Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine with beneficial effects in a broad number of tumors, including the primary liver cancers hepatocarcinoma (HCC) and cholangiocarcinoma (CCA). Among them, melatonin has shown to modulate different cancer-associated processes and enhance drug efficacy against HCC and CCA. Therefore, melatonin has a potential role in improving the current therapeutic landscape in these liver tumors.
Primary liver cancer constitutes the sixth most prevalent type of tumor and is the fourth common cause of cancer-related mortality worldwide [1]. A total of 841,080 new cases were diagnosed in 2018, with an estimated 781,631 deaths and an age-standardized mortality rate of 8.5/100,000. The most frequent types of primary liver cancer in adults are hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), constituting HCC the 70-85% of cases and CCA the 30-15%, depending on the country [2]. Liver cancer also appears in children and adolescents, accounting hepatoblastoma (HB) and HCC for 67-80% and 20-33% of cases, respectively [2][3].
Unfortunately, most of the liver cancer patients are diagnosed in advanced stages when surgical treatment is not available [4]. Moreover, the high mortality associated with liver cancer is related to its lack of sensitivity and development of resistances to a few treatments that lead to the chemotherapy failure. These drawbacks may be explained, at least in part, by the various phenotypes and histological characteristics of tumor liver cells and its microenvironment [5]. Furthermore, the high refractoriness of liver cancer to treatments has been associated with the interaction of very complex and diverse mechanisms of chemoresistance, which can act synergistically to protect tumor cells from the chemotherapy agents [3].
Melatonin (N-acetyl-5-methoxytryptamine), the main product of the pineal gland, is an indoleamine with antioxidant, chronobiotic and anti-inflammatory properties [6]. A reduction of melatonin levels or a depressed excretion of its main metabolite, 6-sulfatoxymelatonin, have been related to an increased cancer risk, suggesting an anticancer role of this indoleamine [7]. Collectively, the published data strongly support the oncostatic actions of melatonin on different types of tumors, including liver cancer [8][9][10].
The inhibitory role of melatonin in hepatic tumors involves a number of different molecular and cellular processes including reduction of cellular proliferation, cell cycle arrest, limiting angiogenesis and metastasis and promoting cell death [10][11][12][13][14][15][16][17]. Moreover, melatonin reportedly increases the sensitivity of liver cancer cells to currently-available treatments [4][18], and as other natural compounds such as quercetin, curcumin and resveratrol, melatonin properties could ameliorate chemotherapeutic toxicity [19][20][21].
Carcinogenetic processes often involve oxidative stress, and administration of antioxidant molecules may reduce the damage to cancerous hepatocytes [22][21][23]. Melatonin acts as an indirect antioxidant and as a direct free radical scavenger, and displays an important role as an immunomodulatory and chronobiotic agent in different tissues, including liver [6][14][24][25]. These effects have been observed in several studies carried out with both in vitro and in vivo models of HCC and CCA, where melatonin administration showed a markedly antioxidant activity by modulating expression and activity of antioxidant enzymes and oxidant agents [26][27][28]. However, under different conditions researches have reported an increase in oxidative stress derived from melatonin treatment in these liver tumors, which could be attributed to the employ of higher doses of this indoleamine [18][29]. Results found suggest that oxidative stress modulation by melatonin could be useful in the HCC and CAA treatment and prevention.
Since circadian clock plays a key role in liver physiology and chronodisruption is known to augment hepatocarcinogenesis [30], different experiments have been carried out to analyze the association between the antioxidant and chronobiotic effects of melatonin in HCC. During hepatocarcinogenesis it has been described the appearance of circadian rhythm perturbations that contribute to the establishment of liver tumors; however, melatonin has also found to be effective in restoring the normal rhythms not only as single treatment but also in combination with several drugs, such as oxaliplatin and α-ketoglutarate. This chronobiotic activity has been associated to the ability of melatonin to regulate the acrophase, mesor and amplitude parameters of lipid peroxidation and components of the antioxidant system, revealing an hepatoprotective action of melatonin derived from circadian rhythms modulation [31][32][33][34].
