Acquisition of a second mutation of the Tp53 alleles immediately precedes epithelial morphological transformation in ovarian tumorigenicity

The fallopian tube, "precursor escape" and narrowing the knowledge gap to the origins of high-grade serous carcinoma

Most ovarian carcinomas are high-grade serous carcinomas (HGSC) that contain TP53 mutations, present at advanced stage, and eventually become resistant to chemotherapy. The rapid evolution of this disease has been attributed to an origin in the distal fallopian tube, in the form of serous tubal intraepithelial carcinomas (STICs). This has led to a disease model where malignancy develops first in the tube and spreads to the peritoneum or regional lymph nodes. However, although most early or incidentally discovered HGSCs manifest in the tube with STICs, many advanced HGSCs are not accompanied by a malignancy in the fimbria. To resolve this paradox, the focus has shifted to earlier, premalignant serous proliferations (ESPs) in the tubes, which lack the cytomorphologic features of malignancy but contain TP53 mutations. These have been termed p53 signatures or serous tubal intraepithelial lesions (STILs). Although they have not been presumed to have cancer-causing potential by themselves, some ESPs have recently been shown to share identical TP53 mutations with concurrent HGSCs, indicating a shared lineage between these early mucosal changes and metastatic malignancy. This discovery supports a paradigm by which HGSCs can emerge not only from STICs but also from exfoliated precursor cells (precursor escape) that eventually undergo malignant transformation within the peritoneal cavity. This paradigm unifies both localized and widespread HGSCs to a visible pre-existing cellular alteration in the tubal epithelium, and highlights a consistent and necessary biologic event (TP53 mutation) rarely encountered in the ovary or secondary Mullerian system. This dual pathway to HGSCs underscores the subtle nature of many serous cancer origins in the tube, explains contrasting clinico-pathologic presentations, and explains why, until recently, the fallopian tube was unappreciated as the principal origin of HGSCs. Moreover, it highlights additional challenges faced in preventing or intercepting HGSCs at a curable stage.

Molecular analysis of high-grade serous ovarian carcinoma with and without associated serous tubal intra-epithelial carcinoma

Many high-grade serous carcinomas (HGSCs) of the pelvis are thought to originate in the distal portion of the fallopian tube. Serous tubal intra-epithelial carcinoma (STIC) lesions are the putative precursor to HGSC and identifiable in ~ 50% of advanced stage cases. To better understand the molecular etiology of HGSCs, we report a multi-center integrated genomic analysis of advanced stage tumors with and without STIC lesions and normal tissues. The most significant focal DNA SCNAs were shared between cases with and without STIC lesions. The RNA sequence and the miRNA data did not identify any clear separation between cases with and without STIC lesions. HGSCs had molecular profiles more similar to normal fallopian tube epithelium than ovarian surface epithelium or peritoneum. The data suggest that the molecular features of HGSCs with and without associated STIC lesions are mostly shared, indicating a common biologic origin, likely to be the distal fallopian tube among all cases.High-grade serous carcinomas (HGSCs) are associated with precursor lesions (STICs) in the fallopian epithelium in only half of the cases. Here the authors report the molecular analysis of HGSCs with and without associated STICs and show similar profiles supporting a common origin for all HGSCs.

Progression inference for somatic mutations in cancer

Computational methods were employed to determine progression inference of genomic alterations in commonly occurring cancers. Using cross-sectional TCGA data, we computed evolutionary trajectories involving selectivity relationships among pairs of gene-specific genomic alterations such as somatic mutations, deletions, amplifications, downregulation, and upregulation among the top 20 driver genes associated with each cancer. Results indicate that the majority of hierarchies involved TP53, PIK3CA, ERBB2, APC, KRAS, EGFR, IDH1, VHL, etc. Research into the order and accumulation of genomic alterations among cancer driver genes will ever-increase as the costs of nextgen sequencing subside, and personalized/precision medicine incorporates whole-genome scans into the diagnosis and treatment of cancer.

