Genome-wide mutational landscape of mucinous carcinomatosis peritonei of appendiceal origin

Systemic chemotherapy before cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) in patients with high-grade mucinous carcinoma peritonei of appendiceal origin

BACKGROUND

The role of systemic chemotherapy (SC) before cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) in appendiceal high-grade mucinous carcinoma peritonei (HGMCP) is controversial. We analyzed the effect of SC prior to CRS/HIPEC in HGMCP.

METHODS

A prospective database of CRS/HIPEC procedures for HGMCP without signet ring cells and with signet ring cells (HGMCP-S) from 1998 to 2017 was reviewed. Exclusion criteria was prior surgery >5 regions or >2 regimens of prior SC. Perioperative variables were analyzed.

RESULTS

There were 140 HGMCP/HGMCP-S identified: 64 with prior SC (preSC) and 76 without (noSC). Groups were balanced for lymph node status, complete cytoreduction rate, disease burden, complications, and postoperative SC. PreSC had more HGMCP-S, moderately/poorly differentiated histology, and longer time-to-surgery (median: 6 vs 2 months, p < 0.001). Median overall survival (mOS) was 40 vs 86 and median progression-free survival (mPFS) was 19 vs 43 months for preSC vs noSC, respectively (p = 0.006 and p = 0.007). In HGMCP-S subanalysis, mOS was 25 vs 39 and mPFS 16 vs 29 months for preSC vs noSC, respectively (p = 0.188 and p = 0.063). In moderately/poorly differentiated histology subanalysis, mOS was 38 vs 56 and mPFS 18 vs 29 months in preSC vs noSC, respectively (p = 0.199 and 0.082). Prior SC was not linked to improved OS or PFS in non-signet ring HGMCP or well-differentiated histology subanalysis.

CONCLUSION

Prior SC was not associated with less disease burden, better cytoreduction rates, or improved clinical outcomes in HGMCP, regardless of histopathologic subtype. Traditional SC agents may not be effective in HGMCP in the neoadjuvant setting.

Selection and Characteristics of Patients with Peritoneal Dissemination from Appendiceal Cancer with Exceptional/Poor Survival After CRS/HIPEC

BACKGROUND

Survival in peritoneal dissemination from appendiceal cancer after complete cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) varies within each histopathologic subtype. Analyzing patients with unique responses may uncover the mechanisms behind their extreme outcomes. We proposed a method to identify retrospectively and to characterize patients who responded exceptionally well or very poorly within each histopathologic subtype.

METHODS

Retrospective review of patients with low-grade mucinous carcinoma peritonei (LGMCP), high-grade MCP (HGMCP), and HGMCP with signet ring cells (HGMCP-S) with complete CRS/HIPEC (CC-0/1) was performed. Patients were divided by recurrence status. Median follow-up was calculated for each. Exceptional responders (ExR) were defined as alive without recurrence after median follow-up of the nonrecurrent group. Poor responders (PoR) were defined as disease recurrence before median follow-up of the recurrent group. Perioperative characteristics were analyzed.

RESULTS

LGMCP, HGMCP, and HGMCP-S had 48 (41%), 19 (23%), and 7 (14%) ExR and 11 (10%), 20 (24%), and 20 (39%) PoR, respectively. All ExR had lower median PCI (26 vs. 36 [p = 0.004]; 13 vs. 33.5 [p < 0.001]; 3 vs. 29.5 [p = 0.001]). Fewer LGMCP and HGMCP ExR had abnormal tumor markers (36% vs. 90% [p = 0.003]; 22% vs. 74% [p = 0.003]). More HGMCP and HGMCP-S ExR had CC-0 (vs. CC-1) cytoreductions (84% vs. 50%, p = 0.041; 100% vs. 40%, p = 0.008).

CONCLUSIONS

Stratifying patients by recurrence status and follow-up time successfully selects ExR and PoR within each histopathologic subtype. Perioperative characteristics of ExR versus PoR differ across histopathologic subtypes, except for disease burden. Genetic analysis may further elucidate differences and aid in the development of novel targeted therapies.

