Chromosome and gene alterations in breast cancer as markers for diagnosis and prognosis as well as pathogenetic targets for therapy

Recently approved treatment options for patients with metastatic triple-negative and HER2-neu-positive breast cancer

Breast cancer (BC) is the most common cancer affecting women worldwide. In 2021, the estimated number of new breast cancer cases was 281 550 and about 43 500 women died from metastatic breast cancer (mBC). For women aged 20-59 years, mBC remains the leading cause of cancer death and is, therefore, an important public health concern. Only 5% of women initially present with metastatic disease. Approximately 20% of patients presenting with local or locoregional disease progress to mBC despite adjuvant therapy. Inspite of all the medicosurgical advancements, the overall prognosis for patients diagnosed with mBC remains poor, with median overall survival of approximately 31 months, although this varies based on tumor biology. In recent years, there has been significant progress in developing immunotargeted therapies such as antihuman epidermal growth factor receptor 2 (anti-HER2) or check point inhibitors that confirmed to have dramatically improve the prognosis of mBC, a historically unfavorable disease subset. Even with the major progress that has been made in understanding the biology of BC, challenges such as resistance frequency to therapies, unknown efficacy, concerns for safety of drug combination and toxicities still remain high. Therefore, a new targeted and more selective treatment approaches are the need of the hour. In this review, we aim to outline the most recently approved medications in treatment of Her2-positive and triple-negative breast cancers.

Cat Mammary Tumors: Genetic Models for the Human Counterpart

The records are not clear, but Man has been sheltering the cat inside his home for over 12,000 years. The close proximity of this companion animal, however, goes beyond sharing the same roof; it extends to the great similarity found at the cellular and molecular levels. Researchers have found a striking resemblance between subtypes of feline mammary tumors and their human counterparts that goes from the genes to the pathways involved in cancer initiation and progression. Spontaneous cat mammary pre-invasive intraepithelial lesions (hyperplasias and neoplasias) and malignant lesions seem to share a wide repertoire of molecular features with their human counterparts. In the present review, we tried to compile all the genetics aspects published (i.e., chromosomal alterations, critical cancer genes and their expression) regarding cat mammary tumors, which support the cat as a valuable alternative in vitro cell and animal model (i.e., cat mammary cell lines and the spontaneous tumors, respectively), but also to present a critical point of view of some of the issues that really need to be investigated in future research.

Effect of low doses of estradiol and tamoxifen on breast cancer cell karyotypes

Evidence supports a role of 17&-estradiol (E2) in carcinogenesis and the large majority of breast carcinomas are dependent on estrogen. The anti-estrogen tamoxifen (TAM) is widely used for both treatment and prevention of breast cancer; however, it is also carcinogenic in human uterus and rat liver, highlighting the profound complexity of its actions. The nature of E2- or TAM-induced chromosomal damage has been explored using relatively high concentrations of these agents, and only some numerical aberrations and chromosomal breaks have been analyzed. This study aimed to determine the effects of low doses of E2 and TAM (10(&8 )mol L(&1) and 10(&6 )mol L(&1) respectively) on karyotypes of MCF7, T47D, BT474, and SKBR3 breast cancer cells by comparing the results of conventional karyotyping and multi-FISH painting with cell proliferation. Estrogen receptor (ER)-positive (+) cells showed an increase in cell proliferation after E2 treatment (MCF7, T47D, and BT474) and a decrease after TAM treatment (MCF7 and T47D), whereas in ER& cells (SKBR3), no alterations in cell proliferation were observed, except for a small increase at 96 h. Karyotypes of both ER+ and ER& breast cancer cells increased in complexity after treatments with E2 and TAM leading to specific chromosomal abnormalities, some of which were consistent throughout the treatment duration. This genotoxic effect was higher in HER2+ cells. The ER&/HER2+ SKBR3 cells were found to be sensitive to TAM, exhibiting an increase in chromosomal aberrations. These in vitro results provide insights into the potential role of low doses of E2 and TAM in inducing chromosomal rearrangements in breast cancer cells.

