotein (hAFP) but not mouse AFP. While milciclib or sorafenib alone inhibited tumor growth, the combination of these two drugs produced remarkable synergistic anti-HCC activity. Mechanism related tumor tissue analyses indicated that while milciclib and sorafenib inhibited their respective signaling pathways, these drugs interacted with each other to downregulate c-Myc to exert their synergistic anti- HCC activity. Our results suggest that milciclib may complement with a TKI to improve clinical outcome in advanced HCC patients. Introduction and other cancers in humans leading to downregulation of CDK2 inhibitor protein p27KIP1 [14-16]. In triple negative breast cancer Hepatocellular carcinoma (HCC) is the most common primary xenograft mouse model, orally administed milciclib (40 mg/kg) malignancy of the liver and a leading cause of cancer-related resulted in inhibition of tumor growth and metastatic progression [16]. deaths worldwide [1,2]. Chronic liver inflammation resulting from In two separate phase II clinical trials in patients with thymoma and prolonged viral hepatitis, nonalcoholic fatty liver disease, nonalcoholic thymic carcinoma, oral treatment with milciclib met both primary steatohepatitis and other metabolic disorders such as excessive alcohol endpoint PFS-3 (progression free survival at 3 months) and secondary consumption and exposure to aflatoxins represent major etiological endpoint OS, respectively. Several patients received drug for over 5 factors for HCC [1-3]. These multitude of underlying mechanisms that years, suggesting that oral treatment with milciclib is well-tolerated, affect disease course and patient prognosis underscores the importance and it can be used for long-term duration as well [17]. of a broad-spectrum approach to target multiple mechanisms underlying HCC development and promotion [4]. Current therapies The CDKs, key regulators in the progression of cell cycle, are for HCC include specific tyrosine kinase inhibitors (TKIs) such as known to be overexpressed in a variety of cancer types [18], possibly sorafenib (Nexavar®), regorafenib (Stivarga®), lenvatinib (Lenvima®) due to dysregulation in the retinoblastoma protein (pRb) pathway and cabozantinib (Cabometyx®) [5-9]. In addition, immunotherapies [18]. The downstream targets in the pRb pathway are members of the with nivolumab (Opdivo®) and pembrolizumab (Keytruda®) both E2F transcription factor family that are critical regulator of cell cycle inhibiting programmed cell death receptor PD-1, have also been progression [19]. Thus, we conducted an exploratory phase I clinical approved as second line treatment for advanced HCC [10,11]. Although trial with milciclib + gemcitabine combination in 16 patients with solid these therapies have shown significant clinical benefits for HCC patients, malignancies [20], who underwent multiple prior chemotherapies but the clinical response rate is still low. Thus, there is an immediate need for drugs, preferentially with different mechanisms, which could be used in suitable combinations to complement existing therapies and *Correspondence to: Kunwar Shailubhai, PA Biotechnology Center, 3805 Old to improve clinical outcome without compromising safety. Easton Road, Doylestown, PA 18902, USA, E-mail: [email protected] Milciclib, a small molecule pan inhibitor of multiple CDKs (CDK1, Key words: hepatocellular carcinoma, tyrosine kinase inhibitors, sorafenib, cyclin CDK2, CDK4 and CDK5), c-src kinase and wee 1 & 2 kinases, has dependent kinases, milciclib and c-Myc shown efficacy in several tumor models [12,13]. Overexpression of Received: August 03, 2020; Accepted: August 11, 2020; Published: August 13, miR-221 has been reported to be associated with hepatocarcinogenesis 2020 J Transl Sci, 2020 doi: 10.15761/JTS.1000416 Volume 7: 1-10 Jindal A (2020) Milciclib and sorafenib synergistically downregulate c-Myc to suppress tumor growth in an orthotopic murine model of human hepatocellular carcinoma and were found to be refractory to all of the existing cancer drugs, humidified CO2 incubator. The next day, media was removed and fresh including gemcitabine. The combination treatment was well-tolerated, EMT inducing media containing vehicle or test articles were added. and produced clinical responses in approximately 36% of patients, Plates were incubated for 10 days with media changes every 3 days. suggesting that milciclib was able to overcome resistance towards On the 10th day, the number of cells migrated to the lower chamber gemcitabine [20]. Since the microenvironment of the liver is highly was determined using Bio-Rad (Hercules, CA) automatic cell counter. vascularized and rich in nutrition, we believe xenograft models, Values obtained were normalized to uninduced samples and expressed involving the implantation of human HCC cells on the back of nude as a percent cell migration. mice, might not be very accurate to predict the efficacy of HCC drugs Micro RNA 221 induced HCC mouse model (TG221): TG221 [21]. Hence, we sought to develop a robust orthotopic HCC murine mice were kindly provided by Prof. M. Negrini, Univeristy of Ferrara, model with human MHCC97-H cells, which are highly metastatic Italy. Experimentation with the transgenic TG221mice (B6D2F2 and also produce human α-fetoprotein (hAFP), a tentative biomarker background) was performed in accordance with the authorized facility for HCC in humans. An important attribute of this model is that the of Nerviano Medical Srl, Italy under the Italian Ministry of Health growth of MHCC97-H derived tumor can be monitored by measuring authorization number 192/2009-A, D.L.116-92. Transgenic male mice hAFP. There seems to be a good correlation between tumor growth and overexpressing miR-221 (10-12 days old) that were administered one hAFP levels, but not with mouse AFP. The effect of drug candidates can intraperitoneal (IP) injection (7.5 mg/kg) of diethylnitrosamine (DEN) also be monitored qualitatively by measuring levels of hAFP in serum resulted in measurable tumor development (100% tumor incidence) [22]. at about 20-30 wks of age. The MRI scanning was performed for In this study, we report data suggesting that oral treatment with pre-treatment for randomization and post treatment to assess tumor milciclib may have potential to be developed in combination with one growth. Milciclib was administered by oral gavage (40 mg/kg BID) of the TKI drugs to expand clinical response. for 10 days. Magnetic resonance imaging (MRI) was performed with a 7.0 T Bruker Pharmascan to follow tumor growth. For evaluation of Materials and methods therapeutic efficacy, % tumor growth [(tumor volume day X- tumor Chemical Inhibitors: Milciclib (PHA-848125AC, milciclib volume day 0) *100/tumor volume day 0] of 2 or 3 lesions per animal maleate) was synthesized at NerPharma, S.r.l. (Nerviano, Italy), were considered. sorafenib (Nexavar®), regorafenib (BAY 73-4506), and lenvatinib Orthotopic tumor induction in athymic nude mice: Experiments (E7080) were purchased from Adooq Bioscience (Irvine, CA). were performed in accordance with the guidelines approved by Cell cultures: Human HCC cell lines were purchased from the Institutional Animal Care and Use Committee of Washington American Type Culture collection (ATCC) and cultured in Dulbecco’s Biotechnology Inc (Baltimore, MD). Food and water were given ad Modified Eagle’s Medium (DMEM) (23). MHCC97H and MHCC97L libitum and mice were housed following animal handling procedures were cultured in DMEM/F12 supplemented with 10% FBS, 1% pen- as per the NIH guidelines and approved IACUC protocol. Each mouse was ear-tagged to monitor growth by measuring hAFP levels in serum. strep, and 1% glutamax under a humidified atmosphere of 5% CO2 at 37°C and harvested by trypsinization. Test agents were dissolved in chremophor/ethanol