Mesenchymal stem cells immortalization's and state-of-art: a systematic review and meta-analysis

Background

The immortalization of mesenchymal stem cells (MSCs) allows them to avoid senescence and be cultured through limitless cell passages. Thus, several experimental strategies, such as retrovirus-mediated gene transfer or viral oncogenesis, have been applied for the immortalization of MSCs. The aim was to identifier the most commonly used methodologies and their particularities for the immortalization of human and animal MSCs.

Methods

The search was conducted in June 2019 and developed in SCOPUS, PUBMED, and SCIENCE DIRECT. Statistical analysis was performed, obtaining the values of total n, mean and standard deviation, confidence interval (CI), and percentage (frequency) for all the predictors.

Results

The most used immortalization methodology was viral transfection, being the most common immortalized cell type was the bone marrow-derived MSC, and the most used gene for immortalizing both human and animal MSCs was hTERT (39.3%) and SV40T (54.5%). Among the articles analyzed in this review, only 39.3% and 36.4% of human and animal MSCs immortalization protocols, respectively, underwent the tumorigenicity test.

Conclusions

The virus-mediated gene transfection was observed as the most used and established technique. The insertion of the hTERT gene is still the most used gene for cell immortalization, suggesting that the maintenance of telomerase is efficient for maintaining cell proliferation and bypassing cell senescence. The review concluded that the tumorigenicity tests should become mandatory in order to safely use the immortalized MSCs for translation.

Abstract P5-07-03: The nuclear coactivator amplified in breast cancer 1 maintains tumor initiating cells during development of ductal carcinoma in situ

Introduction: Ductal Carcinoma In Situ (DCIS) has become the most diagnosed breast tumor type in North America. Amplified In Breast Cancer 1 (AIB1) is amplified in 5 to 10% of primary breast tumors. We have recently demonstrated that AIB1 causes development of DCIS lesions in the mammary gland of 30% of the AIB1 transgenic mice. Our laboratory has also shown that deletion of one allele of AIB1 prevents HER2-induced mammary tumor development in mice, suggesting a pivotal role of AIB1 during earlier stage of breast cancer. We hypothesize that AIB1-mediated pathways promote the transformation of the mammary epithelial cells and the alterations of the functional integrity of the mammary gland. By contrast, decrease in AIB1 functionality may result in prevented DCIS initiation and development.

Results: We show by immunohistochemistry that AIB1 is expressed at low levels in normal breast but is highly expressed in DCIS lesions. We investigated the impact of decreasing AIB1 expression on the early transformed MCFDCIS cell line. MCFDCIS cells generate multiacinar disorganized structures with filling of the lumen, loss of polarization and escape from the proliferative suppression. Reduction of AIB1 in human MCFDCIS cells restored a more normal mammary acinar structure with basement membrane in 3D growth in Matrigel. Then, we studied the effect of regulating AIB1 on the histopathology development of the DCIS lesions both prior to DCIS development or in existing MCFDCIS lesions in a xenograft mouse model by subcutaneously injecting MCFDCIS cells deficient or not in AIB1 into nude mice. The MCFDCIS xenografted tumors obtained reproduced the human breast cancer progression and displayed multiple comedo DCIS-like lesions. Decreased levels of AIB1 in MCFDCIS cells, inhibited tumor growth and led to smaller, necrotic lesions. To investigate how AIB1 affects initiation and progression of DCIS, we compared global gene expression changes in MCFDCIS cells +/-AIB1 shRNA in vitro using cDNA array analysis. Among the most significant expression changes observed were genes that are differentially expressed in Breast Cancer Initiating Cells (BCIC) including CD24 and members of the NOTCH signaling pathway (DLL1 and DLL3). We demonstrated by flow cytometric and immunohistochemical analysis that AIB1 reduction in MCFDCIS cells was correlated with significant reduction in the CD24-/CD44+ BCIC population, and a decrease in myoepithelial progenitor cells in the DCIS lesions in vitro and in vivo. Loss of AIB1 in MCFDCIS cells was also accompanied by a loss of expression of NOTCH 2, 3 and 4, JAG2, HES1, GATA3, HER2 and HER3 in vivo.

