Original ArticlesSuppression of ribosomal protein RPS6KB1 by Nexrutine increases sensitivity of prostate tumors to radiation
Introduction
Prostate cancer (PCa) patients generally receive a total dose of 70–80 Gy in fractions over a period of 8–9 weeks for locally advanced disease (clinical stage T2c) through external beam or internal brachytherapy [1]. Accordingly, standard of care for these patients is combination of radiation therapy (XRT) with androgen deprivation therapy (ADT). This combination regimen has been shown to significantly improve 10-year progression-free survival and cancer-specific survival compared to RT alone [2]. However, both ADT and XRT are associated with side effects that affect health related quality of life significantly [3,4]. For example, radiation side-effects such as radiation proctitis, rectal toxicity, erectile dysfunction, impotence, gastro-intestinal bleeding and urinary dysfunction affect quality of life of patients receiving XRT [5]. Similarly, ADT alone is associated with skeletal complications including bone loss and osteonecrosis [6]. Additionally, a substantial fraction of men undergoing ADT plus XRT experience disease recurrence. Furthermore, intrinsic or acquired tumor cell resistance to these treatments is an additional problem. For example, about 37% of patients with localized high-risk PCa relapse due to radioresistance [7]. Dose escalation and addition of ADT as adjuvants have had some therapeutic benefits but are limited due to the associated side effects that affect quality of life [8]. Enhancing radiosensitivity of the tumor could increase cure rates. Work from our lab has demonstrated the potential utility of Nexrutine (Nx), a commercially available Phellodendron amurense bark extract, in PCa [[9], [10], [11]]. Here, we tested the hypothesis that Nx in combination with radiation will increase the efficacy of radiation by inhibiting survival of PCa cells both in vitro and in vivo.
Section snippets
Cell culture studies
PC-3, LNCaP and 22Rv1 cells purchased from ATCC (Manassas, VA) were cultured in F12-K medium (PC-3) and RPMI medium (LNCaP and 22Rv1), supplemented with 10% FBS and 100 μg/ml penicillin-streptomycin. No authentication was done on these cell lines since they were purchased from ATCC. PC-3 AR cells obtained from Dr. Vadlamudi (Dept. of OB-BYN at UTHSC at San Antonio) were used as described before [12]. No authentication was done by the authors.
Radiation experiments
Logarithmically growing cells were pretreated with
Inhibitory effects of Nx and radiation on cell survival
We performed cell survival assays with androgen responsive LNCaP, androgen independent PC-3, AR expressing PC-3 AR cells and castration resistant 22Rv1 cells following increasing doses of ionizing radiation (IR) ranging from 0.5 Gy to 8 Gy. We observed a linear dose response to radiation with LNCaP cells being most sensitive followed by PC-3, 22Rv1 cells and PC-3 AR cells were the most radioresistant (Fig. S1A). In addition, we observed that doses of 4 Gy and above were toxic with more than 90%
Discussion
The risk of failing treatment and dying from prostate cancer is partially predicted by three well-recognized prognostic factors including serum levels of prostate-specific antigen (PSA), clinical stage, and tumor grade (Gleason score). Accordingly, patients are categorized into three broad groups of risk of failure such as low, intermediate, and high. With contemporary treatment, low, intermediate and high-risk patients have 10-year biochemical control rates of 92%, 87% and 63%, respectively [7
Conflicts of interests
Authors declare that they have no competing interests.
Funding
This work was supported in part by the funds from Veterans Affairs-Merit Award I01 BX 000766-01; CPRIT (RP150166); National Center for Complementary and Alternative Medicine 1R01 AT007448 (APK) National Cancer Institute R01 CA 149516 (RG) and CPRIT RTA (RP 170345, SH).
Acknowledgements
We acknowledge support provided by Cancer Therapy and Research Center at University of Texas Health San Antonio through the National Cancer Institute support grant #2P30 CA 054174-17 (APK and RG). We acknowledge support provided by the CTRC 40th Anniversary Distinguished Professor of Oncology Endowment to APK. The authors acknowledge the support provided by Flow Cytometry Core Facility and thank Dr. Divya Chakravarthy for assistance with the flow cytometry analysis. The authors also thank Dr.
References (32)
- et al.
Gastrointestinal toxicity following radiotherapy for prostate cancer: a ring of fire
Eur. Urol.
(2011) - et al.
Long-term side effects of androgen deprivation therapy in men with non-metastatic prostate cancer: a systematic literature review
Crit. Rev. Oncol.-Hematol.