Carcinogenesis is a multistage process usually promoted by a disturbed and uncontrolled cell proliferation, with cell cycle dysregulation, associated with an increase in tumor cell viability. In these events, melatonin involvement has also been described since several studies reported cell cycle arrest after administration of this indoleamine in HCC alone or in combination with several drugs, such as sorafenib and (-)-epigallocatechin-3-gallate (EGCG). Nonetheless, cytostatic effects of melatonin have been identified in different stages of cell cycle, some studies observed an arrest in G0/G1 phase and another in G2/M phase, while induction of p53 and decrease of cyclin D1 expression are mostly found [10][35][36][37][38][39][40]. In this line, melatonin also acts through the melatonin receptors MT1, MT3 and retinoic acid-related orphan receptor alpha (RORα) to arrest cell cycle and inhibit cell proliferation by increasing receptors expression not only in HCC but also in CCA [11][12][41]. Another relevant molecules involved in cell cycle modulation, the brain and muscle arnt-like protein 1 (Bmal1) and the circadian locomotor output cycles protein kaput (Clock) proteins, have been also reported to be modulated by melatonin in HCC [14]. Altogether, these results highlight the potential of melatonin as a cytostatic agent in the treatment of liver tumors.
Apoptosis is a cellular mechanism of programmed cell death which is involved in numerous diseases, including cancer. Resistance to apoptosis is one of the main hallmarks of cancer and selective induction of this type of cell death in cancer cells has emerged as an interesting possibility for new antitumor treatments [42]. In liver, apoptotic signaling is transduced mainly via two molecular pathways: the extrinsic or death receptor-mediated pathway and the intrinsic or mitochondria-dependent pathway. Although the extrinsic pathway is induced by death ligands located in the cellular membrane and the intrinsic pathway is initiated as consequence of mitochondria dysfunction, both concur in a common finnal stage [42][43].
Melatonin effects on apoptosis modulation have been broadly studied in liver tumors. In both cellular and animal models, melatonin has demonstrated to be a powerful proapoptotic agent by inducing the extrinsic and the intrinsic pathway not only in HCC but also in CCA [10][14][44][45][29][46]. Moreover, several signaling pathways have been identified as mechanisms responsible for melatonin-derived apoptosis induction, such as promotion of endoplasmic reticulum (ER) stress, activation of NF-κB pathway and reduction of oxidative and nitrosative stress by melatonin [17][45][46][47][48]. Proapoptotic effects of melatonin have been also found when combined with other compounds, such as doxorubicin, cisplatin, sorafenib, regorafenib, 5-fluorouracil and EGCG, where coadministration with melatonin led to a higher induction of apoptosis and chemosensitivity [39][40][49][50][51][52][53][54][55][56].
The process of autophagy constitutes a bulk degradation system with a key role in the maintenance of cellular homeostasis in order to promote adaptation and cell survival. Nevertheless, when there is a excessive stimulation, programmed cell death is induced instead of survival in a number of different pathophysiological situations including tumorigenesis [57]. Therefore, in cancer cells autophagy can act as a double-edged sword removing malignant cells and damaged mitochondria at the early stages, but inducing survival under hypoxia and ischemia conditions in the later phases, which can be also associated with chemotherapy resistance and tumor progression [18].
As the dual role of autophagy, melatonin effects also depend on the cellular context, finding an autophagy induction in HCC when administered melatonin, which was diminishing the proapoptotic activity of the indoleamine, since disruption of autophagy promoted apoptosis [16][58]. Similarly, melatonin and cisplatin combined administration also induced an autophagy flux, improving antitumor effects of cisplatin [59]. However, coadministration of melatonin with sorafenib led to a reduction of the sorafenib-induced autophagy, promoting death of hepatocytes [60][61]. Furthermore, mitophagy, a selective degradation process of mitochondrias, is also modulated by melatonin. Results showed an increased mitophagy-associated apoptosis when combined with sorafenib under normoxic conditions, while after hypoxic induction melatonin and sorafenib treatment led to the inhibition of a cytoprotective mitophagy [4][18].
Angiogenesis—the process of new blood-vessel growth from the existing vasculature—plays a key role facilitating tumor growth and the metastatic process and has been widely related with progression, invasion and metastasis of liver tumors [62][63][64].
