Down's syndrome protects against breast cancer: is a constitutional cell microenvironment the key?

Choroid plexus defects in Down syndrome brain organoids enhance neurotropism of SARS-CoV-2

Why individuals with Down syndrome (DS) are more susceptible to SARS-CoV-2-induced neuropathology remains elusive. Choroid plexus (ChP) plays critical roles in barrier function and immune response modulation and expresses the ACE2 receptor and the chromosome 21-encoded TMPRSS2 protease, suggesting its substantial role in establishing SARS-CoV-2 infection in the brain. To explore this, we established brain organoids from DS and isogenic euploid iPSC that consist of a core of functional cortical neurons surrounded by a functional ChP-like epithelium (ChPCOs). DS-ChPCOs recapitulated abnormal DS cortical development and revealed defects in ciliogenesis and epithelial cell polarity in ChP-like epithelium. We then demonstrated that the ChP-like epithelium facilitates infection and replication of SARS-CoV-2 in cortical neurons and that this is increased in DS. Inhibiting TMPRSS2 and furin activity reduced viral replication in DS-ChPCOs to euploid levels. This model enables dissection of the role of ChP in neurotropic virus infection and euploid forebrain development and permits screening of therapeutics for SARS-CoV-2-induced neuropathogenesis.

Ten Reasons Why People With Down Syndrome are Protected From the Development of Most Solid Tumors -A Review

People with Down syndrome have unique characteristics as a result of the presence of an extra chromosome 21. Regarding cancer, they present a unique pattern of tumors, which has not been fully explained to date. Globally, people with Down syndrome have a similar lifetime risk of developing cancer compared to the general population. However, they have a very increased risk of developing certain tumors (e.g., acute leukemia, germ cell tumors, testicular tumors and retinoblastoma) and, on the contrary, there are some other tumors which appear only exceptionally in this syndrome (e.g., breast cancer, prostate cancer, medulloblastoma, neuroblastoma and Wilms tumor). Various hypotheses have been developed to explain this situation. The genetic imbalance secondary to the presence of an extra chromosome 21 has molecular consequences at several levels, not only in chromosome 21 but also throughout the genome. In this review, we discuss the different proposed mechanisms that protect individuals with trisomy 21 from developing solid tumors: genetic dosage effect, tumor suppressor genes overexpression, disturbed metabolism, impaired neurogenesis and angiogenesis, increased apoptosis, immune system dysregulation, epigenetic aberrations and the effect of different microRNAs, among others. More research into the molecular pathways involved in this unique pattern of malignancies is still needed.

iPSC-derived progenitor stromal cells provide new insights into aberrant musculoskeletal development and resistance to cancer in down syndrome

Down syndrome (DS) is a congenital disorder caused by trisomy 21 (T21). It is associated with cognitive impairment, muscle hypotonia, heart defects, and other clinical anomalies. At the same time, individuals with Down syndrome have lower prevalence of solid tumor formation. To gain new insights into aberrant DS development during early stages of mesoderm formation and its possible connection to lower solid tumor prevalence, we developed the first model of two types of DS iPSC-derived stromal cells. Utilizing bioinformatic and functional analyses, we identified over 100 genes with coordinated expression among mesodermal and endothelial cell types. The most significantly down-regulated processes in DS mesodermal progenitors were associated with decreased stromal progenitor performance related to connective tissue organization as well as muscle development and functionality. The differentially expressed genes included cytoskeleton-related genes (actin and myosin), ECM genes (Collagens, Galectin-1, Fibronectin, Heparan Sulfate, LOX, FAK1), cell cycle genes (USP16, S1P complexes), and DNA damage repair genes. For DS endothelial cells, our analysis revealed most down-regulated genes associated with cellular response to external stimuli, cell migration, and immune response (inflammation-based). Together with functional assays, these results suggest an impairment in mesodermal development capacity during early stages, which likely translates into connective tissue impairment in DS patients. We further determined that, despite differences in functional processes and characteristics, a significant number of differentially regulated genes involved in tumorigenesis were expressed in a highly coordinated manner across endothelial and mesodermal cells. These findings strongly suggest that microRNAs (miR-24-4, miR-21), cytoskeleton remodeling, response to stimuli, and inflammation can impact resistance to tumorigenesis in DS patients. Furthermore, we also show that endothelial cell functionality is impaired, and when combined with angiogenic inhibition, it can provide another mechanism for decreased solid tumor development. We propose that the same processes, which specify the basis of connective tissue impairment observed in DS patients, potentially impart a resistance to cancer by hindering tumor progression and metastasis. We further establish that cancer-related genes on Chromosome 21 are up-regulated, while genome-wide cancer-related genes are down-regulated. These results suggest that trisomy 21 induces a modified regulation and compensation of many biochemical pathways across the genome. Such downstream interactions may contribute toward promoting tumor resistant mechanisms.