Conclusions: These data indicate that AIB1 plays a central role in the initiation and maintenance of DCIS and that reduction of AIB1 causes loss of BCIC, loss of components of the NOTCH, HER2 and HER3 signaling pathways and fewer DCIS myoepithelial progenitor cells in vivo. We propose that increased expression of AIB1, through maintenance of BCIC, facilitates formation of DCIS, a necessary step prior to development of invasive disease. Thus, targeting AIB1 may represent a new therapeutic paradigm especially for women with AIB1-positive primary tumor.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-07-03.

3p partial trisomy and 13q partial monosomy with congenital malformations and psychomotor developmental delay

We examined a girl presenting neuropsychomotor developmental delay and multiple malformations including antenatal and postnatal growth retardation, congenital heart defect, and facial dysmorphisms. Cytogenetic analysis was performed on peripheral blood lymphocytes with the GTG-banding technique, which revealed an unbalanced translocation: 46,XX,der(13)(13pter→13q34::3p24→3pter)pat. Karyotype analysis of the father demonstrated a balanced translocation, 46,XY,t(3;13)(p24;q34), indicating the inheritance of the derivative chromosome 13. The mother karyotype was normal. We suggest that most of the structural malformations seen in this patient are due to the 3p trisomy, while the neuropsychomotor alterations are a consequence of both chromosome aberrations.

The nuclear coactivator amplified in breast cancer 1 maintains tumor-initiating cells during development of ductal carcinoma in situ

The key molecular events required for the formation of Ductal Carcinoma in Situ (DCIS) and its progression to invasive breast carcinoma have not been defined. Here we show that the nuclear receptor coactivator Amplified In Breast cancer 1 (AIB1) is expressed at low levels in normal breast but is highly expressed in DCIS lesions. This is of significance since reduction of AIB1 in human MCFDCIS cells restored a more normal 3D mammary acinar structure. Reduction of AIB1 in MCFDCIS cells, both prior to DCIS development or in existing MCFDCIS lesions in vivo, inhibited tumor growth and led to smaller, necrotic lesions. AIB1 reduction in MCFDCIS cells was correlated with significant reduction in the CD24−/CD44+ Breast Cancer Initiating Cells (BCIC) population, and a decrease in myoepithelial progenitor cells in the DCIS lesions in vitro and in vivo. Loss of AIB1 in MCFDCIS cells was also accompanied by a loss of expression of NOTCH 2, 3 and 4, JAG2, HES1, GATA3, HER2 and HER3 in vivo. These signaling molecules have been associated with differentiation of breast epithelial progenitor cells. These data indicate that AIB1 plays a central role in the initiation and maintenance of DCIS and that reduction of AIB1 causes loss of BCIC, loss of components of the NOTCH, HER2 and HER3 signaling pathways and fewer DCIS myoepithelial progenitor cells in vivo. We propose that increased expression of AIB1, through maintenance of BCIC, facilitates formation of DCIS, a necessary step prior to development of invasive disease.

Frequent loss of the BLID gene in early-onset breast cancer

The BH3-like motif-containing inducer of cell death (BLID) is an intronless gene localized on 11q24.1. Loss of that region has frequently been reported in early-onset breast cancer and is significantly associated with poor prognosis and reduced survival. Downregulation of BLID is associated with younger age, triple-negative phenotype, and reduced disease-free and overall survival of breast cancer patients. In this study, we investigated allelic loss of BLID in breast tumor specimens from 78 women with invasive breast cancer using 2 dinucleotide polymorphic markers closely linked to the BLID gene (no intragenic marker for BLID is available). Seventy-three cases were informative. Overall, loss of heterozygosity (LOH) at the BLID locus was detected in 32% of the informative cases (23/73). However, in patients 40 years old and younger, LOH was detected in 50% of the cases (9/18). Patients aged 40 years and younger were significantly more likely to experience LOH than those aged 41-55 years (p = 0.04). Specifically, the odds of BLID loss for patients aged 40 years and younger were 3.7 times the odds of loss for patients aged 41-55 years (95% CI, 1.1-13). Our findings suggest a tumor suppressor role of the BLID gene in early-onset breast cancer.

