The Stem Cell Factor HMGA2 Is Expressed in Non-HPV-Associated Head and Neck Squamous Cell Carcinoma and Predicts Patient Survival of Distinct Subsites.

BACKGROUND: The transcription factor high-mobility AT-hook 2 (HMGA2) is involved in stem cell renewal and is expressed in many tumor tissues. Head and neck squamous cell carcinomas (HNSCC) comprise tumors of the upper aerodigestive tract and are characterized by high recurrence rates that represent a challenge to patient management. The study addresses the potential of HMGA2 as a molecular biomarker for HNSCC patient survival. METHODS: Patients with HNSCC of the larynx, pharynx, tonsils, or oral cavity were recruited in a hospital-based case-control study (n = 202). Quantitative expression of HMGA2 in tumor tissues was measured by RT-PCR. In a 6- to 10-year follow-up, secondary cancers, vital status, and cause of death were ascertained. The HR and 95% confidence intervals (CI) for overall, tumor-specific, and progression-free survival were estimated by Cox proportional hazards with HMGA2 expression level as the independent variable. RESULTS: High HMGA2 expression in tumor tissues of HNSCC patients was significantly correlated with negative HPV status (P = 0.01), and associated with shorter overall survival time. In Cox regression modeling, HMGA2 expression yielded a risk increase for overall and tumor-specific death in subsets of HNSCC patients, that is, laryngeal cancer patients (overall survival: HR = 4.00; 95% CI, 1.18-13.62) and in oral cancer patients (tumor-specific survival: HR = 2.88; 95% CI, 1.06-7.84), but not in patients with pharyngeal and tonsillar HNSCC. CONCLUSIONS: HMGA2 expression is associated with a risk increase for adverse outcomes in patients with HNSCC of the larynx and oral cavity. IMPACT: The understanding of stem cell signaling in HNSCC may offer new strategies for cancer treatment. Cancer Epidemiol Biomarkers Prev; 26(2); 197-205. ©2016 AACR.

Patterns of Chromosomal Abnormalities that Can Improve Diagnosis of Uterine Smooth Muscle Tumors.

BACKGROUND/AIM: Compared to leiomyomas, smooth muscle tumors of uncertain malignant potential (STUMP), and leiomyosarcomas (LMS) originating from the Muellerian duct are very rare. Their molecular pathogenesis remains poorly understood. The present article aims at performing genetic analyses of these tumors that may help assist histopathological examination. MATERIALS AND METHODS: Ten tumors (four STUMP and six LMS) were investigated by copy number arrays. RESULTS: Two tumors, both classified as STUMP were shown to carry MED12 mutations with one of them presenting with a detectable copy number alteration. All other tumors had multiple copy number changes with a clear predominance of losses. Five chromosomal arms (1p, 13q, 14q, 16q, 22q) were affected by overlapping lost segments in at least four tumors including two cases with biallelic losses of the retinoblastoma gene locus. CONCLUSION: Besides the general presence of copy number alterations and particular genetic alterations, heterogeneity and ongoing karyotypic evolution indicate malignancy or approaching malignancy.

A rare coincidence of different types of driver mutations among uterine leiomyomas (UL).

Mutations of mediator subcomplex 12 (MED12) and of high mobility group protein AT-hook 2 (HMGA2) are driver mutations in uterine leiomyomas (UL) that have not been observed to coexist in one tumor and even rarely coexist in different UL tumors of one patient. Here we describe a patient who underwent hysterectomy because of multiple leiomyomas which were studied by cytogenetics, MED12 hotspot sequencing, and copy number variation arrays. Two of the UL tumors had different HMGA2 rearrangements not detected by G-banding. Two UL tumors had deletions of the long arm of chromosome 3, in one case associated with a MED12 mutation. Both deletions lead to the loss of MED12L showing strong similarity with MED12. It remains to be determined if this gene can play a role in leiomyomagenesis independent of MED12. In summary, the patient presented exhibits an unusual coincidence of different driver mutations among her leiomyomas.