Identifying a highly-aggressive DCIS subgroup by studying intra-individual DCIS heterogeneity among invasive breast cancer patients

The heterogeneity among multiple ductal carcinoma in situ (DCIS) lesions within the same patient also diagnosed with invasive ductal carcinoma (IDC) has not been well evaluated, leaving research implications of intra-individual DCIS heterogeneity yet to be explored. In this study formalin-fixed paraffin embedded sections from 36 patients concurrently diagnosed with DCIS and IDC were evaluated by immunohistochemistry. Ten DCIS lesions from each patient were then randomly selected and scored. Our results showed that expression of PR, HER2, Ki-67, and p16 varied significantly within DCIS lesions from a single patient (P<0.05 for PR; P<1×10⁻⁸ for HER2, Ki-67 and p16). In addition, seventy-two percent of the individuals had heterogeneous expression of at least 2/6 markers. Importantly, by evaluating the expression of promising DCIS risk biomarkers (Ki-67, p53 and p16) among different DCIS subgroups classified by comparing DCIS molecular subtypes with those of adjacent normal terminal duct lobular units (TDLU) and IDC, our results suggest the existence of a highly-aggressive DCIS subgroup, which had the same molecular subtype as the adjacent IDC but not the same subtype as the adjacent normal TDLU. By using a systematic approach, our results clearly demonstrate that intra-individual heterogeneity in DCIS is very common in patients concurrently diagnosed with IDC. Our novel findings of a DCIS subpopulation with aggressive characteristics will provide a new paradigm for mechanistic studies of breast tumor progression and also have broad implications for prevention research as heterogeneous pre-invasive lesions are present in many other cancer types.

Abcc10 status affects mammary tumour growth, metastasis, and docetaxel treatment response

Background:

Resistance to chemotherapeutic agents is a major obstacle to cancer treatment. A group of ABC efflux pumps, the Multidrug Resistance Proteins, is a source of resistance. Herein, we investigated the role of ABCC10 in mammary tumours, given the important role we have defined for ABCC10 in transporting taxanes, and the recognition that some ABCC proteins have roles in tumour growth.

Methods:

ABCC10 expression was correlated to human breast cancer subtype using breast tissue microarrays. Real-time quantitative PCR and western blot analysis were used to examine ABCC10 expression in human breast cancer lines. Abcc10^−/− mice were crossed to MMTV-PyVmT mice to produce Abcc10^−/−vs Abcc10^+/+ mammary tumours and derivative cell lines. We used allograft and cellular assays to perform baseline and drug sensitization analysis of tumours and cell lines.

Results:

Clinical sample analyses indicated that ABCC10 was more highly expressed in Her2+ and ER+ than in Her2−, ER−, and triple-negative breast cancer. Unexpectedly, PyVmT; Abcc10^−/− tumours grew more rapidly than PyVmT; Abcc10^+/+ tumours and were associated with significantly reduced apoptosis and metastasis. PyVmT; Abcc10^−/− lines were less migratory than PyVmT; Abcc10^+/+ lines. Finally, we showed increased survival of docetaxel-treated MMTV-PyVmT; Abcc10^−/− mice compared with wild-type mice.

Conclusions:

These data identify roles for Abcc10 in breast cancer pathogenesis and in vivo docetaxel resistance.

Development of a mouse model of menopausal ovarian cancer

Despite significant understanding of the genetic mutations involved in ovarian epithelial cancer and advances in genomic approaches for expression and mutation profiling of tumor tissues, several key questions in ovarian cancer biology remain enigmatic: the mechanism for the well-established impact of reproductive factors on ovarian cancer risk remains obscure; cell of origin of ovarian cancer continue to be debated; and the precursor lesion, sequence, or events in progression remain to be defined. Suitable mouse models should complement the analysis of human tumor tissues and may provide clues to these questions currently perplexing ovarian cancer biology. A potentially useful model is the germ cell-deficient Wv (white spotting variant) mutant mouse line, which may be used to study the impact of menopausal physiology on the increased risk of ovarian cancer. The Wv mice harbor a point mutation in c-Kit that reduces the receptor tyrosine kinase activity to about 1–5% (it is not a null mutation). Homozygous Wv mutant females have a reduced ovarian germ cell reservoir at birth and the follicles are rapidly depleted upon reaching reproductive maturity, but other biological phenotypes are minimal and the mice have a normal life span. The loss of ovarian function precipitates changes in hormonal and metabolic activity that model features of menopause in humans. As a consequence of follicle depletion, the Wv ovaries develop ovarian tubular adenomas, a benign epithelial tumor corresponding to surface epithelial invaginations and papillomatosis that mark human ovarian aging. Ongoing work will test the possibility of converting the benign epithelial tubular adenomas into neoplastic tumors by addition of an oncogenic mutation, such as of Tp53, to model the genotype and biology of serous ovarian cancer. Model based on the Wv mice may have the potential to gain biological and etiological insights into ovarian cancer development and prevention.

