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Chemoresistance is a major challenge in effective chemotherapy for breast cancers. Unfortunately, the precise molecular mechanisms that confer resistance remain elusive so far. A remarkable feature in a multitude of breast cancers is the presence of clustered supernumerary centrosomes, which is a dysregulated condition that arises primarily through centrosome over-duplication. Normally, microtubule motor proteins (MiMos) maintain the integrity of centrosomes via regulating cohesion, separation and positioning of centrosomes. In the recent years, several MiMos have been reported to be differentially expressed in chemoresistant breast cancers. Such findings suggest a probable association of MiMos with chemoresistance. Here, we propose that MiMo-associated centrosomal dysregulation is involved in conferring chemoresistance in breast cancers. We corroborate the same with a systematic review of literature where we narrow down to sixteen MiMos (one dynein and fifteen kinesins). Our argument highlights a plausible decisive role of MiMo-mediated centrosomal anomalies in orchestrating chemoresistance in breast cancers.

The centrosome linker proteins C-Nap1, rootletin, and CEP68 connect the two centrosomes of a cell during interphase into one microtubule-organizing center. This coupling is important for cell migration, cilia formation, and timing of mitotic spindle formation. Very little is known about the structure of the centrosome linker. Here, we used stimulated emission depletion (STED) microscopy to show that each C-Nap1 ring at the proximal end of the two centrioles organizes a rootletin ring and, in addition, multiple rootletin/CEP68 fibers. Rootletin/CEP68 fibers originating from the two centrosomes form a web-like, interdigitating network, explaining the flexible nature of the centrosome linker. The rootletin/CEP68 filaments are repetitive and highly ordered. Staggered rootletin molecules (N-to-N and C-to-C) within the filaments are 75 nm apart. Rootletin binds CEP68 via its C-terminal spectrin repeat-containing region in 75-nm intervals. The N-to-C distance of two rootletin molecules is ∼35 to 40 nm, leading to an estimated minimal rootletin length of ∼110 nm. CEP68 is important in forming rootletin filaments that branch off centrioles and to modulate the thickness of rootletin fibers. Thus, the centrosome linker consists of a vast network of repeating rootletin units with C-Nap1 as ring organizer and CEP68 as filament modulator.

Genomic instability is a hallmark of cancer, and has a central role in the initiation and development of breast cancer 1 , 2 . The success of poly-ADP ribose polymerase inhibitors in the treatment of breast cancers that are deficient in homologous recombination exemplifies the utility of synthetically lethal genetic interactions in the treatment of breast cancers that are driven by genomic instability 3 . Given that defects in homologous recombination are present in only a subset of breast cancers, there is a need to identify additional driver mechanisms for genomic instability and targeted strategies to exploit these defects in the treatment of cancer. Here we show that centrosome depletion induces synthetic lethality in cancer cells that contain the 17q23 amplicon, a recurrent copy number aberration that defines about 9% of all primary breast cancer tumours and is associated with high levels of genomic instability 4 – 6 . Specifically, inhibition of polo-like kinase 4 (PLK4) using small molecules leads to centrosome depletion, which triggers mitotic catastrophe in cells that exhibit amplicon-directed overexpression of TRIM37 . To explain this effect, we identify TRIM37 as a negative regulator of centrosomal pericentriolar material. In 17q23-amplified cells that lack centrosomes, increased levels of TRIM37 block the formation of foci that comprise pericentriolar material—these foci are structures with a microtubule-nucleating capacity that are required for successful cell division in the absence of centrosomes. Finally, we find that the overexpression of TRIM37 causes genomic instability by delaying centrosome maturation and separation at mitotic entry, and thereby increases the frequency of mitotic errors. Collectively, these findings highlight TRIM37- dependent genomic instability as a putative driver event in 17q23-amplified breast cancer and provide a rationale for the use of centrosome-targeting therapeutic agents in treating these cancers. TRIM37 overexpression promotes centrosome dysfunction that drives genomic instability in breast cancer cell lines containing the recurrent 17q23 amplicon, revealing a vulnerability that can be targeted to eliminate cancer cells.

A centrosome consists of two barrel-shaped centrioles embedded in a matrix of proteins known as the pericentriolar material (PCM). The PCM serves as a platform for protein complexes that regulate organelle trafficking, protein degradation and spindle assembly. Perhaps most important for cell division, the PCM concentrates tubulin and serves as the primary organizing centre for microtubules in metazoan somatic cells. Thus, similar to other well-described organelles, such as the nucleus and mitochondria, the cell has compartmentalized a multitude of vital biochemical reactions in the PCM. However, unlike these other organelles, the PCM is not membrane bound, but rather a dynamic collection of protein complexes and nucleic acids that constitute the organelle's interior and determine its boundary. How is the complex biochemical machinery necessary for the myriad centrosome functions concentrated and maintained in the PCM? Recent advances in proteomics and RNAi screening have unveiled most of the key PCM components and hinted at their molecular interactions ( table 1). Now we must understand how the interactions between these molecules contribute to the mesoscale organization and the assembly of the centrosome. Among outstanding questions are the intrinsic mechanisms that determine PCM shape and size, and how it functions as a biochemical reaction hub.

Accurate regulation of centrosome size is essential for ensuring error-free cell division, and dysregulation of centrosome size has been linked to various pathologies, including developmental defects and cancer. While a universally accepted model for centrosome size regulation is lacking, prior theoretical and experimental works suggest a centrosome growth model involving autocatalytic assembly of the pericentriolar material. Here, we show that the autocatalytic assembly model fails to explain the attainment of equal centrosome sizes, which is crucial for error-free cell division. Incorporating latest experimental findings into the molecular mechanisms governing centrosome assembly, we introduce a new quantitative theory for centrosome growth involving catalytic assembly within a shared pool of enzymes. Our model successfully achieves robust size equality between maturing centrosome pairs, mirroring cooperative growth dynamics observed in experiments. To validate our theoretical predictions, we compare them with available experimental data and demonstrate the broad applicability of the catalytic growth model across different organisms, which exhibit distinct growth dynamics and size scaling characteristics.