N-myc downstream-regulated gene 2 (NDRG2) suppresses the epithelial-mesenchymal transition (EMT) in breast cancer cells via STAT3/Snail signaling

Although NDRG2 has recently been found to be a candidate tumor suppressor, its precise role in the epithelial-mesenchymal transition (EMT) is not well understood. In the present study, we demonstrated that NDRG2 overexpression in MDA-MB-231 cells down-regulated the expression of Snail, a transcriptional repressor of E-cadherin and a key regulator of EMT, as well as the phosphorylation of signal transducer and activator of transcription 3 (STAT3), an oncogenic transcription factor that is activated in many human malignancies including breast cancer. In addition, we confirmed that the expression of Snail and phospho-STAT3 was recovered when NDRG2 was knocked down by siRNA in MCF7 cells in which NDRG2 is endogenously expressed. Interestingly, MDA-MB-231-NDRG2 cells showed remarkably decreased Snail expression after treatment with JSI-124 (also known as cucurbitacin I) or Stattic, STAT3 inhibitors, compared to MDA-MB-231-mock cells. Moreover, STAT3 activation by EGF treatment induced higher Snail expression, and NDRG2 overexpression resulted in the inhibition of Snail expression in MDA-MB-231 cells stimulated by EGF in the absence or presence of STAT3 inhibitor. Treatment of MDA-MB-231 cells with STAT3 inhibitor led to a moderate decrease in wound healing and migration capacity, whereas STAT3 inhibitor treatment of MDA-MB-231-NDRG2 cells resulted in a significant attenuation of migration in both resting and EGF-stimulated cells. Collectively, our data demonstrate that the inhibition of STAT3 signaling by NDRG2 suppresses EMT progression of EMT via the down-regulation of Snail expression.

Cellular senescence and longevity of osteophyte-derived mesenchymal stem cells compared to patient-matched bone marrow stromal cells

This study aimed to determine the cellular aging of osteophyte-derived mesenchymal cells (oMSCs) in comparison to patient-matched bone marrow stromal cells (bMSCs). Extensive expansion of the cell cultures was performed and early and late passage cells (passages 4 and 9, respectively) were used to study signs of cellular aging, telomere length, telomerase activity, and cell-cycle-related gene expression. Our results showed that cellular aging was more prominent in bMSCs than in oMSCs, and that oMSCs had longer telomere length in late passages compared with bMSCs, although there was no significant difference in telomere lengths in the early passages in either cell type. Telomerase activity was detectable only in early passage oMSCs and not in bMSCs. In osteophyte tissues telomerase-positive cells were found to be located perivascularly and were Stro-1 positive. Fifteen cell-cycle regulator genes were investigated and only three genes (APC, CCND2, and BMP2) were differentially expressed between bMSC and oMSC. Our results indicate that oMSCs retain a level of telomerase activity in vitro, which may account for the relatively greater longevity of these cells, compared with bMSCs, by preventing replicative senescence.

Molecular markers of breast axillary lymph node metastasis

In breast cancer, axillary lymph node status is one of the most important prognostic variables and a crucial component to the staging system. Several clinico-histopathological parameters are considered to be strong predictors of metastasis; however, they fail to accurately classify breast tumors according to their clinical behavior and to predict which patients will have disease recurrence. Methods based on genome-wide microarray analyses have been used to identify molecular markers with respect to the development of axillary lymph node metastasis. Most of these markers can be detected in the primary tumors, which can potentially lead to the ability to identify patients at the time of diagnosis who are at high risk for lymph node metastasis, allowing for early intervention and more suitable adjuvant treatments.

Integrated profiling of basal and luminal breast cancers

Basal and luminal are two molecular subtypes of breast cancer with opposite histoclinical features. We report a combined, high-resolution analysis of genome copy number and gene expression in primary basal and luminal breast cancers. First, we identified and compared genomic alterations in 45 basal and 48 luminal tumors by using 244K oligonucleotide array comparative genomic hybridization (aCGH). We found various genome gains and losses and rare high-level gene amplifications that may provide therapeutic targets. We show that gain of 10p is a new alteration in basal breast cancer and that a subregion of the 8p12 amplification is specific of luminal tumors. Rare high-level amplifications contained BCL2L2, CCNE, EGFR, FGFR2, IGF1R, NOTCH2, and PIK3CA. Potential gene breaks involved ETV6 and FLT3. Second, we analyzed both aCGH and gene expression profiles for 42 basal and 32 luminal breast cancers. The results support the existence of specific oncogenic pathways in basal and luminal breast cancers, involving several potential oncogenes and tumor suppressor genes (TSG). In basal tumors, 73 candidate oncogenes were identified in chromosome regions 1q21-23, 10p14, and 12p13 and 28 candidate TSG in regions 4q32-34 and 5q11-23. In luminal breast cancers, 33 potential oncogenes were identified in 1q21-23, 8p12-q21, 11q13, and 16p12-13 and 61 candidate TSG in 16q12-13, 16q22-24, and 17p13. HORMAD1 (P = 6.5 x 10(-5)) and ZNF703 (P = 7 x 10(-4)) were the most significant basal and luminal potential oncogenes, respectively. Finally, among 10p candidate oncogenes associated with basal subtype, we validated CDC123/C10orf7 protein as a basal marker.

