Abstract P5-10-14: Centrosome amplification score: A quantifiable cancer cell trait with putative risk-predictive value in breast cancer

Breast tumors harbor extensive intratumoral heterogeneity (ITH), both within primary and metastatic lesions. The generation of this genetic diversity relies on chromosomal instability (CIN), a dynamic and complex multilayered phenotype. CIN comprises of an increased propensity to missegregate chromosomes during mitosis and ostensibly can be regarded as a survival state adapted to aneuploidy, frequent aberrant mitosis and a sustained reshuffling of the genome. Centrosome amplification (CA), a well-established cancer cell-specific trait is known to compromise mitotic fidelity resulting in CIN. Essentially, CA assists cancer cells in concocting an array of diverse clones that drives tumor evolution by providing basic infrastructure for ITH. On this note, logical reasoning and rational thinking led us to hypothesize that CA, a cell-biological cancer cell selective feature, may be profoundly crucial and serve a causal role in driving ITH associated with tumor progression. While some studies suggest that CA is an indicator of aggressiveness, others report that extent of CA increases with grade. No study yet has ever quantified CA or emphatically demonstrated the extent of CA during the course of malignant evolution from a well differentiated to a poorly-differentiated tumor. Here we have developed first-of-a-kind novel method to quantitate the degree, extent and type of CA (both numeral and structural) within tumor samples to evaluate the trend in incidence and severity in breast tumors across grades. Tissue specimens from core biopsies of 200 breast tumors were immunostained for centrosomes and nuclei. Employing immunofluorescence confocal imaging, a stack of optical sections was acquired to capture all centrosomes and nuclei within 10 regions of interest (ROIs) per sample. Centrosomes were categorized as (i) individually-distinguishable centrosomes (iCTRs) or (ii) as megacentrosomes (mCTRs) comprised of several tightly clustered centrosomes whose precise number cannot be determined. For each ROI, number of nuclei as well as numbers and volumes of all iCTRs and mCTRs were determined and a cumulative Centrosome Amplification Score (CAS) was obtained for each ROI as CAStotal = CASi+CASm. Low grade (Grade I, n=75) tumors exhibited significantly higher CASi(3.9 vs 2.3), CASm (9.5 vs 5.4) and CAStotal (12.8 vs 8.05) values than high grade (Grade II and III, n=125) ones, which does not support the previously held notion that CA increases during disease progression. This postulation is additionally supported by the observation that low grade tumors that exhibit lymph node infiltration and metastasis (n=30) had higher CASm (7.1 vs 9.8) and CAStotal (9.5 vs 11.5) (reverse these numbers) values as compared to the non-invasive ones (n=50). In conclusion, our innovative method to quantitate CA in tumor samples establishes CA as a "quantifiable cell biological property", that can potentially predict the risk of a low grade tumor being or becoming an aggressive and invasive one. Citation Format: Vaishali Pannu, Padmashree CG Rida, Sergey Klimov, Karuna Mittal, Guilherme Cantuaria, Michelle Reid, Ritu Aneja. Centrosome amplification score: A quantifiable cancer cell trait with putative risk-predictive value in breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-10-14.