Human iPSC-derived Down syndrome astrocytes display genome-wide perturbations in gene expression, an altered adhesion profile, and increased cellular dynamics

Down syndrome (DS), caused by the triplication of human chromosome 21, leads to significant alterations in brain development and is a major genetic cause of intellectual disability. While much is known about changes to neurons in DS, the effects of trisomy 21 on non-neuronal cells such as astrocytes are poorly understood. Astrocytes are critical for brain development and function, and their alteration may contribute to DS pathophysiology. To better understand the impact of trisomy 21 on astrocytes, we performed RNA-sequencing on astrocytes from newly produced DS human induced pluripotent stem cells (hiPSCs). While chromosome 21 genes were upregulated in DS astrocytes, we found consistent up- and down-regulation of genes across the genome with a strong dysregulation of neurodevelopmental, cell adhesion and extracellular matrix molecules. ATAC (assay for transposase-accessible chromatin)-seq also revealed a global alteration in chromatin state in DS astrocytes, showing modified chromatin accessibility at promoters of cell adhesion and extracellular matrix genes. Along with these transcriptomic and epigenomic changes, DS astrocytes displayed perturbations in cell size and cell spreading as well as modifications to cell-cell and cell-substrate recognition/adhesion, and increases in cellular motility and dynamics. Thus, triplication of chromosome 21 is associated with genome-wide transcriptional, epigenomic and functional alterations in astrocytes that may contribute to altered brain development and function in DS.

[Trisomy 21 and cancers]

Patients with trisomy 21, still called Down's syndrome (DS), present a particular tumoral profile compared to the general population with an increased incidence of leukaemia in the childhood and a low risk of solid cancer in the adulthood. DS children indeed present a 50-fold risk of developing a leukaemia compared to age-matched non-trisomic children and most of them develop a specific myelodysplasic disorder called transient myelodysplasic disorder. In spite of the low incidence of solid tumors, some are very rare as breast cancer, nephroblastoma, neuroblastoma and medulloblastoma, whereas the others remain more frequent as retinoblastoma, lymphoma and gonadal and extragonadal germ cell tumours. In this review, we present possible mechanisms which can favour, or on the contrary repress the formation and progression of tumours in DS patients, which are related to gene effect dosage of oncogenes or tumour repressors on chromosome 21, tumour angiogenesis, apoptosis and epithelial cell-stroma interactions.

Stromal deletion of the APC tumor suppressor in mice triggers development of endometrial cancer

The contribution of the stromal microenvironment to the progression of endometrial cancer has not been well explored. We have conditionally expressed a mutant allele of adenomatous polyposis coli (APC(cKO)) in murine uterine stroma cells to study its effect on uterine development and function. In addition to metrorrhagia, the mice develop complex atypical endometrial gland hyperplasia that progresses to endometrial carcinoma in situ and endometrial adenocarcinoma as evidenced by myometrial invasion. Stromal cells subjacent to the carcinoma cells express alpha-smooth muscle actin (αSMA) with fewer cells expressing platelet-derived growth factor α compared with normal stromal cells, suggesting that the mutant stromal cells have acquired a more myofibroblastic phenotype, which have been described as cancer-associated fibroblasts and have been shown to induce carcinogenesis in other organ systems. Analyses of human endometrial cancer specimens showed substantial αSMA expression in the stroma compared with normal endometrial stroma cells. We also show that APC(cKO) mutant uteri and human endometrial cancer have decreased stromal levels of transforming growth factor β and bone morphogenetic protein activities and that the mutant uteri failed to respond to exogenous estradiol stimulation. The mutant stroma cells also had higher levels of vascular endothelial growth factor and stromal derived factor signaling components and diminished expression of estrogen receptor α and progesterone receptor, which is common in advanced stages of human endometrial cancer and is an indicator of poor prognosis. Our results indicate that de novo mutation or loss of heterozygosity in stromal APC is sufficient to induce endometrial hyperplasia and endometrial carcinogenesis by mechanisms that are consistent with unopposed estrogen signaling in the endometrial epithelium.

