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Serine 2481-autophosphorylation of mammalian target of rapamycin (mTOR) couples with chromosome condensation and segregation during mitosis: Confocal microscopy characterization and immunohistochemical validation of PP-mTORSer2481 as a novel high-contrast mitosis marker in breast cancer core biopsies

  • Authors:
    • Eugeni Lopez-Bonet
    • Alejandro Vazquez-Martin
    • Maria Carmen Pérez-Martínez
    • Cristina Oliveras-Ferraros
    • Ferran Pérez-Bueno
    • Luis Bernadó
    • Javier A. Menendez
  • View Affiliations

  • Published online on: January 1, 2010     https://doi.org/10.3892/ijo_00000481
  • Pages: 107-115
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Abstract

The prognostic abilities of breast cancer gene expression signatures are due mostly to the detection of proliferation activity. One of the strongest, yet simple and well-reproducible proliferation-associated prognostic factors is the mitotic activity index (MAI). However: a) counting mitotic figures is regarded by many histopathologists as cumbersome and time-consuming, and b) most available immunohistochemical markers are much weaker predictors than the MAI. We have investigated the spatio-temporal sub-cellular distribution of the Serine 2481-autophosphorylated form of mTOR (PP-mTORSer2481) during the G1/S-to-M-phase transition both in cultured cancer cells and in cancer tissue specimens. Using a high-resolution, automated confocal high-content imaging system, we observed that mitotic cells notably accumulated a distinct pattern of nuclear and cytoplasmic immunolabelings of PP-mTORSer2481. Parallel experiments examining site-specific phosphorylation (i.e., Serine 10 and Serine 28) of the G2/M marker Histone H3 (PP-H3) revealed that PP-H3Ser10/Ser28 staining efficiently detected mitotic cells from prophase until the beginning of anaphase, but not during late anaphase, telophase and cytokinesis. PP-mTORSer2481 staining associated near and between separating chromosomes not only during early mitotic stages but also to the midzone and to midbody at ana/telophase through cytokinesis. We then evaluated the usefulness of PP-mTORSer2481 immunostaining for improving the efficiency of mitotic counting using. Anti-PP-mTORSer2481-labeled mitotic figures (MFs) were easily seen and permitted a quick identification of mitotic hotspots in formalin-fixed cancer tissues, even at low magnification. Importantly, average mitotic counts were significantly higher when using PP-mTORSer2481 staining than with the hematoxylin and eosin (H&E) protocol in breast cancer core biopsies. Mitotic count based on PP-mTORSer2481 immunostaining increased tumor grade by one grade in 2 of 9 breast carcinomas. These findings warrant forthcoming studies to confirm both the accuracy and the prognostic value of PP-mTORSer2481 as a novel high-contrast immunohistochemical mitosis marker in larger populations of human breast carcinomas.

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January 2010
Volume 36 Issue 1

Print ISSN: 1019-6439
Online ISSN:1791-2423

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APA
Lopez-Bonet, E., Vazquez-Martin, A., Pérez-Martínez, M.C., Oliveras-Ferraros, C., Pérez-Bueno, F., Bernadó, L., & Menendez, J.A. (2010). Serine 2481-autophosphorylation of mammalian target of rapamycin (mTOR) couples with chromosome condensation and segregation during mitosis: Confocal microscopy characterization and immunohistochemical validation of PP-mTORSer2481 as a novel high-contrast mitosis marker in breast cancer core biopsies. International Journal of Oncology, 36, 107-115. https://doi.org/10.3892/ijo_00000481
MLA
Lopez-Bonet, E., Vazquez-Martin, A., Pérez-Martínez, M. C., Oliveras-Ferraros, C., Pérez-Bueno, F., Bernadó, L., Menendez, J. A."Serine 2481-autophosphorylation of mammalian target of rapamycin (mTOR) couples with chromosome condensation and segregation during mitosis: Confocal microscopy characterization and immunohistochemical validation of PP-mTORSer2481 as a novel high-contrast mitosis marker in breast cancer core biopsies". International Journal of Oncology 36.1 (2010): 107-115.
Chicago
Lopez-Bonet, E., Vazquez-Martin, A., Pérez-Martínez, M. C., Oliveras-Ferraros, C., Pérez-Bueno, F., Bernadó, L., Menendez, J. A."Serine 2481-autophosphorylation of mammalian target of rapamycin (mTOR) couples with chromosome condensation and segregation during mitosis: Confocal microscopy characterization and immunohistochemical validation of PP-mTORSer2481 as a novel high-contrast mitosis marker in breast cancer core biopsies". International Journal of Oncology 36, no. 1 (2010): 107-115. https://doi.org/10.3892/ijo_00000481