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Oncogenic mutations of thyroid hormone receptor β.

Park JW, Zhao L, Willingham M, Cheng SY - Oncotarget (2015)

Bottom Line: Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence.Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis.Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.

ABSTRACT
The C-terminal frame-shift mutant of the thyroid hormone receptor TRβ1, PV, functions as an oncogene. An important question is whether the oncogenic activity of mutated TRβ1 is uniquely dependent on the PV mutated sequence. Using four C-terminal frame-shift mutants-PV, Mkar, Mdbs, and AM-we examined that region in the oncogenic actions of TRβ1 mutants. Remarkably, these C-terminal mutants induced similar growth of tumors in mouse xenograft models. Molecular analyses showed that they physically interacted with the p85α regulatory subunit of PI3K similarly in cells. In vitro GST-binding assay showed that they bound to the C-terminal Src-homology 2 (CSH2) of p85α with markedly higher avidity. The sustained association of mutants with p85α led to activation of the common PI3K-AKT-ERK/STAT3 signaling to promote cell proliferation and invasion and to inhibit apoptosis. Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence. Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis. Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

No MeSH data available.


Related in: MedlinePlus

Comparison of cell proliferation by immunohistochemical analysis using the Ki-67 marker in tumor cells derived from Neo control cells, MDA-TRβ1, MDA-PV, MDA-Mkar, MDA-Mdbs, or MDA-AM cellsA. Immunohistochemical analysis of protein abundance of the nuclear proliferation marker Ki-67 in tumors. Sections of tumors derived from Neo control cells (panels a & b), MDA-TRβ1cells (panels c & d), MDA-PV cells (panels e & f), MDA-Mkar cells (panels g & h), MDA-Mdbs cells (panels i & j), and MDA-AM cells (panels k & l) were treated with control anti-IgG (panel a, c, e, g, i, & k) or with anti Ki-67 antibodies (panel b, d, f, h, j, & l) as described in Materials and Methods. The Ki-67 positively stained cells are indicated by arrows. B. The Ki-67-positive cells were counted from three different sections and expressed as percentage of Ki-67-positive cells versus total cells examined. The data are expressed as mean ± SE (n = 3). The p-values are shown.
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Figure 5: Comparison of cell proliferation by immunohistochemical analysis using the Ki-67 marker in tumor cells derived from Neo control cells, MDA-TRβ1, MDA-PV, MDA-Mkar, MDA-Mdbs, or MDA-AM cellsA. Immunohistochemical analysis of protein abundance of the nuclear proliferation marker Ki-67 in tumors. Sections of tumors derived from Neo control cells (panels a & b), MDA-TRβ1cells (panels c & d), MDA-PV cells (panels e & f), MDA-Mkar cells (panels g & h), MDA-Mdbs cells (panels i & j), and MDA-AM cells (panels k & l) were treated with control anti-IgG (panel a, c, e, g, i, & k) or with anti Ki-67 antibodies (panel b, d, f, h, j, & l) as described in Materials and Methods. The Ki-67 positively stained cells are indicated by arrows. B. The Ki-67-positive cells were counted from three different sections and expressed as percentage of Ki-67-positive cells versus total cells examined. The data are expressed as mean ± SE (n = 3). The p-values are shown.

Mentions: The slow growth in tumors derived from MDA-TRβ1 cells could be due to decreased cell proliferation and/or increased apoptosis. We, therefore, explored these two possibilities by immunohistochemical analysis. Figure 5A compares the number of cells positively stained by the nuclear proliferation marker Ki-67. Compared with the control Neo tumor cells, tumor cells from the MDA-TRβ1 cell line had markedly fewer cells positively stained with Ki-67 (compare panel d with b). On the other hand, compared with the tumor cells from the MDA-TRβ1 cell line (panel d), tumor cells from MDA-PV (panel f), MDA-Mkar (panel h), MDA-Mdbs (panel j), and MDA-AM (panel l) cell lines all had many more cells positively stained with Ki-67. The number of cells positively stained with Ki-67 were counted and expressed as % of total cell number counted in the entire field (Figure 5B). It is clear that a significant 25% lower number of cells were stained in TRβ1 tumors than in Neo control cells (bar 2 vs. bar 1). However, tumor cells from PV, Mkar, Mdbs, and AM had as many positively stained cells as in the Neo control cells (bars 3, 4, 5, and 6). Panels a, c, e, g, j, and k are the respective negative controls for tumors from Neo control, TRβ, PV, Mkar, Mdbs, and AM cells in which no primary antibodies were used in the experiments. These results indicate that consistent with the cell-based studies shown above, mutations in the C-terminal helix 11 and 12 led to loss of inhibitory activity of cell proliferation by TRβ1 in vivo.


