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FBXW7-mutated colorectal cancer cells exhibit aberrant expression of phosphorylated-p53 at Serine-15.

Li N, Lorenzi F, Kalakouti E, Normatova M, Babaei-Jadidi R, Tomlinson I, Nateri AS - Oncotarget (2015)

Bottom Line: Although still largely unknown, the last defense mechanism against CRC at the molecular level could be through a synergistic effect of the two genes.Immunoblotting data further confirmed that reduction of phospho-p53(Ser15) may contribute to the decreased efficacy of therapy in FBXW7-mutated CRC cells.Phospho-p53(Ser15) regulation by FBXW7 E3-ligase activity could provide important clues for understanding FBXW7 behavior in tumour progression and grounds for its clinical applicability thereafter.

View Article: PubMed Central - PubMed

Affiliation: Cancer Genetics & Stem Cell Group, Cancer Biology Unit, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham NG7 2UH, UK.

ABSTRACT
FBXW7 mutations occur in a variety of human cancers including colorectal cancer (CRC). Elucidating its mechanism of action has become crucial for cancer therapy; however, it is also complicated by the fact that FBXW7 can influence many pathways due to its role as an E3-ubiquitin ligase in proteasome degradation. FBXW7 and TP53 are tumour suppressors intensively implicated in colorectal carcinogenesis. Deletion mutations in these two genes in animal models mark the progression from adenoma to carcinoma. Although still largely unknown, the last defense mechanism against CRC at the molecular level could be through a synergistic effect of the two genes. The underlying mechanism requires further investigation. In our laboratory, we have used a phospho-kinase profiler array to illustrate a potential molecular link between FBXW7 and p53 in CRC cells. In vitro and in vivo assessments demonstrated aberrant induction of phosphorylated p53 at Serine 15 [phospho-p53(Ser15)] in human FBXW7-deficient CRC cells as compared to their FBXW7-wild-type counterparts. FBXW7 loss in HCT116 cells promoted resistance to oxaliplatin. Immunoblotting data further confirmed that reduction of phospho-p53(Ser15) may contribute to the decreased efficacy of therapy in FBXW7-mutated CRC cells. The findings may suggest the applicability of phospho-p53(Ser15) as an indicative marker of FBXW7-mutations. Phospho-p53(Ser15) regulation by FBXW7 E3-ligase activity could provide important clues for understanding FBXW7 behavior in tumour progression and grounds for its clinical applicability thereafter.

No MeSH data available.


Related in: MedlinePlus

p53 levels remained unchanged in FBXW7-mutant human CRC-tissues(A-D) IHC for p53 in human CRC with (C, D) and without (A, B) FBXW7 mutations. Boxed line indicates magnified tissue area. Scale bars; 50 μm. (E) Western blotting analysis of p53 expression in HCT116 and DLD-1 cell lines expressing or lacking FBXW7. β-actin was blotted for loading control. All experiments were repeated for two times.
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Figure 6: p53 levels remained unchanged in FBXW7-mutant human CRC-tissues(A-D) IHC for p53 in human CRC with (C, D) and without (A, B) FBXW7 mutations. Boxed line indicates magnified tissue area. Scale bars; 50 μm. (E) Western blotting analysis of p53 expression in HCT116 and DLD-1 cell lines expressing or lacking FBXW7. β-actin was blotted for loading control. All experiments were repeated for two times.

Mentions: Even though TP53 mutations have been reported in over 50% of human tumours [33], it was not possible to profile the TP53 status by molecular methods in the CRC-tissues utilized in our previous studies (Ian Tomlinson, personal communication) [28, 29]. However, our data show heterogeneous pattern of p53-staining. There was more p53 staining at the invasion front of CRCs with a small increase (not statistically significant) in total levels of p53 (p = 0.072) among CRC tissues with FBXW7-mutation (Figure 6, 6A-6E & data not shown). Of interest was the fact that the only controlled variable for the wild-type CRC-tissues examined was the presence of intact FBXW7. Similarly, the only controlled variable for the FBXW7-mutated tissues was the presence of an FBXW7 mutation with other cancer mutations remaining unidentified. Regardless of the unknown nature of the non-FBXW7 mutations, the presence of an FBXW7-mutation alone was adequate to give a consistent pattern of phospho-p53(Ser15) induction (mean-range; 1.67–2.33). Statistical analysis confirmed that phopsho-p53(Ser15)-induction in FBXW7-mutant tissues was highly significant (p < 0.0005) (Figure 5B). Although only a limited number of samples was available, the results pointed towards the suitability of phospho-p53(Ser15) induction as an independent indicative marker of CRC with FBXW7-mutation.