Alterations in breast cancer gene 1 (BRCA1), a tumor suppressor gene, increase the risk of breast and ovarian cancers. BRCA1 forms a heterodimer with BRCA1‐associated RING domain protein 1 (BARD1) and functions in multiple cellular processes, including DNA repair and centrosome regulation. BRCA1 acts as a tumor suppressor by promoting homologous recombination (HR) repair, and alterations in BRCA1 cause HR deficiency, not only in breast and ovarian tissues but also in other tissues. The molecular mechanisms underlying BRCA1 alteration‐induced carcinogenesis remain unclear. Centrosomes are the major microtubule‐organizing centers and function in bipolar spindle formation. The regulation of centrosome number is critical for chromosome segregation in mitosis, which maintains genomic stability. BRCA1/BARD1 function in centrosome regulation together with Obg‐like ATPase (OLA1) and receptor for activating protein C kinase 1 (RACK1). Cancer‐derived variants of BRCA1, BARD1, OLA1, and RACK1 do not interact, and aberrant expression of these proteins results in abnormal centrosome duplication in mammary‐derived cells, and rarely in other cell types. RACK1 is involved in centriole duplication in the S phase by promoting polo‐like kinase 1 activation by Aurora A, which is critical for centrosome duplication. Centriole number is higher in cells derived from mammary tissues compared with in those derived from other tissues, suggesting that tissue‐specific centrosome characterization may shed light on the tissue specificity of BRCA1‐associated carcinogenesis. Here, we explored the role of the BRCA1‐containing complex in centrosome regulation and the effect of its deficiency on tissue‐specific carcinogenesis. Alterations of BRCA1, a tumor suppressor gene, increase the risk of breast and ovarian cancers. Recently, we found that BRCA1 functions in the regulation of centrosome number together with Obg‐like ATPase (OLA1) and receptor for activating protein kinase C 1 (RACK1). In this review, we explored the role of the BRCA1‐containing complex in centrosome regulation and the effect of its deficiency on tissue‐specific carcinogenesis.

The centrosome acts as the main microtubule-nucleating organelle in animal cells and plays a critical role in mitotic spindle orientation and in genome stability. Yet, despite its central role in cell biology, the centrosome is not present in all multicellular organisms or in all cells of a given organism. The main outcome of centrosome reproduction is the transmission of polarity to daughter cells and, in most animal species, the sperm-donated centrosome defines embryo polarity. Here I will discuss the role of the centrosome in cell polarity, resulting from its ability to position the nucleus at the cell center, and discuss how centrosome innovation might have been critical during metazoan evolution.

Centrosome amplification is a hallmark of cancer. However, despite significant progress in recent years, we are still far from understanding how centrosome amplification affects tumorigenesis. Boveri's hypothesis formulated more than 100 years ago was that aneuploidy induced by centrosome amplification promoted tumorigenesis. Although the hypothesis remains appealing 100 years later, it is also clear that the role of centrosome amplification in cancer is more complex than initially thought. Here, we review how centrosome abnormalities are generated in cancer and the mechanisms cells employ to adapt to centrosome amplification, in particular centrosome clustering. We discuss the different mechanisms by which centrosome amplification could contribute to tumour progression and the new advances in the development of therapies that target cells with extra centrosomes.

The centrosome is the main microtubule (MT)-organizing centre of animal cells. It consists of two centrioles and a multi-layered proteinaceous structure that surrounds the centrioles, the so-called pericentriolar material. Centrosomes promote de novo assembly of MTs and thus play important roles in Golgi organization, cell polarity, cell motility and the organization of the mitotic spindle. To execute these functions, centrosomes have to adopt particular cellular positions. Actin and MT networks and the association of the centrosomes to the nuclear envelope define the correct positioning of the centrosomes. Another important feature of centrosomes is the centrosomal linker that connects the two centrosomes. The centrosome linker assembles in late mitosis/G1 simultaneously with centriole disengagement and is dissolved before or at the beginning of mitosis. Linker dissolution is important for mitotic spindle formation, and its cell cycle timing has profound influences on the execution of mitosis and proficiency of chromosome segregation. In this review, we will focus on the mechanisms of centrosome positioning and separation, and describe their functions and mechanisms in the light of recent findings.

Owing to the frequent observation of centrosome amplification in human cancers, cancer cells have a unique mechanism to suppress detrimental multipolar division by clustering multiple centrosomes into two functional spindle poles, known as centrosome clustering. This study investigated whether inhibition of centrosome clustering enhances the radiation sensitivity of breast cancer cells. In this study, inhibition of centrosome clustering was examined by using various centrosome-declustering agents and KIFC1 siRNA in three breast cancer cell lines and two normal fibroblast cell lines. The combination effect of radiation and centrosome declustering was evaluated by cell viability, clonogenic, immunofluorescence assay. This study showed that targeting centrosome clustering enhanced the efficacy of radiotherapy of breast cancer cells with less damage to normal cells. Ionizing radiation induced centrosome amplification in breast cancer cells, but not in normal fibroblast cells. Notably, we showed that centrosome declustering efficiently radiosensitized the centrosome-amplified breast cancer cells through induction of multipolar spindles but did not affect the viability of normal fibroblasts in response to irradiation. Furthermore, KIFC1 mediated the radiosensitivity of the centrosome-amplified breast cancer cells. Our data provided the first evidence that centrosome clustering is a tumor-selective target for the improvement of radiotherapy in breast cancer cells.