The proangiogenic vascular endothelial growth factor (VEGF) along with the main regulator of hypoxia response, HIF-1α, are two major proteins involved in angiogenesis promotion. Melatonin has shown to impaired angiogenic and invasive abilities of liver cancer cells through inhibition of both VEGF and HIF-1α, as well as other related molecules, including STAT-3, the CBP/p300 co-activator, the forkhead box A2 (FOXA2) transcription factor expression, matrix metalloproteinase 9 (MMP-9) [13][15][65][66][67]. Curiously, long non-coding RNAs (lncRNA) and microRNAs (miRNA) have also been involved in this melatonin-derived antiangiogenic activity, such as lncRNA carbamoyl-phosphate synthase 1 intronic transcript 1 (lncRNA-CPS1-IT1), lncRNA RAD51 antisense RNA 1 (lncRNA RAD51-AS1) and miRNA let7i-p [66][68][69]. Regarding to proangiogenic and angiostatic chemokines, melatonin effects have not fully cleared, since contradictory results where observed in two HCC cell lines susceptible and resistant to amphotericin B (AmB). These findings indicate that clinical application of melatonin in patients with HCC should consider the liver tumor characteristics for the optimization of indole concentrations [70].
As previously indicated, melatonin acts as both antioxidant and chronobiotic but also as an immunomodulatory agent [6][14][24][25]. Some clinical results from case reports have shown that melatonin combination with immunotherapy impaired HCC progression and development of new liver tumors [71]. Additionally, preclinical studies exhibited interesting results where melatonin administration led to an increased immune response in both HCC and CCA models [72][73], in some cases accompanied by an anti-inflammatory activity [73].
All of these findings reporting antitumor actions of melatonin in the HCC and CCA liver tumors are summarized in Table 1.
Table 1. Basic characteristics of experimental studies evaluating antitumor effects of melatonin against liver tumors.
First Author, Publication Year, [Reference] |
Country |
Liver Tumor |
Experimental Model (n, Sample Size per Group) |
Administration Strategy |
Treatment Regimen |
Process Alteration |
Dakshayani et al. 2005 [26] |
India |
HCC |
In vivo Adult male Wistar rats Intraperitoneal injection of DEN followed by subcutaneous CCl4 (n = 6) |
Intraperitoneal melatonin |
5 mg/kg 20 weeks |
Antioxidant and hepatoprotective activity |
Dakshayani et al. 2007 [31] |
India |
HCC |
In vivo Adult male Wistar rats Intraperitoneal injection of DEN followed by subcutaneous CCl4 (n = 6) |
Intraperitoneal melatonin |
5 mg/kg Thrice a week 20 weeks |
Chronobiotic effect Antioxidant effect |
Subramanian et al. 2007 [27] |
India |
HCC |
In vivo 3-months-old male Wistar rats Intraperitoneal injection of DEN followed by subcutaneous of CCl4 (n = 6) |
Intraperitoneal melatonin |
5 mg/kg Daily 20 weeks |
Tumor growth inhibition Antioxidant activity |
Martín-Renedo et al. 2008 [10] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
0.1–10 mM 4, 6, 8 and 10 days |
Proliferation inhibition Apoptosis induction Cell cycle arrest |
Subramanian et al. 2008 [32] |
India |
HCC |
In vivo 3-months-old male Wistar rats Intraperitoneal injection of DEN followed by subcutaneous injection of CCl4 (n = 6) |
Intraperitoneal melatonin |
5 mg/kg Daily 20 weeks |
Chronobiotic effect Antioxidant effect |
Carbajo-Pescador et al. 2009 [11] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
1–2.5 mM 2, 4 and 6 days |
Proliferation inhibition Cell cycle arrest |
Ozdemir et al. 2009 [35] |
Turkey |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
0.05–1 mM 72 h |
Cell cycle arrest |
Fan et al. 2010 [49] |