Multicolour FISH and quantitative PCR can detect submicroscopic deletions in holoprosencephaly patients with a normal karyotype

Holoprosencephaly (HPE) is the most common structural malformation of the developing forebrain. At birth, nearly 50% of children with HPE have cytogenetic anomalies. Approximately 20% of infants with normal chromosomes have sequence mutations in one of the four main HPE genes (SHH, ZIC2, SIX3, and TGIF). The other non-syndromic forms of HPE may be due to environmental factors or mutations in other genes, or potentially due to submicroscopic deletions of HPE genes. We used two complementary assays to test for HPE associated submicroscopic deletions. Firstly, we developed a multicolour fluorescent in situ hybridisation (FISH) assay using probes for the four major HPE genes and for two candidate genes (DISP1 and FOXA2). We analysed lymphoblastoid cell lines (LCL) from 103 patients who had CNS findings of HPE, normal karyotypes, and no point mutations, and found seven microdeletions. We subsequently applied quantitative PCR to 424 HPE DNA samples, including the 103 samples studied by FISH: 339 with CNS findings of HPE, and 85 with normal CNS and characteristic HPE facial findings. Microdeletions for either SHH, ZIC2, SIX3, or TGIF were found in 16 of the 339 severe HPE cases (that is, with CNS findings; 4.7%). In contrast, no microdeletion was found in the 85 patients at the mildest end of the HPE spectrum. Based on our data, microdeletion testing should be considered as part of an evaluation of holoprosencephaly, especially in severe HPE cases.

Loss of heterozygosity of the BRCA1 and FHIT genes in patients with sporadic breast cancer from Southern Brazil

AIM

The evaluation of allelic losses at the FHIT and the BRCA1 genes and at three other loci at the 17q region in a series of 34 sporadic breast cancer cases from Southern Brazil.

METHODS

The samples were evaluated for loss of heterozygosity (LOH) at the FHIT and the BRCA1 genes and at three other microsatellite markers at 17q, and the findings were correlated with clinicopathological parameters.

RESULTS

The BRCA1 intragenic marker, D17S855, had the highest frequency of LOH, detected in 10 of 24 informative cases, followed by the D17S579 (six of 23 informative cases), D17S806 (five of 21 informative cases), and D17S785 markers (five of 21 informative cases). LOH at the FHIT intragenic marker, D3S1300, was found in six of 25 informative cases. In four of the six cases with LOH of the FHIT gene, there was concomitant loss of the BRCA1 intragenic marker.

CONCLUSIONS

The frequency of allelic losses in the FHIT and BRCA1 loci in the Southern Brazilian population is similar to that described in the general population. No correlations were found when the total LOH frequency was compared with tumour size, grade, or presence of axillary lymph node metastasis. Further studies using larger sporadic breast cancer samples and additional markers would be useful to confirm these findings, in addition to establishing more specific associations with clinicopathological parameters in this specific population.

Evaluation of paediatric osteosarcomas by classic cytogenetic and CGH analyses

Classic cytogenetic and comparative genomic hybridisation (CGH) data on osteosarcomas have been reported extensively in the literature. However, the number of paediatric osteosarcoma cases studied below the age of 14 years remains relatively small. This study reports four new cases of paediatric osteosarcoma in patients aged 3 to 13 years, evaluated by classic cytogenetics and CGH analyses. Clonal chromosomal alterations were detected in all the cases and included structural rearrangements at 1p11-13, 1q11, 4q27-33, 6p23-25, 6q16-25, 7p13-22, 7q11-36, 11p10-15, 11q23, 17p11.2-13, 21p11, and 21q11-22. The CGH analysis revealed recurrent gains at 1p, 4q, 17p, and 21q and losses at 3q and 16p. Five amplification sites were observed at 1q11-23, 6p21, 8q13, 8q21.3-24.2, and 17p. The data are discussed and compared with other cytogenetic reports in the literature.

Clonal chromosomal alterations in fibroadenomas of the breast

A cytogenetic study on short-term cell cultures from 10 fibroadenomas of the breast is reported. Clonal chromosomal alterations were observed in all cases analyzed, involving preferentially chromosomes X, 12, 14, 20, and 22. Normal karyotypes were found in 34.9% of the cells. The present findings are discussed together with the reports on fibroadenomas and other benign lesions of the breast described in the literature. Although no specific chromosome abnormality to date can be attributed to a particular type of benign breast pathology, some recurrent alterations are starting to emerge and may characterize these benign breast lesions, differentiating them from their malignant counterparts.

