Modified cIg-FISH protocol for multiple myeloma in routine cytogenetic laboratory practice

Modeling multiple myeloma-bone marrow interactions and response to drugs in a 3D surrogate microenvironment

Multiple myeloma develops primarily inside the bone marrow microenvironment, that confers pro-survival signals and drug resistance. 3D cultures that reproduce multiple myeloma-bone marrow interactions are needed to fully investigate multiple myeloma pathogenesis and response to drugs. To this purpose, we exploited the 3D Rotary Cell Culture System bioreactor technology for myeloma-bone marrow co-cultures in gelatin scaffolds. The model was validated with myeloma cell lines that, as assessed by histochemical and electron-microscopic analyses, engaged contacts with stromal cells and endothelial cells. Consistently, pro-survival signaling and also cell adhesion-mediated drug resistance were significantly higher in 3D than in 2D parallel co-cultures. The contribution of the VLA-4/VCAM1 pathway to resistance to bortezomib was modeled by the use of VCAM1 transfectants. Soluble factor-mediated drug resistance could be also demonstrated in both 2D and 3D co-cultures. The system was then successfully applied to co-cultures of primary myeloma cells-primary myeloma bone marrow stromal cells from patients and endothelial cells, allowing the development of functional myeloma-stroma interactions and MM cell long-term survival. Significantly, genomic analysis performed in a high-risk myeloma patient demonstrated that culture in bioreactor paralleled the expansion of the clone that ultimately dominated in vivo. Finally, the impact of bortezomib on myeloma cells and on specialized functions of the microenvironment could be evaluated. Our findings indicate that 3D dynamic culture of reconstructed human multiple myeloma microenvironments in bioreactor may represent a useful platform for drug testing and for studying tumor-stroma molecular interactions.

Comparison of Diagnostic Yield of a FISH Panel Against Conventional Cytogenetic Studies for Hematological Malignancies: A South Indian Referral Laboratory Analysis Of 201 Cases

Objectives:

Genetic markers are crucial fort diagnostic and prognostic investigation of hematological malignancies (HM). The conventional cytogenetic study (CCS) has been the gold standard for more than five decades. However, FISH (Fluorescence in Situ Hybridization) testing has become a popular modality owing to its targeted approach and the ability to detect abnormalities in non-mitotic cells. We here aimed to compare the diagnostic yields of a FISH panel against CCS in HMs.

Methods:

Samples of bone marrow and peripheral blood for a total of 201 HMs were tested for specific gene rearrangements using multi-target FISH and the results were compared with those from CCS.

Results:

Exhibited a greater diagnostic yield with a positive result in 39.8% of the cases, as compared to 17.9% of cases detected by CCS. Cases of chronic lymphocytic leukaemia (CLL) benefited the most by FISH testing, which identified chromosomal aberrations beyond the capacity of CCS. FISH was least beneficial in myelodysplastic syndrome (MDS) where the highest concordance with CCS was exhibited. Acute lymphocytic leukaemia (ALL) demonstrated greater benefit with CCS. In addition, we found the following abnormalities to be most prevalent in HMs by FISH panel testing: RUNX1 (21q22) amplification in ALL, deletion of D13S319/LAMP1 (13q14) in CLL, CKS1B (1q21) amplification in multiple myeloma and deletion of EGR1/RPS14 (5q31/5q32) in MDS, consistent with the literature.

Conclusions:

In conclusion, FISH was found to be advantageous in only a subset of HMs and cannot completely replace CCS. Utilization of the two modalities in conjunction or independently should depend on the indicated HM for an optimal approach to detecting chromosomal aberrations.

Target fluorescence in-situ hybridization (Target FISH) for plasma cell enrichment in myeloma

BACKGROUND

Cytogenetic abnormalities are important prognostic markers in plasma cell myeloma (PCM) and detection is routinely performed by interphase fluorescence in-situ hybridization (FISH) with a panel of probes after enrichment of the plasma cells in the bone marrow specimen. Cell sorting by immunomagnetic beads and concurrent labeling of the cytoplasmic immunoglobulin are the usual enrichment methods. We present an alternative method of plasma cell enrichment termed Target FISH, which is an automated system that combines the images of May-Grünwald- Giemsa (MGG) staining and FISH study on the same plasma cell for analysis.

RESULTS

Our experience of Target FISH on 40 PCM patients was described. Briefly, plasma cells were MGG stained, image captured, de-stained, FISH probe hybridized and finally relocated for simultaneous analysis of morphology and FISH signal pattern. The FISH probe panel was TP53/CEP17, t(4;14) IGH/FGFR3, t(14;16) IGH/MAF and CKS1B(1q21)/CDKN2C(P18). Gain of 1q21 was the most common abnormality detected in 18 patients (45 %), to be followed by t(4;14) IGH/FGFR3 detected in 11 patients (27.5 %). Of note, 10 patients showed coexistence of both t(4;14) and 1q21 gain. Two patients showed del(17p)/TP53, one in association with t(4;14) and 1q gain while the other was stand alone. None of this patient cohort showed t(14;16) IGH/MAF. Using the critical binomial function, the normal cutoff FISH positive value for del(17p)/TP53 was 3.4 %, t(4;14) IGH/FGFR3 was 6.8 %, t(14;16) IGH/MAF was 5.6 % and +1q21 was 5.7 %.

CONCLUSIONS

The equipment cost notwithstanding, when compared with cell sorting, the total reagent cost was around 10 % lower in Target FISH. The total processing time was longer for Target FISH but manual fluorescence microscopy was no longer necessary. The main advantage of Target FISH was the complete certainty that the cytogenetic abnormality was detected in the cells of interest, and hence a more stringent analytical cutoff value might be considered. Optimization of the cell collection and slide preparation process upfront was required to accrue adequate target cells on each slide for analysis. Our experience suggested that Target FISH was applicable as a routine method of plasma cell enrichment in clinical diagnostic laboratories.