Protein kinase C zeta suppresses low‐ or high‐grade colorectal cancer (CRC) phenotypes by interphase centrosome anchoring

Abstract

Histological grading provides prognostic stratification of colorectal cancer (CRC) by scoring heterogeneous phenotypes. Features of aggressiveness include aberrant mitotic spindle configurations, chromosomal breakage, and bizarre multicellular morphology, but pathobiology is poorly understood. Protein kinase C zeta (PKCz) controls mitotic spindle dynamics, chromosome segregation, and multicellular patterns, but its role in CRC phenotype evolution remains unclear. Here, we show that PKCz couples genome segregation to multicellular morphology through control of interphase centrosome anchoring. PKCz regulates interdependent processes that control centrosome positioning. Among these, interaction between the cytoskeletal linker protein ezrin and its binding partner NHERF1 promotes the formation of a localized cue for anchoring interphase centrosomes to the cell cortex. Perturbation of these phenomena induced different outcomes in cells with single or extra centrosomes. Defective anchoring of a single centrosome promoted bipolar spindle misorientation, multi‐lumen formation, and aberrant epithelial stratification. Collectively, these disturbances induce cribriform multicellular morphology that is typical of some categories of low‐grade CRC. By contrast, defective anchoring of extra centrosomes promoted multipolar spindle formation, chromosomal instability (CIN), disruption of glandular morphology, and cell outgrowth across the extracellular matrix interface characteristic of aggressive, high‐grade CRC. Because PKCz enhances apical NHERF1 intensity in 3D epithelial cultures, we used an immunohistochemical (IHC) assay of apical NHERF1 intensity as an indirect readout of PKCz activity in translational studies. We show that apical NHERF1 IHC intensity is inversely associated with multipolar spindle frequency and high‐grade morphology in formalin‐fixed human CRC samples. To conclude, defective PKCz control of interphase centrosome anchoring may underlie distinct categories of mitotic slippage that shape the development of low‐ or high‐grade CRC phenotypes. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Mechanistic Insights into Colorectal Cancer Phenomics from Fundamental and Organotypic Model Studies

“…The phenome of any tumor represents the entirety of its observable traits. In CRC, these have been intuitively categorized according to apparent biological perturbations and include the following ( Figure 1 ): i) cell cycle phenotypes such as mitotic indices and aberrant mitotic figures 16 ; ii) nuclear configurations, including size, shape, and pleomorphism 17 ; iii) cell death indices, including apoptosis, necrosis, or necroptosis; iv) functional specialization, including expression of metalloproteinases or other secreted proteins 18 ; v) cell membrane perturbations such as extensions into the stroma known as podia, 19 intracellular apical membrane (AM) vacuoles in signet-ring cancers, 20 and reversed membrane polarity 21 ; vi) multicellular arrangements, including cribriform, 10 micropapillary 21 or high-grade CRC morphology, 11 , 22 tumor budding and poorly differentiated clusters of cancer cells out with glandular structures 23 ; and vii) invasion patterns described as infiltrative or expansive. 22

Figure 1 Phenotypes within the colorectal cancer (CRC) phenome ( arrows ).

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“…Actin-dependent mechanisms generate the forces required for cell stiffening and rounding, movement of proteins within the cortex, 46 and positioning of cues for astral MT binding and centrosome stabilization. 11 , 47 These processes can also promote clustering of extra centrosomes 11 , 47 that are common in cancer cells. 48 …”

“… 74 In the sections below, we briefly review effects of M-Class or C-Class drivers or ECM factors on multiscale tissue assembly. 8 , 9 , 10 , 11 , 47 …”

“…Because the CRC genome is strongly influenced by the preexisting molecular profile of the epithelial cell of origin, 4 controls of epithelial homeostasis have been reviewed. 5 , 6 , 7 Against this background, we consider oncogenic perturbations, 8 , 9 , 10 , 11 evolution of specific CRC morphology phenotypes in culture model systems, 9 , 10 , 11 and associated translational studies. 10 , 11 Signaling nodes converge diverse molecular inputs to yield morphologically homogeneous changes 12 or, conversely, drive morphologic heterogeneity.…”

“… 5 , 6 , 7 Against this background, we consider oncogenic perturbations, 8 , 9 , 10 , 11 evolution of specific CRC morphology phenotypes in culture model systems, 9 , 10 , 11 and associated translational studies. 10 , 11 Signaling nodes converge diverse molecular inputs to yield morphologically homogeneous changes 12 or, conversely, drive morphologic heterogeneity. 1 Principles outlined may provide insight into CRC molecular subtype biology, 13 guide tumor organoid studies, 14 and aid next-generation multiplexed imaging of tumor sections.…”