Through the glass darkly: intraepithelial neoplasia, top-down differentiation, and the road to ovarian cancer

It is currently hoped that deaths from extra-uterine high-grade serous cancer (HGSC) will be reduced via opportunistic salpingectomy in healthy women. Accumulated data implicate the fimbria as a site of origin and descriptive molecular pathology and experimental evidence strongly support a serous carcinogenic sequence in the Fallopian tube. Both direct and indirect ('surrogate') precursors suggest that the benign tube undergoes important biological changes after menopause, acquiring abnormalities in gene expression that are often shared with malignancy, including PAX2, ALDH1, LEF1, RCN1, RUNX2, beta-catenin, EZH2, and others. However, the tube can be linked to only some HGSCs, recharging arguments that nearby peritoneum/ovarian surface epithelium (POSE) also hosts progenitors to this malignancy. A major sticking point is the difference in immunophenotype between POSE and Müllerian epithelium, essentially requiring mesothelial to Müllerian differentiation prior to or during malignant transformation to HGSC. However, emerging evidence implicates an embryonic or progenitor phenotype in the adult female genital tract with the capacity to differentiate, normally or during neoplastic transformation. Recently, a putative cell of origin for cervical cancer has been identified in the squamo-columnar (SC) junction, projecting a model whereby Krt7+ embryonic progenitors give rise to immunophenotypically distinct progeny under stromal influences via 'top down' differentiation. Similar differentiation can be seen in the endometrium with a parallel in juxtaposed mesothelial and Müllerian differentiation in the ovary. Abrupt mesothelial-Müllerian transitions remain to be proven, but would explain the rapid evolution, short asymptomatic interval, and absence of a defined epithelial starting point in many HGSCs. Resolving this question will require accurately distinguishing progenitor from progeny tumour cells in HGSC and pinpointing where initial transformation and trans-differentiation occur, whether in the tube or POSE. Both will be critical to expectations from prophylactic salpingectomy and future approaches to pelvic serous cancer prevention.

Poor survival with wild-type TP53 ovarian cancer?

OBJECTIVE

The objective of this study is to investigate whether wild-type TP53 status in high-grade serous ovarian carcinoma is associated with poorer survival.

METHODS

Clinical and genomic data of 316 sequenced samples from The Cancer Genome Atlas (TCGA) ovarian high-grade serous carcinoma study were downloaded from TCGA data portal. Association between wild-type TP53 and survival was analyzed with Kaplan Meier method and Cox regression. The diagnosis of high-grade serous carcinomas was evaluated by reviewing pathological reports and high-resolution hematoxylin and eosin (H&E) images from frozen sections. The authenticity of wild-type TP53 in these tumor samples was assessed by analyzing SNP array data with ASCAT algorithm, reverse phase protein array (RPPA) data and RNAseq data.

RESULTS

Fifteen patients with high grade serous ovarian carcinomas were identified to have wild-type TP53, which had significantly shorter survival and higher chemoresistance than those with mutated TP53. The authenticity of wild-type TP53 status in these fifteen patients was supported by SNP array, RPPA, and RNAseq data. Except four cases with mixed histology, the classification as high grade serous carcinomas was supported by pathological reports and H&E images. Using RNAseq data, it was found that EDA2R gene, a direct target of wild-type TP53, was highly up-regulated in samples with wild-type TP53 in comparison to samples with either nonsense or missense TP53 mutations.

CONCLUSION

Although patients with wild-type TP53 ovarian cancer were rare in the TCGA high grade ovarian serous carcinomas cohort, these patients appeared to have a poorer survival and were more chemoresistant than those with mutated TP53. Differentially expressed genes in these TP53 wild-type tumors may provide insight in the molecular mechanism in chemotherapy resistance.

Ovarian Cancer Is an Imported Disease: Fact or Fiction?

The cell of origin of ovarian cancer has been long debated. The current paradigm is that epithelial ovarian cancer (EOC) arises from the ovarian surface epithelium (OSE). OSE is composed of flat, nondescript cells more closely resembling the mesothelium lining the peritoneal cavity, with which it is continuous, rather than the various histologic types of ovarian carcinoma (serous, endometrioid, and clear cell carcinoma), which have a Müllerian phenotype. Accordingly, it has been argued that the OSE undergoes a process termed "metaplasia" to account for this profound morphologic transformation. Recent molecular and clinicopathologic studies not only have failed to support this hypothesis but also have provided evidence that EOC stems from Müllerian-derived extraovarian cells that involve the ovary secondarily, thereby calling into question the very existence of primary EOC. This new model of ovarian carcinogenesis proposes that fallopian tube epithelium (benign or malignant) implants on the ovary to give rise to both high-grade and low-grade serous carcinomas, and that endometrial tissue implants on the ovary and produces endometriosis, which can undergo malignant transformation into endometrioid and clear cell carcinoma. Thus, ultimately EOC is not ovarian in origin but rather is secondary, and it is logical to conclude that the only true primary ovarian neoplasms are germ cell and gonadal stromal tumors analogous to tumors in the testis. If this new model is confirmed, it has profound implications for the early detection and treatment of "ovarian cancer."

