Both MBC1 and MBC2 are the first breast cancer cell lines established from Malaysian primary breast cancer tissues through spontaneous immortalization. The established cell lines grow as monolayers, adherent with consistent morphologically during subsequent cultures up to 150 passages, without any changes in the epithelial morphology such as MCF-7 and MDA-MB-231. According to data on other human primary cells, the senescence period of cells undergoing cycle arrest varies from 1 to 8 weeks . However, both MBC1 and MBC2 cell lines bypassed this critical phase spontaneously after 4–5 weeks.
The MBC1 and MBC2 cell lines were able to grow in a defined DMEM medium  without any extra essential components, elements, or hormones. This is in contrast to for example, MCF-10A cell line requiring cholera toxin; MCF-7 and T-47D needing bovine insulin; and MDA-MB-435S needing ATCC-formulated Leibovitz’s L-15 Medium with bovine insulin and glutathione for growth [7, 9, 13, 14].
The more established breast cancer cell lines such as MDA-MB-231 and MCF-7 were derived from malignant effusions  which may genetically differ from the original tumour [16, 17]. However, the breast cancer cells, MBC1 and MBC2, were derived from primary infiltrating ductal breast tumours, the most frequently observed histological type . Cells derived from primary breast tumours have a lower chance of establishment compared to cell lines derived from metastatic sites or pleural effusion .
The PDT of the MBC1 cells (30.14 hrs) is comparable with the established Italian BRC-230 breast cancer cell line  and French human breast cell line VHB-1  with the PDT of 30.5 and 30 hrs, respectively; while the PDT of MBC2 (35.6 hrs) is similar to the Chinese BC-019, BC-020 breast cancer cell lines with the PDT of 36 hrs and 35 hrs, respectively . The PDT of MBC1 and MBC2 is higher than the Italian breast cancer cell lines MAST, MA2 and MA3 with a PDT of 68, 70 and 78 hrs ; the human breast cancer cell lines UACC-812 and UACC-893  with a doubling time of 100 hrs; the cell lines ZR-75-1, ZR-75-27, and ZR-75-30 from the malignant effusions of breast cancer with PDT of 80 hrs, 144 hrs and 110 hrs, respectively . According to the results obtained by other researchers, one of the main reasons for the different PDTs of cell lines is the differences in cellular content rather than differences in the rates of proliferation . The enhancement of the population doubling in vitro in the MBC1 and MBC2 human breast cell lines may be due to the existence and activity of tumourigenic stem cells  or most likely arises from the selection of faster-growing subclones from an initially heterogeneous population through frequent and incomplete trypsinisation of the cultures .
Both MBC1 and MBC2 cell lines produced a colony size of approximately 95–110 μm in diameter after day 14 on soft agar. Depending on the cell line and incubation time, different colony sizes have been reported. For instances, MCF-7 cell line forms 75–100 μm colonies after 11 days of growth and 100–200 μm in diameter by 21 days; T-47D cells form well-defined colonies with diameters of 80 μm by day 14 and 120 μm by day 21; MaTu cells grow well in soft agar with colony sizes of 50–75 μm diameters and sometimes greater than 100 μm diameters; MT-1 cells grow rapidly into colonies typically 70 μm in diameter by 11 days. However, some cell lines such as MT-3 and HS578T do not grow well in soft agar and therefore form only small colonies in the plate while some others like MC4000 cells produced no colony growth in soft agar .
Wound healing assay showed lower growth rate of the MBC2 cells compared to the MBC1 and MCF-7 as a control. The MBC1 cell line had similar growth rates with the control cell line MCF-7 in wound healing assay.
The results of entire 13 CODIS core STR loci were compared with the well-characterised and validated references provided by ATCC and JCRB, and those previously reported . The two established cell lines have neither homology to each other nor with other STR-profiled breast cell lines, demonstrating the lack of any cross-contamination of cell lines with other studied cell lines such as MCF-7 , MDA-MB-231 , HeLa, HepG2, KB and MRC-5 . DNA profiling using STR markers also confirmed the gender of tumour origin of MBC1 and MBC2 cell lines.
Expression studies revealed remarkable expression of HER2 protein in both established cell lines. The MBC1 cell line was also shown to be ER+/PR+ while the MBC2 was ER+/PR- based on mRNA expression profiling. However, the tumour origins were shown ER-/PR-/HER2- and ER-/PR-/HER2+ for the MBC1 and MBC2 cells, respectively. This may be due to a gain in secondary properties after culturing or that the MBC1 and MBC2 cells were derived from a small minority of ER+/PR+/HER2+ and ER+/PR-/HER2+ cells, respectively. The mechanism of this gain or loss during carcinogenesis is largely unknown but a very feasible hypothesis suggests a possible relationship between such deregulation and specific genetic changes .
Hence, these changes could be attributed to the Warburg effect, defined as an increased dependence on glycolysis for ATP synthesis, even in the presence of abundant oxygen, instead of a cell using the more effective pathway of OXPHOS . The Warburg effect has been consistently observed in a wide spectrum of human cancers, and has been directly linked to the activation of oncogenes, and loss of tumor suppressor genes, which result in the deregulated conversion of glucose to lactate. Among the possible mechanisms, mitochondrial malfunction and hypoxia in the tumor microenvironment are considered two major factors contributing to the Warburg effect [31, 32].
The MBC1 and MBC2 cells showed an SPF of 30.12% and 16.76% with proliferation index (PI) of 0.61 and 0.32, respectively, indicating a proportion of MBC2 cells were arrested in the G0/G1 phase, delaying the progression of the cell cycle and inhibiting cell proliferation compared to the MBC1.
The karyology study of the MBC1 and MBC2 cells demonstrated hyperdiploidy and complex rearrangement of their chromosomes. The fractured chromosomes were observed in different numbers in the MBC1 and MBC2. The hyperdiploidy (> 50 chromosomes) may arise from the fracture of the chromosomes. Cytogenetic analysis of MBC1 and MBC2 revealed an extensively rearranged hyperdiploid karyotype with unidentified chromosomes and a modal chromosome number of 52–58.