Clonal karyotypic abnormalities in gynecomastia

Gynecomastia is a benign condition that frequently occurs in the male breast gland; however, the cytogenetic data on this entity are very limited. To our knowledge, three cases have been reported in the literature, and the only one with an abnormal karyotype had a concomitant breast carcinoma. In this study we report clonal chromosomal alterations in a gynecomastia sample without any signs of adjacent malignant tissue. The nonrandom abnormalities observed were a deletion of 12p, monosomies of chromosomes 9, 17, 19, and 20, and the presence of a marker chromosome. Most of these alterations have been previously described in the literature in other breast lesions, including benign and malignant (male and female) tumors, indicating their recurrence and nonrandomness in abnormal processes of the mammary gland.

Mutagenesis, tumorigenicity, and apoptosis: are the mitochondria involved?

Early studies have shown mitochondrially-mediated oxidative phosphorylation is diminished in cancer cells, with glycolysis being the main source of energy production. More recent provocative reports have indicated that the mitochondria may be involved in a host of different aspects of tumorigenesis, including mutagenesis, maintenance of the malignant phenotype, and control of apoptosis. These studies have broadened the possible roles mitochondria may play in malignancy. Further studies to define the importance of mitochondria should revolve around the functional assessment of these changes in vitro and in vivo, and will be interesting for determining their significance in human cancer.

Cytogenetic evaluation of 20 primary breast carcinomas

Chromosome analysis was performed on samples from 20 Brazilian patients with breast cancer. All the samples were from untreated patients who presented the clinical symptoms for months or years before surgical intervention. Six cases showed axillary lymph node metastases. Clonal chromosome abnormalities were detected in all cases. The numerical alterations most frequently observed involved the loss of chromosomes X, 19, 20, and 22 followed by gain of chromosomes 9 and 8. Among the structural anomalies observed, there was preferential involvement of chromosomes 11, 6, 1, 7, 3, and 12, supporting previous reports that these chromosomes may harbour genes of importance in the development of breast tumors. Two cases with a family history of breast cancer had in common total or partial trisomy 1.

Diminished tumorigenic phenotype after depletion of mitochondrial DNA

Modulation of tumorigenicity has been considered to be a reflection of the (nuclear) genetic and cellular aberrations present in tumor cells. Recent studies have suggested that cytoplasmic elements can also contribute to the malignant phenotype of cancer, and that mitochondria may be important in this process. We, therefore, undertook a study to evaluate the effects of depletion of functional mitochondria on the tumorigenic phenotype. Brain and breast tumor cells were depleted of mitochondrial DNA [rho(-)] by treatment with ethidium bromide. These rho(-) respiratory-deficient cells showed a distinct change in the tumorigenic phenotype, including loss of ability to grow in an anchorage-independent fashion and, interestingly, a substantial increase in sensitivity to cytotoxic drugs (1,3-bis-chloroethyl-1-nitrosourea and cis-diamminedichloroplatinum(II)). Reversion to the tumorigenic phenotype was accomplished with transfer of normal mitochondria into the diminished tumorigenic rho(-) cells. No changes in expression of the apoptosis genes bcl-2 and bax, nor the drug resistance genes mdr1, mrp, or O6-alkyltransferase was found in any of the cell types (de novo, rho(-), or cybrid). Further, the type of cell death remained the same, i.e., cells with and without mitochondria underwent apoptosis in response to exposure to cytotoxic agents. Our results indicate that mitochondria/mitochondrial DNA play a direct role in modulating aspects of the tumorigenic phenotype, although they are not necessarily a sine qua non for apoptotic cell death. This is particularly interesting because most tumor tissues are more dependent upon glycolysis for energy production, rather than mitochondrially mediated oxidative phosphorylation. Creation of rho(-) cells will be useful to study the mitochondrial processes involved in tumorigenesis.

Cytogenetic report of a male breast cancer

The cytogenetic findings on G-banding in an infiltrating ductal breast carcinoma in a 69-year-old man are reported. The main abnormalities observed were trisomy of chromosomes 8 and 9 and structural rearrangement in the long arm of chromosome 17 (add(17)(q25)). Our results confirm the trisomy of chromosome 8 in the characterization of the subtype of ductal breast carcinomas and demonstrate that chromosome 17, which is frequently involved in female breast cancers, is also responsible for the development or progression of primary breast cancers in males.