Limits...
Autophagy induction by leptin contributes to suppression of apoptosis in cancer cells and xenograft model: involvement of p53/FoxO3A axis.

Nepal S, Kim MJ, Hong JT, Kim SH, Sohn DH, Lee SH, Song K, Choi DY, Lee ES, Park PH - Oncotarget (2015)

Bottom Line: Interestingly, inhibition of autophagic process by treatment with inhibitors and LC3B gene silencing blocked leptin-induced increase in cell number and suppression of apoptosis, indicating a crucial role of autophagy in leptin-induced tumor progression.Moreover, gene silencing of p53 or FoxO3A prevented leptin-induced LC3 II protein expression, suggesting an involvement of p53/FoxO3A axis in leptin-induced autophagy activation.Leptin administration also accelerated tumor growth in BALB/c nude mice, which was found to be autophagy dependent.

View Article: PubMed Central - PubMed

Affiliation: College of Pharmacy, Yeungnam University, Gyeongsangbuk-do, Republic of Korea.

ABSTRACT
Leptin, a hormone mainly produced from adipose tissue, has been shown to induce proliferation of cancer cells. However, the molecular mechanisms underlying leptin-induced tumor progression have not been clearly elucidated. In the present study, we investigated the role of autophagy in leptin-induced cancer cell proliferation using human hepatoma (HepG2) and breast cancer cells (MCF-7), and tumor growth in a xenograft model. Herein, we showed that leptin treatment caused autophagy induction as assessed by increase in expression of autophagy-related genes, including beclin-1, Atg5 and LC3 II, further induction of autophagosome formation and autophagic flux. Interestingly, inhibition of autophagic process by treatment with inhibitors and LC3B gene silencing blocked leptin-induced increase in cell number and suppression of apoptosis, indicating a crucial role of autophagy in leptin-induced tumor progression. Moreover, gene silencing of p53 or FoxO3A prevented leptin-induced LC3 II protein expression, suggesting an involvement of p53/FoxO3A axis in leptin-induced autophagy activation. Leptin administration also accelerated tumor growth in BALB/c nude mice, which was found to be autophagy dependent. Taken together, our results demonstrate that leptin-induced tumor growth is mediated by autophagy induction and autophagic process would be a promising target to regulate development of cancer caused by leptin production.

Show MeSH

Related in: MedlinePlus

Role of leptin-induced autophagy in tumor growth in xenograft modelHepG2 cells were injected subcutaneously into the rear flanks of 4 weeks old male BALB/c nude mice. After two weeks, animals were randomly divided into four groups; Control, Leptin (1 mg/kg), Leptin (1 mg/kg) combined with 3-MA (1 mg/kg) and 3-MA (1 mg/kg) alone. Leptin and 3-MA were given intraperitoneally every 36 h for 4 weeks. (A) Representative mice from each group at the end of the treatment. (B) Animals were sacrificed and tumor tissues were collected at the end of treatment. (C) (Tumor volume was measured twice weekly as described in materials and methods. D) Tumor tissues were isolated from each mouse after sacrifice and weight was measured. Values are expressed as mean ± SEM (n=5). *P<0.05 compared to control mice; #P< 0.05 compared to mice treated with leptin.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4466676&req=5

Figure 7: Role of leptin-induced autophagy in tumor growth in xenograft modelHepG2 cells were injected subcutaneously into the rear flanks of 4 weeks old male BALB/c nude mice. After two weeks, animals were randomly divided into four groups; Control, Leptin (1 mg/kg), Leptin (1 mg/kg) combined with 3-MA (1 mg/kg) and 3-MA (1 mg/kg) alone. Leptin and 3-MA were given intraperitoneally every 36 h for 4 weeks. (A) Representative mice from each group at the end of the treatment. (B) Animals were sacrificed and tumor tissues were collected at the end of treatment. (C) (Tumor volume was measured twice weekly as described in materials and methods. D) Tumor tissues were isolated from each mouse after sacrifice and weight was measured. Values are expressed as mean ± SEM (n=5). *P<0.05 compared to control mice; #P< 0.05 compared to mice treated with leptin.

Mentions: While autophagy induction correlates to the survival of cancer cells, the relationship if any between leptin-induced tumor growth and autophagy activation has not been explored. In this study, we hypothesized that leptin-induced tumor growth could be mediated by autophagy activation. For confirmation of the results observed from in vitro experiments, we prepared HepG2 tumor xenografts in BALB/c nude mice and confirmed these results in in vivo model. We first investigated the effect of leptin on tumor growth in. As shown in Fig. 7A and 7B, intraperitoneal injection with leptin promoted tumor growth in xenograft model consistent with the previous reports, also evidenced by increase in tumor volume (Fig. 7C) and tumor weight (Fig. 7D). Importantly, co-treatment with 3-MA, a pharmacological inhibitor of type III PI3K and finally inhibits autophagy, prevented leptin-induced tumor growth without significant effect by treatment with 3-MA alone, indicating a critical role of autophagic process in leptin-induced tumor growth. In xenograft model implanted with HepG2 cells, leptin treatment significantly increased expression of LC3II protein in tumor tissues, whereas 3-MA treatment inhibited leptin-induced LC3II protein expression (Fig. 7E, upper panel). Furthermore, suppression of Bax expression was almost completely recovered by co-administration with 3-MA (Fig. 7E, lower panel). These results further substantiate autophagy induction by leptin in vivo, and its role in tumor growth and suppression of apoptosis.