Molecular pathogenesis and extraovarian origin of epithelial ovarian cancer--shifting the paradigm

Recent morphologic, immunohistochemical, and molecular genetic studies have led to the development of a new paradigm for the pathogenesis and origin of epithelial ovarian cancer based on a dualistic model of carcinogenesis that divides epithelial ovarian cancer into 2 broad categories designated types I and II. Type I tumors comprise low-grade serous, low-grade endometrioid, clear cell and mucinous carcinomas, and Brenner tumors. They are generally indolent, present in stage I (tumor confined to the ovary), and are characterized by specific mutations, including KRAS, BRAF, ERBB2, CTNNB1, PTEN, PIK3CA, ARID1A, and PPP2R1A, which target specific cell signaling pathways. Type I tumors rarely harbor TP53 mutations and are relatively stable genetically. Type II tumors comprise high-grade serous, high-grade endometrioid, malignant mixed mesodermal tumors (carcinosarcomas), and undifferentiated carcinomas. They are aggressive, present in advanced stage, and have a very high frequency of TP53 mutations but rarely harbor the mutations detected in type I tumors. In addition, type II tumors have molecular alterations that perturb expression of BRCA either by mutation of the gene or by promoter methylation. A hallmark of these tumors is that they are genetically highly unstable. Recent studies strongly suggest that fallopian tube epithelium (benign or malignant) that implants on the ovary is the source of low-grade and high-grade serous carcinoma rather than the ovarian surface epithelium as previously believed. Similarly, it is widely accepted that endometriosis is the precursor of endometrioid and clear cell carcinomas and, as endometriosis, is thought to develop from retrograde menstruation; these tumors can also be regarded as involving the ovary secondarily. The origin of mucinous and transitional cell (Brenner) tumors is still not well established, although recent data suggest a possible origin from transitional epithelial nests located in paraovarian locations at the tuboperitoneal junction. Thus, it now appears that type I and type II ovarian tumors develop independently along different molecular pathways and that both types develop outside the ovary and involve it secondarily. If this concept is confirmed, it leads to the conclusion that the only true primary ovarian neoplasms are gonadal stromal and germ cell tumors analogous to testicular tumors. This new paradigm of ovarian carcinogenesis has important clinical implications. By shifting the early events of ovarian carcinogenesis to the fallopian tube and endometrium instead of the ovary, prevention approaches, for example, salpingectomy with ovarian conservation, may play an important role in reducing the burden of ovarian cancer while preserving hormonal function and fertility.

Nuclear envelope structural defects cause chromosomal numerical instability and aneuploidy in ovarian cancer

BACKGROUND

Despite our substantial understanding of molecular mechanisms and gene mutations involved in cancer, the technical approaches for diagnosis and prognosis of cancer are limited. In routine clinical diagnosis of cancer, the procedure is very basic: nuclear morphology is used as a common assessment of the degree of malignancy, and hence acts as a prognostic and predictive indicator of the disease. Furthermore, though the atypical nuclear morphology of cancer cells is believed to be a consequence of oncogenic signaling, the molecular basis remains unclear. Another common characteristic of human cancer is aneuploidy, but the causes and its role in carcinogenesis are not well established.

METHODS

We investigated the expression of the nuclear envelope proteins lamin A/C in ovarian cancer by immunohistochemistry and studied the consequence of lamin A/C suppression using siRNA in primary human ovarian surface epithelial cells in culture. We used immunofluorescence microscopy to analyze nuclear morphology, flow cytometry to analyze cellular DNA content, and fluorescence in situ hybridization to examine cell ploidy of the lamin A/C-suppressed cells.

RESULTS

We found that nuclear lamina proteins lamin A/C are often absent (47%) in ovarian cancer cells and tissues. Even in lamin A/C-positive ovarian cancer, the expression is heterogeneous within the population of tumor cells. In most cancer cell lines, a significant fraction of the lamin A/C-negative population was observed to intermix with the lamin A/C-positive cells. Down regulation of lamin A/C in non-cancerous primary ovarian surface epithelial cells led to morphological deformation and development of aneuploidy. The aneuploid cells became growth retarded due to a p53-dependent induction of the cell cycle inhibitor p21.

