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Centrosome anomalies contribute to tumorigenesis, but it remains unclear how they are generated in lethal cancer phenotypes. Here, it is demonstrated that human microsatellite instable (MSI) and BRAFV600E-mutant colorectal cancers with a lethal rhabdoid phenotype are characterized by inactivation of centrosomal functions. A splice site mutation that causes an unbalanced dosage of rootletin (CROCC), a centrosome linker component required for centrosome cohesion and separation at the chromosome 1p36.13 locus, resulted in abnormally shaped centrosomes in rhabdoid cells from human colon tissues. Notably, deleterious deletions at 1p36.13 were recurrent in a subgroup of BRAFV600E-mutant and microsatellite stable (MSS) rhabdoid colorectal cancers, but not in classical colorectal cancer or pediatric rhabdoid tumors. Interfering with CROCC expression in near-diploid BRAFV600E-mutant/MSI colon cancer cells disrupts bipolar mitotic spindle architecture, promotes tetraploid segregation errors, resulting in a highly aggressive rhabdoid-like phenotype in vitro. Restoring near-wild-type levels of CROCC in a metastatic model harboring 1p36.13 deletion results in correction of centrosome segregation errors and cell death, revealing a mechanism of tolerance to mitotic errors and tetraploidization promoted by deleterious 1p36.13 loss. Accordingly, cancer cells lacking 1p36.13 display far greater sensitivity to centrosome spindle pole stabilizing agents in vitro. These data shed light on a previously unknown link between centrosome cohesion defects and lethal cancer phenotypes providing new insight into pathways underlying genome instability.Implications: Mis-segregation of chromosomes is a prominent feature of chromosome instability and intratumoral heterogeneity recurrent in metastatic tumors for which the molecular basis is unknown. This study provides insight into the mechanism by which defects in rootletin, a centrosome linker component causes tetraploid segregation errors and phenotypic transition to a clinically devastating form of malignant rhabdoid tumor. Mol Cancer Res; 16(9); 1385–95. ©2018 AACR.

Supplementary Table 1. Clinicopathological, immunohistochemical and molecular features of the 12 rhabdoid colorectal cancers7 Supplementary Table 2. Somatic mutations of candidate genes (15 out of 20 are reported) shared by the two rhabdoid cancers at exome sequencing Supplementary Table 3. Rhabdoid colorectal cancers (RC): molecular alterations, centrosome aberrations and ploidy Supplementary Table 4. Rhabdoid tumours of infants (RI): molecular alterations, centrosome aberrations, and ploidy Supplementary Table 5: Clinicopathologic and molecular features of classical colorectal cancers analyzed Supplementary Table 6. Sequencing and Reverse transcription PCR primers Supplementary Table 6B. SMARCB1 regions covered by the custom panel used for next-generation target sequencing Supplementary Table 7. CROCC regions covered by the custom panel used for next-generation targeted sequencing Supplementary Table 8. Antibodies employed and working conditions for immunohistochemistry, immunofluorescence or western blot analysis of tissues and cell lines Supplementary Table 9. Rhabdoid colorectal cancer reported in literature between 1993-2015

The file contains supplementary Materials and Methods

S1. Whole exome sequencing analysis of two rhabdoid colorectal cancers (RC). S2. Non-silent somatic mutations in rhabdoid tumours are enriched in centrosome-microtubule components. S3. Effect of CROCC mutations on centrosome phenotype. S4. CROCC expression profiling in classical colorectal cancers (CRCs). S5. Allelic loss at the 1p36.13 locus correlates with chromosomal instability in colorectal cancer cells. S6. Centrosome and chromosome instability in colorectal cancer cells. S7. Mitotic errors and impaired cell cycle caused by stable CROCC depletion in RKO cells. S8. Invasive behavior of colorectal cancer cells triggered by CROCC depletion. S9. Mitotic aberrations suppressed by CROCC or microtubule stabilizing agents in metastatic T84 and HT29 colorectal cancer cells.