China |
HCC |
In vitro Human HepG2 and Bel-7402 cell lines |
Melatonin + Doxorubicin |
0.01–10 µM 48 h |
Proliferation inhibition Apoptosis induction |
Laothong et al. 2010 [28] |
Thailand |
CCA |
In vivo Male Syrian golden hamsters Oral inoculation of 50 metacercariae of Opisthorchis viverrini (n = 5) |
Oral melatonin |
5, 10, 20 mg/kg Daily 30 days |
Antioxidant and protective activity |
Lin and Chuang 2010 [70] |
Taiwan |
HCC |
In vitro Human HCC cell lines: HCC24/KMUH (resistant to AmB-induced oxidative stress) and HCC38/KMUH: (susceptible to AmB-induced oxidative stress) |
Melatonin |
1 and 100 µM 24 h |
Proliferation increase |
Melatonin + AmB |
1 and 100 µM 24 h |
Antiangiogenic effect |
||||
Carbajo-Pescador et al. 2011 [12] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
1–2.5 mM 12, 24 and 48 h |
Proliferation inhibition |
Han et al. 2011 [41] |
New York |
CCA |
In vivo 6-weeks-old male BALB/c nude mice Subcutaneous injection of Mz-ChA-1 cells (n = 4) |
Intraperitoneal melatonin |
4 mg/kg Thrice a week 43 days |
Proliferation inhibition |
Carbajo-Pescador et al. 2012 [44] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
50–2000 µM 1, 6, 24 and 48 h |
Apoptosis induction |
Cid et al. 2012 [36] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin + MF exposure |
0.01–1000 nM 4, 5 and 7 days |
Proliferation inhibition |
Liu et al. 2012 [58] |
China |
HCC |
In vitro Mouse hepatoma cell line H22 |
Melatonin |
100 µM 24 h |
Apoptosis induction |
Melatonin + Beclin-1 RNAi Melatonin + 3-MA |
100 µM 24 h |
Autophagy blockade Apoptosis induction |
||||
In vivo 8-weeks-old female BALB/c mice Subcutaneous injection of H22 cells (n = 10) |
Intraperitoneal melatonin |
10 or 20 mg/kg Daily 14 days |
Autophagy induction |
|||
Zha et al. 2012 [47] |
China |
HCC |
In vitro Human HCC HepG2 cell line Human hepatocyte HL-7702 cell line |
Melatonin + Tunicamycin |
10−7 µM 24 h |
Proliferation inhibition Apoptosis induction |
Carbajo-Pescador et al. 2013 [13] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
1 nM and 1 mM 2, 4, 6, 8, 12 and 24 h or 24 h |
Hypoxia-dependent angiogenesis |
Fan et al. 2013 [50] |
China |
HCC |
In vitro Human HepG2 and SMMC-7721 cell lines |
Melatonin + Doxorubicin |
1 mM 24 h |
Apoptosis induction |
Melatonin + Doxorubicin + Tunicamycin |
0.1–1000 µM 24 h |
Proliferation inhibition Apoptosis induction |
||||
Fan et al. 2013b [51] |
China |
HCC |
In vitro Human HepG2 and SMMC-7721 cell lines |
Melatonin |
0.001–1000 µM 24 and 48 h |
Proliferation inhibition Apoptosis induction |
Laothong et al. 2013 [45] |
Thailand |
CCA |
In vivo 4-to-6-weeks-old male Syrian golden hamsters Oral inoculation of 50 metacercariae of Opisthorchis viverrini and 12.5 ppm DEN (n = 15) |
Oral melatonin |
10 or 50 mg/kg Daily 120 days |
Apoptosis induction |
Tomov et al. 2013 [71] |
Bulgaria |
HCC |
Case report 67-years-old female |
Intermittent administration of IL-2, BCG and oral melatonin |
20 mg Daily |
Immunomodulation |
Bennukul et al. 2014 [59] |
Thailand |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
0.5–5 mM 24 and 48 h |
Autophagy induction |
Melatonin + Cisplatin |
||||||
Ordóñez et al. 2014 [15] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
1 mM 24 h |
Angiogenesis and invasion inhibition |
Melatonin + IL-1β |
||||||
Verma et al. 2014 [33] |
Malaysia |
HCC |
In vivo Adult male mice Intraperitoneal injection of DEN (n = 6) |
Intraperitoneal melatonin |
0.5 mg/kg Thrice a week 10 weeks |
Antioxidant activity Modulation of circadian rhythms |
Laothong et al. 2015 [29] |
Thailand |
CCA |
In vitro Human KKU-M055 and KKU-M214 cell lines |
Melatonin |
0.5, 1 and 2 mM 48 h |