Molecular Diagnostics in the Neoplasms of Small Intestine and Appendix: 2018 Update

Neoplasms of the small intestine are rare in comparison with colorectal tumors. The most common tumor types arising in the small intestine are adenocarcinomas, well-differentiated neuroendocrine tumors, gastrointestinal stromal tumors, and lymphoma. Primary appendiceal neoplasms are rare and found in less than 2% of appendectomy specimens with an incidence of approximately 1.2 cases per 100,000 people per year in the United States. This article explores molecular diagnostics in the neoplasms of small intestine and appendix.

Pseudomyxoma Peritonei After a Total Pancreatectomy for Intraductal Papillary Mucinous Neoplasm With Colloid Carcinoma in Lynch Syndrome

We report a case of pseudomyxoma peritonei (PMP) arising in a 62-year-old male patient with Lynch syndrome (LS). The patient's medical history included an adenocarcinoma of the colon for which a right hemicolectomy was performed and a pancreatectomy due to an intraductal papillary mucinous neoplasm (IPMN) with invasive colloid carcinoma. It was considered that the PMP could be a metastasis of the earlier colonic or pancreatic carcinoma. The pancreatic carcinoma, colon carcinoma, and PMP tissues were examined, and immunohistochemical and molecular analyses were performed to determine the PMP origin. Histopathologic examination revealed morphological similarities with the pancreatic colloid carcinoma, and further immunohistochemical and molecular analyses, including a shared GNAS mutation, confirmed the pancreatic origin of the PMP. In conclusion, this is a unique case of a patient with LS presenting with PMP originating from an IPMN with invasive colloid carcinoma, several years after pancreatectomy. The present case has important diagnostic implications. The IPMN should be considered as a rare extracolonic manifestation of LS, and pancreatic carcinoma origin should be considered in patients presenting with PMP. This case report highlights the added value of molecular diagnostics in daily pathology practice.

Outcomes in Peritoneal Dissemination from Signet Ring Cell Carcinoma of the Appendix Treated with Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

BACKGROUND

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) is standard treatment for peritoneal dissemination from appendiceal cancer (AC); however, its role in high-grade histopathologic subtypes (high-grade mucinous carcinoma peritonei [HGMCP] and HGMCP with signet ring cells [HGMCP-S]) is controversial due to their aggressive behavior. This study analyzed clinical outcomes of high-grade AC after CRS/HIPEC.

METHODS

A prospective database of CRS/HIPEC procedures for HGMCP performed from 1998-2017 was reviewed. Perioperative variables and survival were analyzed.

RESULTS

Eighty-six HGMCP and 65 HGMCP-S were identified. HGMCP had more positive tumor markers (TM) (CEA/CA-125/CA-19-9) than HGMCP-S (63% vs 40%, p = 0.005). HGMCP had higher Peritoneal Cancer Index (32 vs 26, p = 0.097) and was less likely to have positive lymph nodes (LN) than HGMCP-S (28% vs 69%, p = < 0.001). Complete cytoreduction was achieved in 84% and 83%, respectively. PFS at 3- and 5-years was 59% and 48% for HGMCP vs 31% and 14% for HGMCP-S. Median PFS was 4.3 and 1.6 years, respectively (p < 0.001). OS at 3- and 5-years was 84% and 64% in HGMCP vs 38% and 25% in HGMCP-S. Median OS was 7.5 and 2.2 years, respectively (p < 0.001). LN negative HGMCP-S had longer median PFS and OS than LN positive HGMCP-S (PFS: 3.4 vs 1.5 years, p = 0.03; OS: 5.6 vs 2.1 months, p = 0.021).

CONCLUSIONS

The aggressive histology of HGMCP-S is associated with poor OS, has fewer abnormal TM, and is more likely to have positive LN. However, CRS/HIPEC can achieve a 5-year survival of 25%, which may improve to 51% with negative LN.

Genomic Landscape of Appendiceal Neoplasms

Purpose

Appendiceal neoplasms are heterogeneous and are often treated with chemotherapy similarly to colorectal cancer (CRC). Genomic profiling was performed on 703 appendiceal cancer specimens to compare the mutation profiles of appendiceal subtypes to CRC and other cancers, with the ultimate aim to identify potential biomarkers and novel therapeutic targets.