Cytogenetically normal uterine leiomyomas without MED12-mutations - a source to identify unknown mechanisms of the development of uterine smooth muscle tumors.

BACKGROUND: Recent findings on genetic changes in uterine leiomyomas suggest these benign tumors being a heterogeneous group of diseases in terms of molecular pathogenesis with those showing karyotype alterations as well as those characterized only by cytogenetically invisible mutations of mediator subcomplex 12 (MED12). Herein, five uterine leiomyomas (UL) with an apparently normal karyotype that lacked MED12-mutations were investigated by copy number variation arrays along with their matching myometrium to search for small genomic imbalances. RESULTS: Of five tumors one showed chromothripsis-like phenomena with numerous gains and losses of small segments mainly clustered to five chromosomal regions i.e. 2p14-2pter, 2q33.1-2q37.3, 5q31.3-5qter,11q14.1-11qter, and 18p11.21-18q2.3. Apparently, these cells had escaped detection by classical cytogenetics. Histologically, the tumor presented as a cellular leiomyoma with extended hyalinization. Of the remaining four tumors, one had a small intragenic deletion of the HMGA2 gene that was lacking in the corresponding myometrium. The other three tumors did not show relevant copy number alterations at all. CONCLUSIONS: Overall, the results suggest that leiomyomas with an apparently normal karyotype based on classical cytogenetics and lacking MED12 mutations represent a heterogeneous group of diseases. While the HMGA2 deletion detected in one of the tumors likely represents the driver mutation and, due to its size, has escaped detection by classical cytogenetics, the extended genomic imbalances detected in one of the other cases cannot be overlooked by this method suggesting an inability of the affected cells to divide in vitro. Of particular interest in that case is the occurrence of so-called "chromothripsis" or "firestorms" without involvement of the loci of common chromosomal rearrangements in UL, as e.g. 12q14 ~ 15 and 6p21. While chromothripsis was initially described as a hallmark of malignancy, the etiology and significance of this phenomenon in benign tumors still remain obscure. In uterine smooth muscle tumors, these changes per se do not indicate malignancy.

Genome-wide acquired uniparental disomy as well as chromosomal gains and losses in an uterine epithelioid leiomyoma.

BACKGROUND: Epitheloid leiomyoma is a rare subtype of benign smooth muscle tumors. RESULTS: Herein, we present the results of classical cytogenetics, MED12 mutation analysis, and copy number variation array evaluation in one such case. Whereas cytogenetic did not show evidence for clonal chromosome abnormalities and no MED12 mutation in the "fibroid hot spot" region was detected, array hybridization revealed multiple abnormalities. Most noteworthy, almost all chromosomes showed copy-number neutral loss of heterozygosity. As examples of further abnormalities, trisomies of chromosomes 8, 12, 20, and X were noted. DISCUSSION: The data presented suggest a near-haploid karyotype of the tumor as the initial genetic alteration followed by secondary duplications of large parts of the genome. The absence of any clonal karyotypic alterations after performing classical cytogenetics is likely explained by a reduced ability of the tumor cells to proliferate in vitro. However, to the best of our knowledge this is the first report of an uterine leiomyoma showing extended uniparental disomy. It remains to be determined if this is a more common phenomenon in epithelioid leiomyomas or even subsets of "ordinary" leiomyomas.

The CD24hi smooth muscle subpopulation is the predominant fraction in uterine fibroids.

Uterine fibroids are the most common gynecological tumors affecting women in their reproductive age. Despite this high incidence the pathogenesis of fibroids is widely unsolved. Whereas formerly only imbalances in hormonal levels were considered to account for tumor development, the identification of genetic changes likely to affect myometrial stem cell reservoirs provided a novel approach to fibroid genesis. Here, we identified a certain subset of cells by the surface marker CD24 with increased abundance in fibroids compared with myometrial tissue. Fibroid cells expressing CD24 shared certain features of immature or progenitor-like cells such as quiescence, reduced expression of smooth muscle differentiation markers and elevated expression of genes involved in the wingless-type (WNT)-pathway such as beta-catenin. In addition, a positive correlation between CD24 and wingless-type family member 4 (WNT4) expression was observed in uterine fibroids with mediator subcomplex 12 gene (MED12) mutations. Our findings suggest that cells highly expressing CD24 represent a type of immature smooth muscle progenitor cells. Their accumulation might be driven by disturbed differentiation processes caused by genetic changes possibly involving MED12 mutations or high mobility group AT-hook (HMGA)2 rearrangements.