Genomic signatures of breast cancer metastasis

Despite significant advances in the treatment of primary cancer, the ability to predict the metastatic behavior of a patient's cancer, as well as to detect and eradicate such recurrences, remain major clinical challenges in oncology. While many potential molecular biomarkers have been identified and tested previously, none have greatly improved the accuracy of specimen evaluation over routine histopathological criteria and they predict individual outcomes poorly. However, the recent introduction of high-throughput microarray technology has opened new avenues in genomic investigation of cancer, and through application in tissue-based studies and appropriate animal models, has facilitated the identification of gene expression signatures that are associated with the lethal progression of breast cancer. The use of these approaches has the potential to greatly impact our knowledge of tumor biology, to provide efficient biomarkers, and enable development towards customized prognostication and therapies for the individual.

SOCS1 induced by NDRG2 expression negatively regulates STAT3 activation in breast cancer cells

Although NDRG2 inactivation has recently been found to have an important role in some tumorigenesis, its role in intracellular signal transduction pathways remains poorly defined. In the present study, we demonstrate that NDRG2 overexpression in malignant breast cancer cells specifically inhibits Akt phosphorylation and induces phosphorylation of p38 MAP kinase and SAPK/JNK. In addition, we investigated whether NDRG2 expression affects JAK/STAT- or mitogen-activated protein kinase-mediated signal activation. JAK2 or STAT3 activation in both resting and IGF-stimulating cells was remarkably inhibited by NDRG2 expression. Furthermore, NDRG2 has been found to highly up-regulate the expression level of SOCS1 mRNA and protein. We have found that NDRG2 was able to regulate cytokine signaling in breast cancer cells through the regulation of SOCS1 expression. Finally, inhibition of p38 MAPK activity blocked the induction of SOCS1 expression by NDRG2, resulting in the recovery of STAT3 phosphorylation level. Together, these data demonstrate that NDRG2 expression in breast cancer cells is able to inhibit STAT3 activation via SOCS1 induction in a p38 MAPK dependent manner, implicating NDRG2 as a growth inhibitory gene in signal transduction pathways of breast tumor cells.

Chromosome alterations associated with positive and negative lymph node involvement in breast cancer

Genetic heterogeneity is high in breast cancer, and hence it is difficult to link a specific chromosome alteration to a specific clinicopathologic feature. We examined clonal chromosome alterations in 45 breast carcinomas and statistically correlated the findings with clinical-histopathological parameters of the patients. The most common abnormalities were losses of chromosomes 19, 22, 21, X, and 17 and gains of chromosomes 9 and 18. A statistically significant correlation was found between clonal aberrations in chromosomes 17, 20, and 21 and positive lymph node involvement (LN+) and between clonal aberrations in chromosomes X and 6 and negative involvement (LN-). The average number of chromosome abnormalities was the same for both LN- and LN+ groups, and numerical and structural alterations were equally distributed. The mean number of chromosome aberrations did not differ significantly among tumor grades, but when aberrations were analyzed as monosomies, trisomies, and structural aberrations, a heterogeneous distribution was observed. Further cytogenetic investigation of breast tumors and their variable pathological features is undoubtedly necessary. The recognition and ultimately the molecular understanding of these abnormalities may improve breast cancer taxonomy and provide important prognostic information for both the patient and clinician.

Deregulated expression of the PER1 , PER2 and PER3 genes in breast cancers

Disruption of circadian rhythm may be a risk factor in the development of breast cancer, but molecular changes in circadian rhythm controlled genes in breast cancer cells are still unexplored. We used immunohistochemical staining, methylation specific PCR and direct sequencing methods to analyze molecular changes in three most important genes, namely PER1, PER2 and PER3, in circadian rhythm in 55 cases of breast cancer of Taiwanese women. Our results reveal disturbances in the expression of the three period (PER) genes in most (>95%) of the breast cancerous cells in comparison with the nearby non-cancerous cells. The PER gene deregulation is not caused by genetic mutations but most probably by methylation of the PER1 or PER2 promoter. Methylation of the PER gene promoters has a strong correlation with c-erbB2 expression (P = 0.017). Since the circadian clock controls expression of cell-cycle related genes, we suggest that disturbances in PER gene expression may result in disruption of the control of the normal circadian clock, thus benefiting the survival of cancer cells and promoting carcinogenesis. Differential expression of circadian genes in non-cancerous and cancerous cells may provide a molecular basis for chronotherapy of breast cancer.