Trisomy-21 gene dosage over-expression of miRNAs results in the haploinsufficiency of specific target proteins

Down syndrome (DS) or Trisomy 21 (Ts21) is caused by the presence of an extra copy of all or part of human chromosome 21 (Hsa21) and is the most frequent survivable congenital chromosomal abnormality. Bioinformatic annotation has established that Hsa21 harbors more than 400 genes, including five microRNA (miRNA) genes (miR-99a, let-7c, miR-125b-2, miR-155, and miR-802). MiRNAs are endogenous, single-stranded, small non-coding RNA molecules that regulate gene expression by interacting with specific recognition elements harbored within the 3'-untranslated region (3'-UTR) of mRNAs and subsequently target these mRNAs for translational repression or destabilization. MiRNA expression profiling, miRNA RT-PCR, and miRNA in situ hybridization experiments have demonstrated that Hsa21-derived miRNAs were over-expressed in fetal brain and heart specimens isolated from individuals with DS. We now propose that Ts21 gene dosage over-expression of Hsa21-derived miRNAs in DS individuals result in the decreased expression of specific target proteins (i.e. haploinsufficiency) that contribute, in part, to the DS phenotype.

New concepts in breast cancer emerge from analyzing clinical data using numerical algorithms

A small international group has recently challenged fundamental concepts in breast cancer. As a guiding principle in therapy, it has long been assumed that breast cancer growth is continuous. However, this group suggests tumor growth commonly includes extended periods of quasi-stable dormancy. Furthermore, surgery to remove the primary tumor often awakens distant dormant micrometastases. Accordingly, over half of all relapses in breast cancer are accelerated in this manner. This paper describes how a numerical algorithm was used to come to these conclusions. Based on these findings, a dormancy preservation therapy is proposed.

Hypothesis: primary antiangiogenic method proposed to treat early stage breast cancer

BACKGROUND

Women with Down syndrome very rarely develop breast cancer even though they now live to an age when it normally occurs. This may be related to the fact that Down syndrome persons have an additional copy of chromosome 21 where the gene that codes for the antiangiogenic protein Endostatin is located. Can this information lead to a primary antiangiogenic therapy for early stage breast cancer that indefinitely prolongs remission? A key question that arises is when is the initial angiogenic switch thrown in micrometastases? We have conjectured that avascular micrometastases are dormant and relatively stable if undisturbed but that for some patients angiogenesis is precipitated by surgery. We also proposed that angiogenesis of micrometastases very rarely occurs before surgical removal of the primary tumor. If that is so, it seems possible that we could suggest a primary antiangiogenic therapy but the problem then arises that starting a therapy before surgery would interfere with wound healing.

RESULTS

The therapy must be initiated at least one day prior to surgical removal of the primary tumor and kept at a Down syndrome level perhaps indefinitely. That means the drug must have virtually no toxicity and not interfere meaningfully with wound healing. This specifically excludes drugs that significantly inhibit the VEGF pathway since that is important for wound healing and because these agents have some toxicity. Endostatin is apparently non-toxic and does not significantly interfere with wound healing since Down syndrome patients have no abnormal wound healing problems.

CONCLUSION

We propose a therapy for early stage breast cancer consisting of Endostatin at or above Down syndrome levels starting at least one day before surgery and continuing at that level. This should prevent micrometastatic angiogenesis resulting from surgery or at any time later. Adjuvant chemotherapy or hormone therapy should not be necessary. This can be continued indefinitely since there is no acquired resistance that develops, as happens in most cancer therapies.