Oxidative stress activity Apoptosis induction |
Moreira et al. 2015 [17] |
Brazil |
HCC |
In vivo Male Wistar rats Intraperitoneal injection of DEN and 2-AAF administration at week 4 (n = 12) |
Oral melatonin |
1 mg/kg Daily 45 and 90 days |
Apoptosis induction |
Ordóñez et al. 2015 [16] |
Spain |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
2 mM 0.5–48 h |
Apoptosis induction Autophagy induction |
Colombo et al. 2016 [65] |
Brazil |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
1–106 nM 24 h |
Proliferation inhibition |
1 mM 24 h |
Inhibition of hypoxia-derived invasion |
|||||
Prieto-Domínguez et al. 2016 [18] |
Spain |
HCC |
In vitro Human HepG2, HuH7 and Hep3B cell lines |
Melatonin |
0.1–2 mM |
Proliferation inhibition Pro-oxidant activity Mitophagy induction Apoptosis induction |
Melatonin + Sorafenib |
||||||
Bu et al. 2017 [48] |
China |
HCC |
In vitro Human HepG2 cell line |
Melatonin + Tunicamycin |
10−6 –1 mM |
Apoptosis induction and ER stress |
Cheng et al. 2017 [72] |
China |
HCC |
In vitro Human HepG2 and Bel-7402 cell lines |
Melatonin |
0.1 mM |
Immunomodulation |
In vivo 6-weeks-old female BALB/c nude mice Injected with Exo-con or Exo-MT (0.1 mM melatonin) |
Exo-MT |
100 µL Daily 10 days |
||||
Hao et al. 2017 [52] |
China |
HCC |
In vitro Human Bel-7402, SNU-449, HepG2 and Hep3B 2.1-7 cell line |
Melatonin |
1 mM 48 h |
Proliferation inhibition Inhibition of cell migration ability Apoptosis induction |
Melatonin + CDDP |
||||||
Lin et al. 2017 [53] |
China |
HCC |
In vitro Human HuH7 cell line |
Melatonin |
1–5 mM 48 h |
Proliferation inhibition Apoptosis induction |
Melatonin + Sorafenib |
||||||
Liu et al. 2017 [60] |
China |
HCC |
In vitro Human HepG2 and Bel-7402 cell lines |
Melatonin |
10 µM 48 h |
Apoptosis induction |
Melatonin + Sorafenib |
1–100 µM 48 h |
Proliferation inhibition |
||||
10 µM 48 h |
Apoptosis induction Autophagy blockage |
|||||
Long et al. 2017 [37] |
China |
HCC |
In vitro Human Bel-7402, SMMC-7721 HCC cell lines Human normal liver L02 cell line |
Melatonin |
0.2–2 mM 48–72 h |
Proliferation inhibition |
Melatonin + Sorafenib |
1 mM 48 h 2 weeks |
Proliferation inhibition Cell cycle arrest |
||||
In vivo 4-weeks-old female BALB/c nude mice Subcutaneous injection of SMMC-7721 cells (n = 4) |
Intraperitoneal melatonin |
25 mg/kg Daily 18 days |
Tumor growth inhibition |
|||
Intraperitoneal melatonin + sorafenib |
||||||
Prieto-Domínguez et al. 2017 [4] |
Spain |
HCC |
In vitro Human Hep3B cell line |
Melatonin |
1 or 2 mM 24 or 48 h |
Pro-oxidant activity Proliferation inhibition |
Melatonin + Sorafenib |
Proliferation inhibition Blockade of sorafenib-induced mitophagy |
|||||
Sánchez et al. 2017 [38] |
Spain |
HCC |
In vivo 6-weeks-old male ICR mice Intraperitoneal injection of DEN |
Intraperitoneal melatonin |
5 or 10 mg/kg Daily 10, 20, 30, 40 weeks |
Cell cycle arrest Modulation of sphingolipid metabolism |
Wang et al. 2017 [66] |
Taiwan |
HCC |
In vitro Human HepG2 and HuH7 cell lines |
Melatonin |
1 mM 12, 24, 36, 48, 60 and 72 h |
Proliferation inhibition |
1 mM 24, 48 and 72 h |
Suppression of cell migration ability |
|||||
1 mM 24 h |
EMT inhibition |
|||||
In vivo 6-to-8-weeks-old male BALB/c nude mice Subcutaneous injection of HuH7 cells (n = 10) |
Intraperitoneal melatonin |
40 mg/kg Five days per week |
Tumor growth inhibition EMT suppression |
|||
Wongsena et al. 2017 [73] |
Thailand |
CCA |
In vivo 6-to-8-weeks-old male Syrian golden hamsters Oral infection with 50 metacercariae of Opisthorchis viverrini and oral administration with DEN (n = 7) |
Oral melatonin |
50 mg/kg Daily 30 days |
Immunomodulation |
Chen et al. 2018 [68] |