CONCLUSIONS

We conclude that the loss of nuclear envelope structural proteins, such as lamin A/C, may underlie two of the hallmarks of cancer--aberrations in nuclear morphology and aneuploidy.

High-grade fimbrial-ovarian carcinomas are unified by altered p53, PTEN and PAX2 expression

High-grade endometrioid and serous carcinomas of the ovary and fallopian tube are responsible for the majority of cancer deaths and comprise a spectrum that includes early or localized (tubal intraepithelial carcinoma) and advanced (invasive or metastatic) disease. We subdivided a series of these tumors into three groups, (1) classic serous, (2) mixed serous and endometrioid and (3) endometrioid carcinomas and determined: (1) the frequencies of coexisting tubal intraepithelial carcinoma, (2) frequency of a dominant ovarian mass suggesting an ovarian origin and (3) immuno-localization of WT-1, p53, PTEN, PAX2 and p16(ink4). All tumors were analyzed for p53 mutations. Thirty six, 25 and 8% of groups 1-3 were associated with tubal intraepithelial carcinoma (P=0.09) and 34, 45 and 62% predominated in one ovary (P=0.028), respectively. Differences in frequencies of diffuse p53 immunostaining (85-93%), WT-1 (70-98%) and p16(ink4) positivity (69-75%) were not significant for all groups. Greater than 95% reduction in PAX2 and PTEN occurred in 67-75 and 5-12%, respectively; however, PAX2 and PTEN staining intensity, when present, was often heterogeneous, highlighting different tumor populations. PAX2 and PTEN expression were markedly reduced or absent in 12 of 12 and 4 of 12 tubal intraepithelial carcinomas. In summary, high-grade müllerian carcinomas share identical frequencies of altered or reduced expression of p53, PTEN and PAX2, all of which can be appreciated in tubal intraepithelial carcinomas. Because only a subset of these tumors appears to arise in the fallopian tube, attention to expression of these biomarkers in the ovary and other müllerian sites might facilitate the identification of other carcinogenic pathways. PAX2 and PTEN, in addition to p53 and p16(ink4), comprise a potentially important gene combination in high-grade pelvic carcinogenesis.

CD44 and p53 immunoexpression patterns in NF1 neoplasms - indicators of malignancy and infiltration

Neurofibromatosis type 1 (NF1) provides a unique system to evaluate the complete range of neoplastic expressions, from encapsulated benignity to invasiveness and malignancy. This study was aimed at determining whether CD44 and p53 may serve as indicators of malignant progression of neurofibroma. CD44, a transmembrane glycoprotein receptor for hyaluronic acid, and participates in cell-extracellular matrix interactions and migration. CD44 may play a vital role, either through under or overexpression, with invasion and metastases of tumors, altering their ability to infiltrate the adjacent tissue. The tumor suppressor gene, p53, has also been implicated in malignant progression of various human tumors including malignant peripheral nerve sheath tumors (MPNST). A total of 44 tumors from 33 patients with NF1 were evaluated with an anti-human CD44H, CD44 splice variant v6 and anti-p53 monoclonal antibodies. Morphologic expression patterns of expression were evaluated for CD44 while semiquantitative criteria were applied to assess, p53 nuclear positivity. Immunoexpression of p53 was markedly higher in 12 of 16 MPNST (75%). Thirteen of 28 (46%) benign neurofibroma also had some expression of p53 above 'normal level', although much lower than the MPNST. Plexiform neurofibroma did not differ from other benign lesions in their expression of p53. Our results suggest that p53 mutation as evidenced by immunohistochemical overexpression is a factor in malignant transformation and progression of neurofibroma. 70% of benign neurofibroma demonstrated some, usually focal, CD44 positivity. The pattern of CD44 expression in plexiform neurofibroma was revealing, as it was maximal in the 'nonencapsulated' portions of the tumors. Eight of 11 (72%) locally infiltrative cutaneous neurofibroma and 13 of 16 (81%) MPNST exhibited diffuse CD44 positivity. CD44v6 expression was positive in control tissues but was not identified in any of tumor samples. Also, within the confines of encapsulated tumors CD44 expression is limited, while in poorly circumscribed neurofibroma CD44 expression is upregulated. This is interpreted as a reflection of the interaction of CD44+ tumor cells with extracellular matrix, hence facilitating infiltrative behavior.