Correlated expression of HMGA2 and PLAG1 in thyroid tumors, uterine leiomyomas and experimental models.

In pleomorphic adenomas of the salivary glands (PASG) recurrent chromosomal rearrangements affecting either 8q12 or 12q14∼15 lead to an overexpression of the genes of the genuine transcription factor PLAG1 or the architectural transcription factor HMGA2, respectively. Both genes are also affected by recurrent chromosomal rearrangements in benign adipocytic tumors as e. g. lipomas and lipoblastomas. Herein, we observed a strong correlation between the expression of HMGA2 and PLAG1 in 14 benign and 23 malignant thyroid tumors. To address the question if PLAG1 can be activated by HMGA2, the expression of both genes was quantified in 32 uterine leiomyomas 17 of which exhibited an overexpression of HMGA2. All leiomyomas with HMGA2 overexpression also revealed an activation of PLAG1 in the absence of detectable chromosome 8 abnormalities affecting the PLAG1 locus. To further investigate if the overexpression of PLAG1 is inducible by HMGA2 alone, HMGA2 was transiently overexpressed in MCF-7 cells. An increased PLAG1 expression was observed 24 and 48 h after transfection. Likewise, stimulation of HMGA2 by FGF1 in adipose tissue-derived stem cells led to a simultaneous increase of PLAG1 mRNA. Altogether, these data suggest that HMGA2 is an upstream activator of PLAG1. Accordingly, this may explain the formation of tumors as similar as lipomas and lipoblastomas resulting from an activation of either of both genes by chromosomal rearrangements.

HMGA2 expression in white adipose tissue linking cellular senescence with diabetes.

There is a clear link between overweight, gain of white adipose tissue, and diabetes type 2 (T2D). The molecular mechanism of the gain of adipose tissue is linked with the expression of high mobility group protein AT-hook 2 (HMGA2), and recent studies revealed an association with a SNP near HMGA2. In this study, we investigated the gene expression of HMGA2, p14 (Arf) , CDKN1A, and BAX in human abdominal subcutaneous white adipose tissue from 157 patients. We found a significant higher HMGA2 expression in obese individuals than in non-obese patients. Furthermore, the HMGA2 expression in white adipose tissue in patient with type 2 diabetes was significantly higher than in nondiabetic patients. There is an association between the DNA-binding nonhistone protein HMGA2 and the risk of developing T2D that remains mechanistically unexplained so far. Likewise, p14(Arf), an inducer of cellular senescence, has been associated with the occurrence of T2D. The data of the present study provide evidence that both proteins act within the same network to drive proliferation of adipose tissue stem and precursor cells, senescence, and increased risk of T2D, respectively.

Molecular topography of the MED12-deleted region in smooth muscle tumors: a possible link between non-B DNA structures and hypermutability.

BACKGROUND: Deletions of the gene encoding mediator subcomplex 12 (MED12) in human smooth muscle tumors rank among the most frequent genomic alterations in human tumors at all. In a minority of these cases, small deletions are found. In an attempt to delineate key features of the deletions aimed at a better understanding of the molecular pathogenesis of uterine smooth muscle tumors we have analyzed 70 MED12 deletions including 46 cases from the literature and 24 own unpublished cases. RESULTS: The average length of the deletions was 18.7 bp ranging between 2 bp and 43 bp. While in general multitudes of 3 clearly dominated leaving the transcript in frame, deletions of 21, 24, 30, and 33 nucleotides were clearly underrepresented. Within the DNA segment affected deletion breakpoints were not randomly distributed. Most breakpoints clustered within the center of the segment where two peaks of breakpoint clusters could be distinguished. Interestingly, one of these clusters coincides with the loop of a putative folded non-B DNA structure whereas a much lower number of breaks noted in the 5' and 3' stem of the structure forming an intramolecular B-helix. The second cluster mainly consisting of 3' breaks was located in a region downstream adjacent to the stem. CONCLUSION: The present study describes for the first time main characteristics of MED12 deletions occurring in smooth muscle tumors. Interestingly, the non-random distribution of breakpoints within the deletion hotspot region may point to a role of non-canonical DNA structures for the occurrence of these mutations and the molecular pathogenesis of uterine smooth muscle tumors, respectively.