(2006) - et al.
Prevalence of osteoporosis during long-term androgen deprivation therapy in patients with prostate cancer
Urology
(2007) - et al.(2006)
- et al.
Seminal plasma proteins in prostatic carcinoma: increased nuclear semenogelin I expression is a predictor of biochemical recurrence after radical prostatectomy
Hum. Pathol.
(2012) - et al.
Akt-dependent activation of mTORC1 complex involves phosphorylation of mTOR (mammalian target of rapamycin) by IkappaB kinase alpha (IKKalpha)
J. Biol. Chem.
(2014) - et al.
Phase 2 trial of single-agent everolimus in chemotherapy-naive patients with castration-resistant prostate cancer (SAKK 08/08)
Eur. Urol.
(2013) - et al.
Reciprocal feedback regulation of PI3K and androgen receptor signaling in PTEN-deficient prostate cancer
Canc. Cell
(2011) - D.H. Moon, J.A. Efstathiou, R.C. Chen, What Is the Best Way to Radiate the Prostate in 2016?, Urologic Oncology:...
- et al.
Effectiveness of androgen-deprivation therapy and radiotherapy for older men with locally advanced prostate cancer
J. Clin. Oncol.
(2015)
Excellent results from high dose rate brachytherapy and external beam for prostate cancer are not improved by androgen deprivation
Am. J. Clin. Oncol.
Improved survival in patients with locally advanced prostate cancer treated with radiotherapy and goserelin
N. Engl. J. Med.
Butanol fraction containing berberine or related compound from nexrutine inhibits NFkappaB signaling and induces apoptosis in prostate cancer cells
Prostate
Akt/cAMP-responsive element binding protein/cyclin D1 network: a novel target for prostate cancer inhibition in transgenic adenocarcinoma of mouse prostate model mediated by Nexrutine, a Phellodendron amurense bark extract
Clin. Canc. Res. Offic. J. Am. Assoc. Cancer Res.
Crosstalk between RON and androgen receptor signaling in the development of castration resistant prostate cancer
Oncotarget
Cited by (19)
PPM1H is down-regulated by ATF6 and dephosphorylates p-RPS6KB1 to inhibit progression of hepatocellular carcinoma
2023, Molecular Therapy Nucleic AcidsIdentification of new aptamer BC-3 targeting RPS7 from rapid screening for bladder carcinoma
2023, Genes and DiseasesCitation Excerpt :Abnormal expression of ribosomal proteins can induce the occurrence of diseases such as tumors.43 The knockout of highly expressed ribosomal protein S6K (RPS6KB1) in prostatic cancer (PCa) cells was found to increase PCa sensitivity to radiation, which indicated RPS6KB1 to be a new target for PCa drug-assisted radiotherapy.44 We revealed RPS7 as the cellular target of BC-3 via mass spectrometry analysis.
Nuclear S6K1 regulates cAMP-responsive element-dependent gene transcription through activation of mTOR signal pathway
2022, Biochemical and Biophysical Research CommunicationsCitation Excerpt :S6K1, activated by mTOR-dependent phosphorylation, is the best-characterized effector that mediates cell size regulation [2]. Interestingly, hyperphosphorylated S6K1 predicts poor prognosis and radiation resistance in non-small cell lung cancer, breast cancer, and prostate tumors [3–5]. Recently, mTOR/S6K1 pathway inhibitors have emerged as combinatory therapeutic strategies to enhance radiation sensitization.
Androgen deprivation-induced elevated nuclear SIRT1 promotes prostate tumor cell survival by reactivation of AR signaling
2021, Cancer LettersCitation Excerpt :Colonies were air-dried and images were captured using an Epson Expression 10000XL scanner [9,22]. Tissue microarray (TMA) consisting of prostate specimens from radical prostatectomy performed at the University of Rochester Medical Center was constructed upon appropriate approval from the institutional review board [22,25,26]. The mean age of these patients at the time of surgery was 60.1 years (range 42–78 years) and the mean follow-up after the surgery was 52.7 months (range 1–115 months).
Suppression of FAK by nexrutine inhibits gastric cancer progression
2020, Life SciencesCitation Excerpt :In China, nexrutine has been used as a nutrient supplement. In the past decade, researchers have demonstrated that nexrutine exhibited a tumor-suppressive role in many cancers, such as prostate cancer [9], pancreatic cancer [10,11], breast cancer [12], and skin cancer [13]. However, currently, the impact of nexrutine on the pathogenesis of gastric cancer has not been investigated.