Taiwan |
HCC |
In vitro Human HuH7 and HepG2 cell lines |
Melatonin |
1 mM 12, 24, 36, 48, 60 and 72 h |
Proliferation inhibition |
1 mM 24, 48 and 72 h |
Suppression of migration and invasion abilities |
|||||
Melatonin + Etoposide |
1 mM 12, 24, 36, 48, 60, and 72 h |
Proliferation inhibition Apoptosis induction |
||||
Melatonin + Camptothecin |
1 mM 24 h |
|||||
Chen et al. 2018 [68] |
Taiwan |
HCC |
In vivo 6-weeks-old male BALB/c nude mice Subcutaneous injection of HuH7 cells (n = 6) |
Intraperitoneal melatonin |
40 mg/kg Five days/week 25 days |
Tumor growth inhibition Apoptosis induction |
Intraperitoneal melatonin + etoposide |
||||||
Colombo et al. 2018 [46] |
Brazil |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
1 mM 24 h |
Increase of NF-κB protein expression |
Dauchy et al. 2018 [34] |
USA |
HCC |
In vivo Male Buffalo rats Implantation of Morris 7288CTC hepatomas (control: n = 6; experimental: n = 9) |
Endogenous melatonin |
Increase of endogenous melatonin levels |
Tumor growth inhibition |
Sánchez et al. 2018 [14] |
Spain |
HCC |
In vitro Human Hep3B cell line |
Melatonin |
0.5 or 1 mM 1 h |
Proliferation inhibition Apoptosis induction |
Melatonin + SR9009 |
Proliferation inhibition |
|||||
Melatonin + Bmal1 siRNA |
0.5 or 1 mM 24 h |
Proliferation inhibition Apoptosis induction |
||||
In vivo 6-weeks-old male ICR mice Intraperitoneal injection of DEN (n = 4–8) |
Intraperitoneal melatonin |
5 or 10 mg/kg Daily 10, 20, 30, 40 weeks |
Circadian clock modulation Cell cycle arrest Apoptosis induction |
|||
Wang et al. 2018 [69] |
Taiwan |
HCC |
In vitro Human HepG2 and HuH7 cell lines |
Melatonin |
1 and 2 mM 12, 24, 36, 48, 60 and 72 h |
Proliferation inhibition |
1 and 2 mM 24, 48 and 72 h |
Suppression of migration and invasion abilities |
|||||
Melatonin + let-7i-3p inhibitor |
1 and 2 mM 24 and 48 h |
Proliferation inhibition Migration and invasion suppression |
||||
In vivo 6–8-weeks-old male BALB/c nude mice Subcutaneous injection of HuH7 cells (n = 6) |
Intraperitoneal melatonin |
40 mg/kg 5 days per week 35 days |
Tumor growth inhibition |
|||
El-Magd et al. 2019 [74] |
Egypt |
HCC |
In vivo Adult female rats Intraperitoneal injection of DEN and oral administration of 2-AAF at week 2 (n = 10) |
Intraperitoneal melatonin |
20 mg/kg Twice a week 5 weeks |
Apoptosis induction Antioxidant activity Reduction of angiogenesis and metastasis |
Intraperitoneal melatonin + MSCs |
||||||
Intraperitoneal injection of MSCs preincubated with melatonin |
5 µM 24 h |
|||||
Mohamed et al. 2019 [75] |
Egypt |
HCC |
In vivo Adult female rats Intraperitoneal injection of DEN followed by oral administration of 2-AAF at week 2 (n = 10) |
Intraperitoneal melatonin |
20 mg/kg Twice a week 5 weeks |
Tumor growth inhibition Apoptosis induction |
Intraperitoneal injection of MSCs preincubated with melatonin 5 µM for 24 h |
||||||
Zhang et al. 2019 [39] |
China |
HCC |
In vitro Human HepG2 cell line |
Melatonin |
3 mM 48 h |
Suppression of migration |
1 mM 14 days |
Proliferation inhibition |
|||||
Melatonin + EGCG |
3 mM 48 h |
Suppression of migration |
||||
1 mM 14 days |
Proliferation inhibition |
|||||
Zhou et al. 2019 [61] |
China |
HCC |
In vitro Human HepG2, 7721 and HuH7 HCC cell lines Human liver L02 cell line |
Melatonin |
1–100 µM 48 h |
Apoptosis induction |
10 µM 48 h |
Autophagy inhibition |
|||||
Melatonin + Sorafenib |
1–100 µM 48 h |
Proliferation inhibition Apoptosis induction |
||||
10 µM 48 h |
Autophagy inhibition |
|||||
Ao et al. 2020 [54] |
China |
HCC |
In vitro Human HepG2 and HuH7 cell lines |
Melatonin |
2.5 mM 24 h |
Apoptosis induction |
Mi and Kuang 2020 [40] |