Loss of singleminded-2s in the mouse mammary gland induces an epithelial-mesenchymal transition associated with up-regulation of slug and matrix metalloprotease 2

The short splice variant of the basic helix-loop-helix Per-Arnt-Sim transcription factor Singleminded-2, SIM2s, has been implicated in development and is frequently lost or reduced in primary breast tumors. Here, we show that loss of Sim2s causes aberrant mouse mammary gland ductal development with features suggestive of malignant transformation, including increased proliferation, loss of polarity, down-regulation of E-cadherin, and invasion of the surrounding stroma. Additionally, knockdown of SIM2s in MCF-7 breast cancer cells contributed to an epithelial-mesenchymal transition (EMT) and increased tumorigenesis. In both Sim2(-/-) mammary glands and SIM2s-depleted MCF7 cells, these changes were associated with increased SLUG and MMP2 levels. SIM2s protein was detectable on the SLUG promoter, and overexpression of SIM2s repressed expression from a SLUG-controlled reporter in a dose-dependent manner. To our knowledge, SIM2s is the first protein shown to bind and repress the SLUG promoter, providing a plausible explanation for the development role and breast tumor-suppressive activity of SIM2s. Together, our results suggest that SIM2s is a key regulator of mammary-ductal development and that loss of SIM2s expression is associated with an invasive, EMT-like phenotype.

Paradoxes in carcinogenesis: new opportunities for research directions

Background

The prevailing paradigm in cancer research is the somatic mutation theory that posits that cancer begins with a single mutation in a somatic cell followed by successive mutations. Much cancer research involves refining the somatic mutation theory with an ever increasing catalog of genetic changes. The problem is that such research may miss paradoxical aspects of carcinogenesis for which there is no likely explanation under the somatic mutation theory. These paradoxical aspects offer opportunities for new research directions that should not be ignored.

Discussion

Various paradoxes related to the somatic mutation theory of carcinogenesis are discussed: (1) the presence of large numbers of spatially distinct precancerous lesions at the onset of promotion, (2) the large number of genetic instabilities found in hyperplastic polyps not considered cancer, (3) spontaneous regression, (4) higher incidence of cancer in patients with xeroderma pigmentosa but not in patients with other comparable defects in DNA repair, (5) lower incidence of many cancers except leukemia and testicular cancer in patients with Down's syndrome, (6) cancer developing after normal tissue is transplanted to other parts of the body or next to stroma previously exposed to carcinogens, (7) the lack of tumors when epithelial cells exposed to a carcinogen were transplanted next to normal stroma, (8) the development of cancers when Millipore filters of various pore sizes were was inserted under the skin of rats, but only if the holes were sufficiently small. For the latter paradox, a microarray experiment is proposed to try to better understand the phenomena.

Summary

The famous physicist Niels Bohr said "How wonderful that we have met with a paradox. Now we have some hope of making progress." The same viewpoint should apply to cancer research. It is easy to ignore this piece of wisdom about the means to advance knowledge, but we do so at our peril.

The profile and incidence of cancer in Down syndrome

BACKGROUND

Down syndrome is one of the commonest causes of intellectual disability. As life expectancy improves with early and more intensive surgical and medical treatments, people with the disorder are more likely to exhibit classic morbidity and mortality patterns and be diagnosed with diseases such as cancer.

METHODS

A profile of cancer cases among people with Down syndrome has been compiled, based on the analysis of a linked data set that included information from the Disability Services Commission of Western Australian and the State Cancer Registry.

RESULTS AND CONCLUSIONS

Although the total age- and sex-standardized incidence ratios (SIRs) for people with Down syndrome were similar to that for the general population, SIRs for leukaemia were significantly higher while the incidence of certain other types of cancers was reduced. Overall, there was a lower incidence of solid tumours in Down syndrome, possibly reflecting the age profile of the study cohort.

Aspects of digestive tract tumors in Down syndrome: a literature review

The purpose of this study was to describe the digestive neoplasms found in persons with Down syndrome. Due to intellectual disability, persons with Down syndrome do not convey their symptoms and pain, leading to delayed diagnosis and potentially worse outcome. It is thus important to know which organs are at risk for tumors and possible tumor risk factors. In a review of the literature, we found 13 benign tumors and 127 cancers in 1 fetus, 8 children, and 131 adults with Down syndrome. The review suggests a decreased incidence of digestive cancer, however, with a possible increased incidence of neoplasms of the pancreas and gallbladder. The distribution of cancers is distinct from that in the general population and that in persons with other intellectual disabilities who share the same life conditions, suggesting that constitutional protective factors exist. This review may allow a more specific, adapted medical follow-up for persons with Down syndrome and could help to elucidate the oncogenesis of digestive neoplasms.