Autophagy induction by leptin contributes to suppression of apoptosis in cancer cells and xenograft model: involvement of p53/FoxO3A axis.

Nepal S, Kim MJ, Hong JT, Kim SH, Sohn DH, Lee SH, Song K, Choi DY, Lee ES, Park PH - Oncotarget (2015)

Role of leptin-induced autophagy in tumor growth in xenograft modelHepG2 cells were injected subcutaneously into the rear flanks of 4 weeks old male BALB/c nude mice. After two weeks, animals were randomly divided into four groups; Control, Leptin (1 mg/kg), Leptin (1 mg/kg) combined with 3-MA (1 mg/kg) and 3-MA (1 mg/kg) alone. Leptin and 3-MA were given intraperitoneally every 36 h for 4 weeks. (A) Representative mice from each group at the end of the treatment. (B) Animals were sacrificed and tumor tissues were collected at the end of treatment. (C) (Tumor volume was measured twice weekly as described in materials and methods. D) Tumor tissues were isolated from each mouse after sacrifice and weight was measured. Values are expressed as mean ± SEM (n=5). *P<0.05 compared to control mice; #P< 0.05 compared to mice treated with leptin.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4466676&req=5

Figure 7: Role of leptin-induced autophagy in tumor growth in xenograft modelHepG2 cells were injected subcutaneously into the rear flanks of 4 weeks old male BALB/c nude mice. After two weeks, animals were randomly divided into four groups; Control, Leptin (1 mg/kg), Leptin (1 mg/kg) combined with 3-MA (1 mg/kg) and 3-MA (1 mg/kg) alone. Leptin and 3-MA were given intraperitoneally every 36 h for 4 weeks. (A) Representative mice from each group at the end of the treatment. (B) Animals were sacrificed and tumor tissues were collected at the end of treatment. (C) (Tumor volume was measured twice weekly as described in materials and methods. D) Tumor tissues were isolated from each mouse after sacrifice and weight was measured. Values are expressed as mean ± SEM (n=5). *P<0.05 compared to control mice; #P< 0.05 compared to mice treated with leptin.
Mentions: While autophagy induction correlates to the survival of cancer cells, the relationship if any between leptin-induced tumor growth and autophagy activation has not been explored. In this study, we hypothesized that leptin-induced tumor growth could be mediated by autophagy activation. For confirmation of the results observed from in vitro experiments, we prepared HepG2 tumor xenografts in BALB/c nude mice and confirmed these results in in vivo model. We first investigated the effect of leptin on tumor growth in. As shown in Fig. 7A and 7B, intraperitoneal injection with leptin promoted tumor growth in xenograft model consistent with the previous reports, also evidenced by increase in tumor volume (Fig. 7C) and tumor weight (Fig. 7D). Importantly, co-treatment with 3-MA, a pharmacological inhibitor of type III PI3K and finally inhibits autophagy, prevented leptin-induced tumor growth without significant effect by treatment with 3-MA alone, indicating a critical role of autophagic process in leptin-induced tumor growth. In xenograft model implanted with HepG2 cells, leptin treatment significantly increased expression of LC3II protein in tumor tissues, whereas 3-MA treatment inhibited leptin-induced LC3II protein expression (Fig. 7E, upper panel). Furthermore, suppression of Bax expression was almost completely recovered by co-administration with 3-MA (Fig. 7E, lower panel). These results further substantiate autophagy induction by leptin in vivo, and its role in tumor growth and suppression of apoptosis.

Bottom Line: Interestingly, inhibition of autophagic process by treatment with inhibitors and LC3B gene silencing blocked leptin-induced increase in cell number and suppression of apoptosis, indicating a crucial role of autophagy in leptin-induced tumor progression.Moreover, gene silencing of p53 or FoxO3A prevented leptin-induced LC3 II protein expression, suggesting an involvement of p53/FoxO3A axis in leptin-induced autophagy activation.Leptin administration also accelerated tumor growth in BALB/c nude mice, which was found to be autophagy dependent.

View Article: PubMed Central - PubMed

Affiliation: College of Pharmacy, Yeungnam University, Gyeongsangbuk-do, Republic of Korea.

ABSTRACT
Leptin, a hormone mainly produced from adipose tissue, has been shown to induce proliferation of cancer cells. However, the molecular mechanisms underlying leptin-induced tumor progression have not been clearly elucidated. In the present study, we investigated the role of autophagy in leptin-induced cancer cell proliferation using human hepatoma (HepG2) and breast cancer cells (MCF-7), and tumor growth in a xenograft model. Herein, we showed that leptin treatment caused autophagy induction as assessed by increase in expression of autophagy-related genes, including beclin-1, Atg5 and LC3 II, further induction of autophagosome formation and autophagic flux. Interestingly, inhibition of autophagic process by treatment with inhibitors and LC3B gene silencing blocked leptin-induced increase in cell number and suppression of apoptosis, indicating a crucial role of autophagy in leptin-induced tumor progression. Moreover, gene silencing of p53 or FoxO3A prevented leptin-induced LC3 II protein expression, suggesting an involvement of p53/FoxO3A axis in leptin-induced autophagy activation. Leptin administration also accelerated tumor growth in BALB/c nude mice, which was found to be autophagy dependent. Taken together, our results demonstrate that leptin-induced tumor growth is mediated by autophagy induction and autophagic process would be a promising target to regulate development of cancer caused by leptin production.

Show MeSH
Related in: MedlinePlus