Molecular cytogenetic analysis of a human breast metastasis model: identification of phenotype-specific chromosomal rearrangements

We have previously characterized an experimental system in which the role of candidate metastasis-related genes can be screened and tested. Monoclonal cell lines M4A4 and NM2C5 originated from the MDA-MB-435 breast tumor cell line but have opposite metastatic capabilities in vivo. To investigate gross genetic changes present in this model, we performed a detailed molecular cytogenetic evaluation of the parental cell line, the M4A4 and NM2C5 cell lines, and related clones of metastatic phenotype. Using a combination of spectral karyotyping (SKY), G-banding, and fluorescence in situ hybridization (FISH), we were able to resolve the identity of all common marker chromosomes present in MDA-MB-435 cells, and to define several chromosomal changes, which were specific to each monoclonal cell line. Twenty identical structural and numerical chromosomal aberrations, including trisomies of chromosomes 2 and 5 as well as t(1;7), t(1;10), t(8;11), t(8;15), and t(20;21), were present in all cell lines. The majority of translocations were relatively simple non-reciprocal rearrangements, most frequently involving chromosomes 19, 1, 6, and 20. Chromosomal gains of 1, 7q, 8q, and 20q are common alterations in breast cancer. The metastatic M4A4 cell line contained numerous unique chromosomal aberrations, of which an abnormal banding region on chromosome 22, abr(22), was the best clone-specific identifier. Conversely, the t(12;15)(q22;q26.1) was found exclusively in the non-metastatic NM2C5 cell line. The integration of these karyotypic data with other cytogenetic and genomic databases will enhance our ability to identify genes that play critical roles in cancer development and progression.

Molecular cytogenetic analysis of breast cancer: a combined multicolor fluorescence in situ hybridization and G-banding study of uncultured tumor cells

In six patients with breast cancer, uncultured tumor cells were investigated with G-banding and multicolor fluorescence in situ hybridization (M-FISH). A large number of numerical and structural aberrations could be analyzed. Among other structural abnormalities, reciprocal, hidden and complex translocations were found. Recurrent t(1;10) and t(6;16), not previously described, were identified, as well as t(15;22). The latter was also found in additional cases among our unpublished breast carcinomas. The significance of t(15;22) for breast cancer is discussed, taking into account also data drawn from the literature. Reciprocal translocations were a prominent feature in a pseudodiploid lobular carcinoma. Hidden translocations on 6p22-p24 were detected with M-FISH. Involvement of 6p22-p24 was observed in five cases. The analysis of various other translocations and different structural abnormalities revealed the following common breakpoints (according to frequency of involvement): 1p34-p36, 3p12-p13, 4p13-->q11, 14p11-->q11, 1q42, 8p11, 8q24, 10q22, 11q13, 11q23-q24, 13q13, and 18p10-p11. Loss of 3p and 1p34-p36-->pter and complete or partial loss of 13q and chromosome 17 were also found. With the combination of G-banding and M-FISH techniques, chromosome misclassification is avoided and the characterization of complex tumor karyotypes is more effective.

Genetic alteration and gene expression modulation during cancer progression

Cancer progresses through a series of histopathological stages. Progression is thought to be driven by the accumulation of genetic alterations and consequently gene expression pattern changes. The identification of genes and pathways involved will not only enhance our understanding of the biology of this process, it will also provide new targets for early diagnosis and facilitate treatment design. Genomic approaches have proven to be effective in detecting chromosomal alterations and identifying genes disrupted in cancer. Gene expression profiling has led to the subclassification of tumors. In this article, we will describe the current technologies used in cancer gene discovery, the model systems used to validate the significance of the genes and pathways, and some of the genes and pathways implicated in the progression of preneoplastic and early stage cancer.

Chromosome-mediated alterations of the MYC gene in human cancer

The step-wise accumulation of genetic and epigenetic alterations in cancer development includes chromosome rearrangements and viral integration-mediated genetic alterations that frequently involve proto-oncogenes. Proto-oncogenes deregulation lead to unlimited, self-sufficient cell growth and ultimately generates invasive and destructive tumors. C-MYC gene, the cellular homologue of the avian myelocitic leukemia virus, is implicated in a large number of human solid tumors, leukemias and lymphomas as well as in a variety of animal neoplasias. Deregulated MYC expression is a common denominator in cancer. Chromosomal rearrangements and integration of oncogenic viruses frequently target MYC locus, causing structural or functional alterations of the gene. In this article, we illustrate how genomic rearrangements and viruses integration affect MYC locus in certain human lymphomas and solid tumors.