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HIPK2 deficiency causes chromosomal instability by cytokinesis failure and increases tumorigenicity.

Valente D, Bossi G, Moncada A, Tornincasa M, Indelicato S, Piscuoglio S, Karamitopoulou ED, Bartolazzi A, Pierantoni GM, Fusco A, Soddu S, Rinaldo C - Oncotarget (2015)

Bottom Line: In particular, HIPK2 is required to complete cytokinesis and impaired HIPK2 expression results in cytokinesis failure and tetraploidization.Importantly, we found a significant correlation among reduced HIPK2 expression, high grade of malignancy, and high nuclear size, a marker of increased ploidy.Overall, these results indicate that HIPK2 acts as a caretaker gene, whose inactivation increases tumorigenicity and causes CIN by cytokinesis failure.

View Article: PubMed Central - PubMed

Affiliation: Experimental Oncology Laboratory, Regina Elena National Cancer Institute, Rome, Italy.

ABSTRACT
HIPK2, a cell fate decision kinase inactivated in several human cancers, is thought to exert its oncosuppressing activity through its p53-dependent and -independent apoptotic function. However, a HIPK2 role in cell proliferation has also been described. In particular, HIPK2 is required to complete cytokinesis and impaired HIPK2 expression results in cytokinesis failure and tetraploidization. Since tetraploidy may yield to aneuploidy and chromosomal instability (CIN), we asked whether unscheduled tetraploidy caused by loss of HIPK2 might contribute to tumorigenicity. Here, we show that, compared to Hipk2+/+ mouse embryo fibroblasts (MEFs), hipk2- MEFs accumulate subtetraploid karyotypes and develop CIN. Accumulation of these defects inhibits proliferation and spontaneous immortalization of primary MEFs whereas increases tumorigenicity when MEFs are transformed by E1A and Harvey-Ras oncogenes. Upon mouse injection, E1A/Ras-transformed hipk2- MEFs generate tumors with genetic alterations resembling those of human cancers derived by initial tetraploidization events, such as pancreatic adenocarcinoma. Thus, we evaluated HIPK2 expression in different stages of pancreatic transformation. Importantly, we found a significant correlation among reduced HIPK2 expression, high grade of malignancy, and high nuclear size, a marker of increased ploidy. Overall, these results indicate that HIPK2 acts as a caretaker gene, whose inactivation increases tumorigenicity and causes CIN by cytokinesis failure.

No MeSH data available.


Related in: MedlinePlus

E1A/Ras MEFs tumorigenicityA, Anchorage-independent growth of indicated MEFs was analyzed. The number of colonies obtained by seeding 3 × 104 cells at p2 after stable transfection are presented as mean ± SD. (*P <0.05, Student t test). Representative bright-fields of 10 days colonies are shown, right; scale bar, 200 μm. B, Kaplan-Meier tumor free curve is reported for indicated cells concentration. n= mouse number. C, Representative HE staining of indicated tumors; scale bar, 60 μm. D, Morphometrical evaluation of HE-stained sections from three different Hipk2+/+ and −/− tumors was performed. Nuclear area size distribution is reported in box plot graph (*P<0.001, Kruskal-Wallis non-parametric test). E, Metaphase karyotype distribution of indicated tumor-derived cells is shown; at least 90 metaphases were analyzed for each tumor.
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Figure 3: E1A/Ras MEFs tumorigenicityA, Anchorage-independent growth of indicated MEFs was analyzed. The number of colonies obtained by seeding 3 × 104 cells at p2 after stable transfection are presented as mean ± SD. (*P <0.05, Student t test). Representative bright-fields of 10 days colonies are shown, right; scale bar, 200 μm. B, Kaplan-Meier tumor free curve is reported for indicated cells concentration. n= mouse number. C, Representative HE staining of indicated tumors; scale bar, 60 μm. D, Morphometrical evaluation of HE-stained sections from three different Hipk2+/+ and −/− tumors was performed. Nuclear area size distribution is reported in box plot graph (*P<0.001, Kruskal-Wallis non-parametric test). E, Metaphase karyotype distribution of indicated tumor-derived cells is shown; at least 90 metaphases were analyzed for each tumor.

Mentions: To further characterize the phenotype produced by hipk2 absence, we evaluated the tumorigenicity of E1A/Ras Hipk2+/+ and −/− MEFs in vitro and in vivo. First, we examined the anchorage-independent growth capability by soft agar colony formation assay. We observed that E1A/Ras Hipk2−/− MEFs formed more colonies than E1A/Ras Hipk2+/+ MEFs and that these colonies were characterized by larger dimensions (Figure 3A).