FBXW7-mutated colorectal cancer cells exhibit aberrant expression of phosphorylated-p53 at Serine-15.

Li N, Lorenzi F, Kalakouti E, Normatova M, Babaei-Jadidi R, Tomlinson I, Nateri AS - Oncotarget (2015)

p53 levels remained unchanged in FBXW7-mutant human CRC-tissues(A-D) IHC for p53 in human CRC with (C, D) and without (A, B) FBXW7 mutations. Boxed line indicates magnified tissue area. Scale bars; 50 μm. (E) Western blotting analysis of p53 expression in HCT116 and DLD-1 cell lines expressing or lacking FBXW7. β-actin was blotted for loading control. All experiments were repeated for two times.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4496214&req=5

Figure 6: p53 levels remained unchanged in FBXW7-mutant human CRC-tissues(A-D) IHC for p53 in human CRC with (C, D) and without (A, B) FBXW7 mutations. Boxed line indicates magnified tissue area. Scale bars; 50 μm. (E) Western blotting analysis of p53 expression in HCT116 and DLD-1 cell lines expressing or lacking FBXW7. β-actin was blotted for loading control. All experiments were repeated for two times.
Mentions: Even though TP53 mutations have been reported in over 50% of human tumours [33], it was not possible to profile the TP53 status by molecular methods in the CRC-tissues utilized in our previous studies (Ian Tomlinson, personal communication) [28, 29]. However, our data show heterogeneous pattern of p53-staining. There was more p53 staining at the invasion front of CRCs with a small increase (not statistically significant) in total levels of p53 (p = 0.072) among CRC tissues with FBXW7-mutation (Figure 6, 6A-6E & data not shown). Of interest was the fact that the only controlled variable for the wild-type CRC-tissues examined was the presence of intact FBXW7. Similarly, the only controlled variable for the FBXW7-mutated tissues was the presence of an FBXW7 mutation with other cancer mutations remaining unidentified. Regardless of the unknown nature of the non-FBXW7 mutations, the presence of an FBXW7-mutation alone was adequate to give a consistent pattern of phospho-p53(Ser15) induction (mean-range; 1.67–2.33). Statistical analysis confirmed that phopsho-p53(Ser15)-induction in FBXW7-mutant tissues was highly significant (p < 0.0005) (Figure 5B). Although only a limited number of samples was available, the results pointed towards the suitability of phospho-p53(Ser15) induction as an independent indicative marker of CRC with FBXW7-mutation.

Bottom Line: Although still largely unknown, the last defense mechanism against CRC at the molecular level could be through a synergistic effect of the two genes.Immunoblotting data further confirmed that reduction of phospho-p53(Ser15) may contribute to the decreased efficacy of therapy in FBXW7-mutated CRC cells.Phospho-p53(Ser15) regulation by FBXW7 E3-ligase activity could provide important clues for understanding FBXW7 behavior in tumour progression and grounds for its clinical applicability thereafter.

View Article: PubMed Central - PubMed

Affiliation: Cancer Genetics & Stem Cell Group, Cancer Biology Unit, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham NG7 2UH, UK.

ABSTRACT
FBXW7 mutations occur in a variety of human cancers including colorectal cancer (CRC). Elucidating its mechanism of action has become crucial for cancer therapy; however, it is also complicated by the fact that FBXW7 can influence many pathways due to its role as an E3-ubiquitin ligase in proteasome degradation. FBXW7 and TP53 are tumour suppressors intensively implicated in colorectal carcinogenesis. Deletion mutations in these two genes in animal models mark the progression from adenoma to carcinoma. Although still largely unknown, the last defense mechanism against CRC at the molecular level could be through a synergistic effect of the two genes. The underlying mechanism requires further investigation. In our laboratory, we have used a phospho-kinase profiler array to illustrate a potential molecular link between FBXW7 and p53 in CRC cells. In vitro and in vivo assessments demonstrated aberrant induction of phosphorylated p53 at Serine 15 [phospho-p53(Ser15)] in human FBXW7-deficient CRC cells as compared to their FBXW7-wild-type counterparts. FBXW7 loss in HCT116 cells promoted resistance to oxaliplatin. Immunoblotting data further confirmed that reduction of phospho-p53(Ser15) may contribute to the decreased efficacy of therapy in FBXW7-mutated CRC cells. The findings may suggest the applicability of phospho-p53(Ser15) as an indicative marker of FBXW7-mutations. Phospho-p53(Ser15) regulation by FBXW7 E3-ligase activity could provide important clues for understanding FBXW7 behavior in tumour progression and grounds for its clinical applicability thereafter.

No MeSH data available.


Related in: MedlinePlus