MED12 mutations occurring in benign and malignant mammalian smooth muscle tumors.

Mutations of the mediator subcomplex 12 gene (MED12) recently have been described in a large group of uterine leiomyomas (UL) but only in a single malignant uterine smooth muscle tumor. To further address the occurrence of fibroid-type MED12 mutations in smooth muscle tumors, we have analyzed samples from 34 leiomyosarcomas (LMS), 21 UL, two extrauterine leiomyomas (EL), and 10 canine genital leiomyomas for the presence of MED12 mutations of the UL-type. Interestingly, besides UL MED12 mutations were found in one uterine LMS, one EL, and two canine vaginal leiomyomas. The results confirm the occurrence of fibroid-type MED12 mutations in malignant uterine smooth muscle tumors thus suggesting a rare but existing leiomyoma-LMS sequence. In addition, for the first time MED12 mutations are reported in smooth muscle tumors in a non-primate mammalian species.

The expression of HMGA2 varies strongly among colon carcinomas.

BACKGROUND: The expression of high mobility group protein AT-hook2 (HMGA2) indicates a worse prognosis in many epithelial malignancies, such as colon cancer. The present study addresses methodological aspects, as well as the genetic background, of the HMGA2 expression in colon cancer. MATERIALS AND METHODS: Samples of 38 colon carcinomas were studied for the expression of HMGA2 by quantitative Real-Time PCR (qRT-PCR). In selected cases, immunohistochemistry (IHC) was also performed. RESULTS: The overexpression of HMGA2, compared to adjacent mucosa, is not consistent among colon carcinomas: Only a minority of carcinomas strongly overexpressed HMGA2, but in no more than 50% of the tumors did the expression exceed the average value in mucosa samples. qRT-PCR clearly reveals a continuum between cases with high and low expression. CONCLUSION: For HMGA2-based risk assessment, continuous rather than discontinuous models seem to be most appropriate. However, in daily practice, IHC seems to be a suitable method to stratify for high-risk patients.

MED12 mutations in uterine fibroids--their relationship to cytogenetic subgroups.

Recurrent chromosomal alterations are found in roughly 20% of all uterine fibroids but in the majority cytogenetic changes are lacking. Recently, mutations of the gene mediator subcomplex 12 (MED12) have been detected in a majority of fibroids but no information is available whether or not they co-occur with cytogenetic subtypes as, e.g., rearrangements of the genes encoding high mobility group AT-hook (HMGA) proteins. In a total of 80 cytogenetically characterized fibroids from 50 patients, we were not only able to confirm the frequent occurrence of MED12 mutations but also to stratify two mutually exclusive pathways of leiomyomagenesis with either rearrangements of HMGA2 reflected by clonal chromosome abnormalities affecting 12q14~15 or by mutations affecting exon 2 of MED12. On average the latter mutations were associated with a significantly smaller tumor size. However, G>A transitions of nucleotides c.130 or c.131 correlate with a significantly larger size of the fibroids compared to other MED12 mutations thus explaining the high prevalence of the former mutations among clinically detectable fibroids. Interestingly, fibroids with MED12 mutations expressed significantly higher levels of the gene encoding wingless-type MMTV integration site family, member 4 (WNT4). Based on these findings and data from the literature, we hypothesize that estrogen and the mutated MED12 cooperate in activating the Wnt pathway which in turn activates ß-catenin known to cause leiomyoma-like lesions in a mouse model. The occurrence of a "fibroid-type mutation" in a rare histologic subtype of endometrial polyps suggests that this mechanism is not confined to uterine leiomyomas.