HIPK2 deficiency causes chromosomal instability by cytokinesis failure and increases tumorigenicity.

Valente D, Bossi G, Moncada A, Tornincasa M, Indelicato S, Piscuoglio S, Karamitopoulou ED, Bartolazzi A, Pierantoni GM, Fusco A, Soddu S, Rinaldo C - Oncotarget (2015)

E1A/Ras MEFs tumorigenicityA, Anchorage-independent growth of indicated MEFs was analyzed. The number of colonies obtained by seeding 3 × 104 cells at p2 after stable transfection are presented as mean ± SD. (*P <0.05, Student t test). Representative bright-fields of 10 days colonies are shown, right; scale bar, 200 μm. B, Kaplan-Meier tumor free curve is reported for indicated cells concentration. n= mouse number. C, Representative HE staining of indicated tumors; scale bar, 60 μm. D, Morphometrical evaluation of HE-stained sections from three different Hipk2+/+ and −/− tumors was performed. Nuclear area size distribution is reported in box plot graph (*P<0.001, Kruskal-Wallis non-parametric test). E, Metaphase karyotype distribution of indicated tumor-derived cells is shown; at least 90 metaphases were analyzed for each tumor.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496358&req=5

Figure 3: E1A/Ras MEFs tumorigenicityA, Anchorage-independent growth of indicated MEFs was analyzed. The number of colonies obtained by seeding 3 × 104 cells at p2 after stable transfection are presented as mean ± SD. (*P <0.05, Student t test). Representative bright-fields of 10 days colonies are shown, right; scale bar, 200 μm. B, Kaplan-Meier tumor free curve is reported for indicated cells concentration. n= mouse number. C, Representative HE staining of indicated tumors; scale bar, 60 μm. D, Morphometrical evaluation of HE-stained sections from three different Hipk2+/+ and −/− tumors was performed. Nuclear area size distribution is reported in box plot graph (*P<0.001, Kruskal-Wallis non-parametric test). E, Metaphase karyotype distribution of indicated tumor-derived cells is shown; at least 90 metaphases were analyzed for each tumor.
Mentions: To further characterize the phenotype produced by hipk2 absence, we evaluated the tumorigenicity of E1A/Ras Hipk2+/+ and −/− MEFs in vitro and in vivo. First, we examined the anchorage-independent growth capability by soft agar colony formation assay. We observed that E1A/Ras Hipk2−/− MEFs formed more colonies than E1A/Ras Hipk2+/+ MEFs and that these colonies were characterized by larger dimensions (Figure 3A).

Bottom Line: In particular, HIPK2 is required to complete cytokinesis and impaired HIPK2 expression results in cytokinesis failure and tetraploidization.Importantly, we found a significant correlation among reduced HIPK2 expression, high grade of malignancy, and high nuclear size, a marker of increased ploidy.Overall, these results indicate that HIPK2 acts as a caretaker gene, whose inactivation increases tumorigenicity and causes CIN by cytokinesis failure.

View Article: PubMed Central - PubMed

Affiliation: Experimental Oncology Laboratory, Regina Elena National Cancer Institute, Rome, Italy.

ABSTRACT
HIPK2, a cell fate decision kinase inactivated in several human cancers, is thought to exert its oncosuppressing activity through its p53-dependent and -independent apoptotic function. However, a HIPK2 role in cell proliferation has also been described. In particular, HIPK2 is required to complete cytokinesis and impaired HIPK2 expression results in cytokinesis failure and tetraploidization. Since tetraploidy may yield to aneuploidy and chromosomal instability (CIN), we asked whether unscheduled tetraploidy caused by loss of HIPK2 might contribute to tumorigenicity. Here, we show that, compared to Hipk2+/+ mouse embryo fibroblasts (MEFs), hipk2- MEFs accumulate subtetraploid karyotypes and develop CIN. Accumulation of these defects inhibits proliferation and spontaneous immortalization of primary MEFs whereas increases tumorigenicity when MEFs are transformed by E1A and Harvey-Ras oncogenes. Upon mouse injection, E1A/Ras-transformed hipk2- MEFs generate tumors with genetic alterations resembling those of human cancers derived by initial tetraploidization events, such as pancreatic adenocarcinoma. Thus, we evaluated HIPK2 expression in different stages of pancreatic transformation. Importantly, we found a significant correlation among reduced HIPK2 expression, high grade of malignancy, and high nuclear size, a marker of increased ploidy. Overall, these results indicate that HIPK2 acts as a caretaker gene, whose inactivation increases tumorigenicity and causes CIN by cytokinesis failure.

No MeSH data available.


Related in: MedlinePlus