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Tumor-associated mutant p53 promotes cancer cell survival upon glutamine deprivation through p21 induction

View Article: PubMed Central - PubMed

ABSTRACT

Cancer cells depend on glutamine to sustain their increased proliferation and manage oxidative stress, yet glutamine is often depleted at tumor sites due to excessive cellular consumption and poor vascularization. We have previously reported that p53 protein, while a well-known tumor suppressor, can contribute to cancer cell survival and adaptation to low glutamine conditions. However, the TP53 gene is frequently mutated in tumors, and the role of mutant p53 (mutp53) in response to metabolic stress remains unclear. Here, we demonstrate that tumor-associated mutp53 promotes cancer cell survival upon glutamine deprivation both in vitro and in vivo. Interestingly, cancer cells expressing mutp53 proteins are more resistant to glutamine deprivation than cells with wild type p53 (wtp53). Depletion of endogenous mutp53 protein in human lymphoma cells leads to cell sensitivity to glutamine withdrawal, while expression of mutp53 in p53 cells results in resistance to glutamine deprivation. Furthermore, we found that mutp53 proteins hyper-transactivate p53 target gene CDKN1A upon glutamine deprivation, thus triggering cell cycle arrest and promoting cell survival. Together, our results reveal an unidentified mechanism by which mutp53 confers oncogenic functions by promoting cancer cell adaptation to metabolic stresses.

No MeSH data available.


Related in: MedlinePlus

Tumors expressing mutant p53 are more resistant to glutaminase inhibitor treatment in vivo(a,b) Athymic Nude mice at 7 weeks old were injected with HCT116 p53 −/− cells on the left flank. HCT116 p53 −/− cells expressing mutp53 R248Q were injected on the right flank. Once the tumor size reached an average of 60 mm3, the mice were treated with 15 mg/kg of L-DON every other day by i.p. injection. Tumor size was measured over time. Data represent the mean ± S.D. (n=5 or 6 tumors as indicated), ***P≤.001, Student’s t-test. (c) Tumors with L-DON or vehicle treatment were harvested at day 11. Western blot was performed using the indicated antibodies.
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Figure 7: Tumors expressing mutant p53 are more resistant to glutaminase inhibitor treatment in vivo(a,b) Athymic Nude mice at 7 weeks old were injected with HCT116 p53 −/− cells on the left flank. HCT116 p53 −/− cells expressing mutp53 R248Q were injected on the right flank. Once the tumor size reached an average of 60 mm3, the mice were treated with 15 mg/kg of L-DON every other day by i.p. injection. Tumor size was measured over time. Data represent the mean ± S.D. (n=5 or 6 tumors as indicated), ***P≤.001, Student’s t-test. (c) Tumors with L-DON or vehicle treatment were harvested at day 11. Western blot was performed using the indicated antibodies.

Mentions: To further investigate whether mutp53 can protect cancer cells from glutamine starvation in vivo, we established xenograft tumors using HCT116 p53−/− cells expressing either an empty vector or mutp53 R248Q. Once tumors were established, mice were treated with the glutaminase inhibitor L-DON, and tumor volume was measured over time (Figure 7a and 7b). As expected, inhibition of glutamine metabolism by L-DON dramatically suppressed tumor growth in mice with p53 tumors. In contrast, L-DON treatment had no significant effect on tumor growth in mice harboring tumors with mutp53 R248Q (Figure 7a and 7b). Consistent with our previous results, L-DON treatment induced apoptosis as indicated by cleaved-PARP in p53 tumors, but not in tumors expressing mutp53 (Figure 7c). Together, these results show that mutp53 may play a role in tumor resistance to glutamine deprivation in vivo.


Tumor-associated mutant p53 promotes cancer cell survival upon glutamine deprivation through p21 induction
Tumors expressing mutant p53 are more resistant to glutaminase inhibitor treatment in vivo(a,b) Athymic Nude mice at 7 weeks old were injected with HCT116 p53 −/− cells on the left flank. HCT116 p53 −/− cells expressing mutp53 R248Q were injected on the right flank. Once the tumor size reached an average of 60 mm3, the mice were treated with 15 mg/kg of L-DON every other day by i.p. injection. Tumor size was measured over time. Data represent the mean ± S.D. (n=5 or 6 tumors as indicated), ***P≤.001, Student’s t-test. (c) Tumors with L-DON or vehicle treatment were harvested at day 11. Western blot was performed using the indicated antibodies.
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Related In: Results  -  Collection

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Figure 7: Tumors expressing mutant p53 are more resistant to glutaminase inhibitor treatment in vivo(a,b) Athymic Nude mice at 7 weeks old were injected with HCT116 p53 −/− cells on the left flank. HCT116 p53 −/− cells expressing mutp53 R248Q were injected on the right flank. Once the tumor size reached an average of 60 mm3, the mice were treated with 15 mg/kg of L-DON every other day by i.p. injection. Tumor size was measured over time. Data represent the mean ± S.D. (n=5 or 6 tumors as indicated), ***P≤.001, Student’s t-test. (c) Tumors with L-DON or vehicle treatment were harvested at day 11. Western blot was performed using the indicated antibodies.
Mentions: To further investigate whether mutp53 can protect cancer cells from glutamine starvation in vivo, we established xenograft tumors using HCT116 p53−/− cells expressing either an empty vector or mutp53 R248Q. Once tumors were established, mice were treated with the glutaminase inhibitor L-DON, and tumor volume was measured over time (Figure 7a and 7b). As expected, inhibition of glutamine metabolism by L-DON dramatically suppressed tumor growth in mice with p53 tumors. In contrast, L-DON treatment had no significant effect on tumor growth in mice harboring tumors with mutp53 R248Q (Figure 7a and 7b). Consistent with our previous results, L-DON treatment induced apoptosis as indicated by cleaved-PARP in p53 tumors, but not in tumors expressing mutp53 (Figure 7c). Together, these results show that mutp53 may play a role in tumor resistance to glutamine deprivation in vivo.

View Article: PubMed Central - PubMed

ABSTRACT

Cancer cells depend on glutamine to sustain their increased proliferation and manage oxidative stress, yet glutamine is often depleted at tumor sites due to excessive cellular consumption and poor vascularization. We have previously reported that p53 protein, while a well-known tumor suppressor, can contribute to cancer cell survival and adaptation to low glutamine conditions. However, the TP53 gene is frequently mutated in tumors, and the role of mutant p53 (mutp53) in response to metabolic stress remains unclear. Here, we demonstrate that tumor-associated mutp53 promotes cancer cell survival upon glutamine deprivation both in vitro and in vivo. Interestingly, cancer cells expressing mutp53 proteins are more resistant to glutamine deprivation than cells with wild type p53 (wtp53). Depletion of endogenous mutp53 protein in human lymphoma cells leads to cell sensitivity to glutamine withdrawal, while expression of mutp53 in p53 cells results in resistance to glutamine deprivation. Furthermore, we found that mutp53 proteins hyper-transactivate p53 target gene CDKN1A upon glutamine deprivation, thus triggering cell cycle arrest and promoting cell survival. Together, our results reveal an unidentified mechanism by which mutp53 confers oncogenic functions by promoting cancer cell adaptation to metabolic stresses.

No MeSH data available.


Related in: MedlinePlus