BMP4 increases expression of HMGA2 in mesenchymal stem cells.

BMP4 has been linked to early steps of adipocyte lineage differentiation but only little is known about its corresponding downstream pathways. Herein, we have investigated whether or not the expression of high mobility group protein HMGA2, another protein linked to proliferation and differentiation within the process of adipogenesis, may be influenced by BMP4 signaling in adipose tissue derived stem cells. Compared to FGF1, a strong inducer of HMGA2 in immortalized pre-adipocytes, BMP4 was found moderately to induce the HMGA2 mRNA expression in serum starved adipose tissue derived stem cells and myometrial cells. In contrast, no such activity was noted in canine bone marrow derived mesenchymal stem cells. As to adipocyte lineage differentiation the functions of BMP4 and HMGA2 mechanistically overlap. Thus, we propose that in adipose tissue BMP4 acts in part by activating HMGA2 making this architectural transcription factor one of the major downstream players in that system.

HMGA2 and p14Arf: major roles in cellular senescence of fibroids and therapeutic implications.

AIM: To address the influence of genes involved in stem cell self-renewal and senescence on the growth of leiomyoma cells in vitro and to explore possible therapeutic implications of a targeted disruption of the p53-murine double minute 2 (MDM2) interaction. MATERIALS AND METHODS: Gene expression studies (qRT-PCR) of fibroid tissue and cells; ß-galactosidase stain and qRT-PCR after antagonizing MDM2. RESULTS: In fibroid cells, expression of HMGA2 decreased with passaging while that of p14(Arf) increased. Expression of these markers significantly positively, and negatively, respectively, influenced proliferation. Administration of nutlin-3, an MDM2 antagonist, induced cellular senescence and increased the expression of BAX. This, along with a significant correlation between p14(Arf) and BAX expression in native fibroids, suggests that p14(Arf) triggers senescence as well as apoptosis. CONCLUSION: p14(Arf) and HMGA2 seem to play a pivotal role in controlling the growth of fibroid cells. Antagonizing MDM2 induces senescence, as well as apoptosis, and may offer a chance to treat fibroids.

p14Arf acts as an antagonist of HMGA2 in senescence of mesenchymal stem cells-implications for benign tumorigenesis.

HMGA2 is a major regulator of benign tumorigenesis from mesenchyme-derived tissues and stem-cell self-renewal. It has been postulated that HMGA2 mediates its critical function by decreasing p16(Ink4a)/p14(Arf) expression and cellular senescence. To repress the oncogenic activity of HMGA2, the lin-28-let-7 axis is thought to increasingly repress the expression of HMGA2 with age. To understand the HMGA2-p14(Arf) -relationship in benign tumorigenesis, we performed a series of experiments on mesenchymal stem-cells, i.e., the proposed cells of origin of lipomas and uterine leiomyomas. The expression of both genes was inversely correlated during senescence in vitro but contrary to the expectations in adipose tissue derived stem cells (ADSCs) stimulation of HMGA2 by FGF1 increased the expression of p14(Arf) . Based on the assumption that in ADSCs p14(Arf) is repressing HMGA2, siRNA silencing of p14(Arf) was performed resulting in a significant upregulation of HMGA2. To see if p14(Arf) can repress HMGA2 by a TP53-dependent mechanism, nutlin-3, a known MDM2 antagonist, was used which not only increased the activity of the senescence, associated markers p21 and beta-galactosidase, but also decreased the expression of HMGA2, suggesting that p14(Arf) indeed influences HMGA2 by a p53-dependent mechanism because nutlin-3 stabilizes p53. Accordingly, the HMGA2 response triggered by serum was reduced by treatment of ADSCs with nutlin-3. As to the interaction between HMGA2 and p14(Arf) in benign tumorigenesis, we propose a model where akin to MSC self-renewal during tissue repair the simultaneous increase of p14(Arf) with HMGA2 ensures genomic stability, whereas in turn p14(Arf) can repress HMGA2 via TP53.

HMGA proteins regulate the expression of FGF2 in uterine fibroids.