China |
HCC |
In vitro Human HepG2 and Hep3B cell lines |
Melatonin |
1 or 2 mM 24, 48, 72, 96 h |
Proliferation inhibition |
1 or 2 mM 48 h |
Cell cycle arrest |
|||||
Melatonin + Cisplatin |
1 or 2 mM 24 and 48 h |
Proliferation inhibition Apoptosis induction |
||||
Wang et al. 2020 [55] |
China |
HCC |
In vitro Human SMMC-7721, cell line |
Melatonin + Regorafenib |
50 µM 24 h |
Antioxidant activity Apoptosis induction |
2-AAF, 2-acetylaminofluorene; AmB, amphotericin B; BCG, Bacillus Calmette-Guerin; Bmal1, brain and muscle arnt-like protein 1; CCA, cholangiocarcinoma; CDDP, Cis-dichlorodiamineplatinum; DEN, diethylnitrosamine; EGCG, (–)-epigallocatechin-3-gallate; EMT, epithelial-to-mesenchymal transition; ER, endoplasmic reticulum; Exo-con, exosomes from HepG2 cells; Exo-MT, exosomes from melatonin-treated HepG2 cells; HCC, hepatocarcinoma; MF, magnetic field; IL-1β, interleukin 1 beta; IL-2, interleukin-2; MSCs, mesenchymal stem cells; NF-κB, nuclear factor-kappa B; RNAi, interference RNA; siRNA, small interference RNA.
Melatonin has shown to exert antitumor effects in liver tumors, not only in the prevention but also in the treatment of the main primary liver tumors, HCC and CCA, by modulating a wide number of cellular processes, even protecting cells from the hepatotoxicity of other drugs. Among melatonin’s effects, as showed in Figure 1, it improves the immune response, enhances apoptosis, and positively influences the cell cycle and circadian rhythms; it also impairs tumor angiogenesis, invasion and cell proliferation. Considering its different roles on autophagy, melatonin may modulate this process depending on cellular context, always aimed at hindering tumor progression. Finally, combination studies with different molecule types, antitumor drugs, flavonoids and chemotherapeutics, provide evidence of the potential effects of melatonin as a coadjuvant agent to improve current treatments. Overall, research findings support a role for melatonin as a promising drug in the treatment armamentarium of liver tumors.
Figure 1. Cellular processes and protein expression modulated by melatonin in liver tumors. CAT, catalase; CDK, cyclin-dependent kinase; cIAP, cellular inhibitor apoptotic proteins; COX-2, cyclooxygenase-2; ERCC1, DNA excision repair cross complementary 1 protein; ERK, extracellular signal-regulated kinase; FOXA2, forkhead box A2; FoxO3a, forkhead box protein O3; foxp3, forkhead box P3; GPx, glutathione peroxidase; GSH, reduced glutathione; GST, glutathione S-transferase; HIF-1α, hypoxia-inducible factor 1α; IL-1, interleukin-1; IL-1β, interleukin 1 beta; IL-6, interleukin-6; IL-10, interleukin-10; iNOS, inducible nitric oxide synthase; JNK, c-Jun N-terminal kinase 1; LC3, microtubule-associated protein 1 light chain 3; lncRNA, long non-coding RNA; MEK, MAPK/ERK kinase 1; MMP-9, matrix metalloproteinase 9; Mn-SOD, manganese superoxide dismutase; mTOR, mammalian target of rapamycin; NF-κB, nuclear factor-kappa B; Nrf2, nuclear erythroid 2-related factor 2; PARP, poly(ADP-ribose) polymerase; PCNA, proliferating cell nuclear antigen; PD-L1, programmed death ligand 1; PINK1, PTEN induced putative kinase 1; RAF-1, ras activated factor 1; ROS, reactive oxygen species; Sirt3, sirtuin 3; Snail, zinc finger protein SNAI1; SOD, superoxide dismutase; TBARS, thiobarbituric acid reactive substances; TGF-β, transforming growth factor β; Th17, IL-17-producing T helper; TIMP-1, tissue inhibitor of metalloproteinases 1; TNF-α, tumor necrosis factor alpha; VEGF, vascular endothelial growth factor; XIAP, cellular and X-linked inhibitor apoptotic proteins.
The entry is from 10.3390/antiox10010103