Oncogenic mutations of thyroid hormone receptor β.

Park JW, Zhao L, Willingham M, Cheng SY - Oncotarget (2015)

Comparison of cell proliferation by immunohistochemical analysis using the Ki-67 marker in tumor cells derived from Neo control cells, MDA-TRβ1, MDA-PV, MDA-Mkar, MDA-Mdbs, or MDA-AM cellsA. Immunohistochemical analysis of protein abundance of the nuclear proliferation marker Ki-67 in tumors. Sections of tumors derived from Neo control cells (panels a & b), MDA-TRβ1cells (panels c & d), MDA-PV cells (panels e & f), MDA-Mkar cells (panels g & h), MDA-Mdbs cells (panels i & j), and MDA-AM cells (panels k & l) were treated with control anti-IgG (panel a, c, e, g, i, & k) or with anti Ki-67 antibodies (panel b, d, f, h, j, & l) as described in Materials and Methods. The Ki-67 positively stained cells are indicated by arrows. B. The Ki-67-positive cells were counted from three different sections and expressed as percentage of Ki-67-positive cells versus total cells examined. The data are expressed as mean ± SE (n = 3). The p-values are shown.
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Figure 5: Comparison of cell proliferation by immunohistochemical analysis using the Ki-67 marker in tumor cells derived from Neo control cells, MDA-TRβ1, MDA-PV, MDA-Mkar, MDA-Mdbs, or MDA-AM cellsA. Immunohistochemical analysis of protein abundance of the nuclear proliferation marker Ki-67 in tumors. Sections of tumors derived from Neo control cells (panels a & b), MDA-TRβ1cells (panels c & d), MDA-PV cells (panels e & f), MDA-Mkar cells (panels g & h), MDA-Mdbs cells (panels i & j), and MDA-AM cells (panels k & l) were treated with control anti-IgG (panel a, c, e, g, i, & k) or with anti Ki-67 antibodies (panel b, d, f, h, j, & l) as described in Materials and Methods. The Ki-67 positively stained cells are indicated by arrows. B. The Ki-67-positive cells were counted from three different sections and expressed as percentage of Ki-67-positive cells versus total cells examined. The data are expressed as mean ± SE (n = 3). The p-values are shown.
Mentions: The slow growth in tumors derived from MDA-TRβ1 cells could be due to decreased cell proliferation and/or increased apoptosis. We, therefore, explored these two possibilities by immunohistochemical analysis. Figure 5A compares the number of cells positively stained by the nuclear proliferation marker Ki-67. Compared with the control Neo tumor cells, tumor cells from the MDA-TRβ1 cell line had markedly fewer cells positively stained with Ki-67 (compare panel d with b). On the other hand, compared with the tumor cells from the MDA-TRβ1 cell line (panel d), tumor cells from MDA-PV (panel f), MDA-Mkar (panel h), MDA-Mdbs (panel j), and MDA-AM (panel l) cell lines all had many more cells positively stained with Ki-67. The number of cells positively stained with Ki-67 were counted and expressed as % of total cell number counted in the entire field (Figure 5B). It is clear that a significant 25% lower number of cells were stained in TRβ1 tumors than in Neo control cells (bar 2 vs. bar 1). However, tumor cells from PV, Mkar, Mdbs, and AM had as many positively stained cells as in the Neo control cells (bars 3, 4, 5, and 6). Panels a, c, e, g, j, and k are the respective negative controls for tumors from Neo control, TRβ, PV, Mkar, Mdbs, and AM cells in which no primary antibodies were used in the experiments. These results indicate that consistent with the cell-based studies shown above, mutations in the C-terminal helix 11 and 12 led to loss of inhibitory activity of cell proliferation by TRβ1 in vivo.

Bottom Line: Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence.Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis.Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.

ABSTRACT
The C-terminal frame-shift mutant of the thyroid hormone receptor TRβ1, PV, functions as an oncogene. An important question is whether the oncogenic activity of mutated TRβ1 is uniquely dependent on the PV mutated sequence. Using four C-terminal frame-shift mutants-PV, Mkar, Mdbs, and AM-we examined that region in the oncogenic actions of TRβ1 mutants. Remarkably, these C-terminal mutants induced similar growth of tumors in mouse xenograft models. Molecular analyses showed that they physically interacted with the p85α regulatory subunit of PI3K similarly in cells. In vitro GST-binding assay showed that they bound to the C-terminal Src-homology 2 (CSH2) of p85α with markedly higher avidity. The sustained association of mutants with p85α led to activation of the common PI3K-AKT-ERK/STAT3 signaling to promote cell proliferation and invasion and to inhibit apoptosis. Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence. Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis. Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

No MeSH data available.


Related in: MedlinePlus