In human fibroids genes encoding the high-mobility proteins containing the 'AT-hook' DNA-binding motif (HMGA) are frequently affected by non-random chromosomal rearrangements. Thus, the different proteins and their derivatives resulting from these genomic rearrangements can be assumed to be involved in the genesis of these tumors by activation of largely identical downstream pathways. Constructs encoding HMGA proteins and their relevant derivatives were overexpressed in human myometrial cells, and RNA isolated from these cells was hybridized to filter arrays. Four genes were either up- or down-regulated at least 2-fold after overexpression of either of the HMGA genes and their derivatives. FGF2 (fibroblast growth factor 2) was one of these genes, and we were then able to show by microarray analyses that tumors with rearrangements of the HMGA2 locus (n = 8) expressed significantly higher levels of FGF2 than those with an apparently normal karyotype (n = 47). Accordingly, by quantitative real-time PCR uterine leiomyomas with rearrangements of the HMGA2 locus were found to express significantly higher levels of FGF2 than those with an apparently normal karyotype with a linear relationship between the expression of FGF2 and the level of HMGA2 overexpression as well as the tumor size. The results of western blot analyses confirmed these findings. Moreover, stimulation of myometrial tissue by FGF1, a strong inducer of HMGA2, leads to an increase of HMGA2 as well as FGF2 expression. In conclusion, the results contribute to the understanding of the association between the overexpression of HMGA proteins, the regulation of FGF2 expression and the size of fibroids.

Cell culture and senescence in uterine fibroids.

The in vitro growth of cells from uterine fibroids is characterized by an early onset of senescence. Often, an even lower growth potential than that of matching myometrial cells is noted. Also, the tremendous differences in the expression of the high mobility group protein HMGA2 seen when comparing fibroids of different genetic subtypes are surprisingly not reflected by significant differences in their growth potential in vitro. We aimed to evaluate possible changes of the HMGA2 expression level between the native tissue and cell cultures, so we performed quantitative real-time polymerase chain reaction studies that revealed a marked decrease of the HMGA2 mRNA in culture in those cases with overexpression of HMGA2. In the two cases initially showing the highest expression, it decreased by approximately 97%. Associated with the decrease of HMGA2 was a clearly increased expression of the senescence-associated p19(Arf). Together, these findings explain the similar behavior of cell cultures from fibroids of different genetic subgroups and may also offer an explanation for the early onset of in vitro senescence in these cell cultures.

HMGA2 and the p19Arf-TP53-CDKN1A axis: a delicate balance in the growth of uterine leiomyomas.

Pathogenetically, uterine leiomyomas (ULs) can be interpreted as the result of a monoclonal abnormal proliferation of myometrial cells. Oncogene-induced senescence (OIS) is a frequent phenomenon in premalignant lesions that leads to a growth arrest mainly by the activation of two potent growth-inhibitory pathways as represented by p16(Ink4a) and p19(Arf). The relevance of OIS for the development of UL has not been addressed, but HMGA2, encoded by a major target gene of recurrent chromosomal abnormalities in UL, has been implicated in the repression of the Ink4a/Arf (CDKN2A) locus. This prompted us to examine if HMGA2 contributes to the growth of leiomyomas by repressing this locus. Contrary to the expectations, we were able to show that generally ULs express significantly higher levels of p19(Arf) mRNA than myometrium and that UL with 12q14 approximately 15 rearrangements showed higher expression levels than UL with other cytogenetic aberrations. Furthermore, the finding of a significant correlation between the expressions of p19(Arf) and CDKN1A shows that p19(Arf) triggers senescence rather than apoptosis in UL. Furthermore, the expression levels of HMGA2, p19(Arf), and CDKN1A were found to be correlated with the size of the tumors, indicating that an enhanced growth potential is counterbalanced by the p19(Arf) pathway. Mechanistically, the UL may thus execute a program already present in their cell of origin, where it is activated to protect the genome, for example, in the case of enhanced proliferation. In summary, the results identify the p19(Arf)-TP53-CDKN1A pathway as a major player in the growth control and genomic stability of uterine fibroids.