Methods

Tumor specimens were submitted to a Clinical Laboratory Improvement Amendments-certified laboratory (Foundation Medicine, Cambridge, MA) for hybrid-capture-based sequencing of 3,769 exons from 315 cancer-related genes and 47 introns of 28 genes commonly rearranged in cancer. Interactions between genotype, histologic subtype, treatment, and overall survival (OS) were analyzed in a clinically annotated subset of 76 cases.

Results

There were five major histopathologic subtypes: mucinous adenocarcinomas (46%), adenocarcinomas (30%), goblet cell carcinoids (12%), pseudomyxoma peritonei (7.7%), and signet ring cell carcinomas (5.2%). KRAS (35% to 81%) and GNAS (8% to 72%) were the most frequent alterations in epithelial cancers; APC and TP53 mutations were significantly less frequent in appendiceal cancers relative to CRC. Low-grade and high-grade tumors were enriched for GNAS and TP53 mutations, respectively (both χ² P < .001). GNAS and TP53 were mutually exclusive (Bonferroni corrected P < .001). Tumor grade and TP53 mutation status independently predicted OS. The mutation status of GNAS and TP53 strongly predicted OS (median, 37.1 months for TP53 mutant v 75.8 GNAS-TP53 wild type v 115.5 GNAS mutant; log-rank P = .0031) and performed as well as grade in risk stratifying patients.

Conclusion

Epithelial appendiceal cancers and goblet cell carcinoids show differences in KRAS and GNAS mutation frequencies and have mutation profiles distinct from CRC. This study highlights the benefit of performing molecular profiling on rare tumors to identify prognostic and predictive biomarkers and new therapeutic targets.

Glycomic Profiling Highlights Increased Fucosylation in Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a subtype of mucinous adenocarcinoma that most often originates from the appendix, and grows in the peritoneal cavity filling it with mucinous ascites. KRAS and GNAS mutations are frequently found in PMP, but other common driver mutations are infrequent. As altered glycosylation can promote carcinogenesis, we compared N-linked glycan profiles of PMP tissues to those of normal appendix. Glycan profiles of eight normal appendix samples and eight low-grade and eight high-grade PMP specimens were analyzed by mass spectrometry. Our results show differences in glycan profiles between PMP and the controls, especially in those of neutral glycans, and the most prominent alteration was increased fucosylation. We further demonstrate up-regulated mRNA expression of four fucosylation-related enzymes, the core fucosylation performing fucosyltransferase 8 and three GDP-fucose biosynthetic enzymes in PMP tissues when compared with the controls. Up-regulated protein expression of the latter three enzymes was further observed in PMP cells by immunohistochemistry. We also demonstrate that restoration of fucosylation either by salvage pathway or by introduction of an expression of intact GDP-mannose 4,6-dehydratase enhance expression of MUC2, which is the predominant mucin molecule secreted by the PMP cells, in an intestinal-derived adenocarcinoma cell line with defective fucosylation because of deletion in the GDP-mannose 4,6-dehydratase gene. Thus, altered glycosylation especially in the form of fucosylation is linked to the characteristic mucin production of PMP. Glycomic data are available via ProteomeXchange with identifier PXD010086.

Genomics of Peritoneal Malignancies

The peritoneum protects the intraabdominal organs. This function is exploited by aggressive cancers originating from organs within the abdomen, resulting in peritoneal metastasis. We discuss genomic variants that may lead to peritoneal metastasis from multiple cancers. Peritoneal malignancies are attributed to epithelial-mesenchymal transition. These metastatic lesions harbor similar genetic mutations to the primary tumor yet may manifest clone-specific aberrations that promote propagation. Peritoneal metastasis are increasingly being treated with surgical resection as an adjunct to radiation, chemotherapy, and other biologic therapies. We describe genetic and genomic variances that are predictive markers for metastasis and burgeoning indicators for peritoneal malignancies.

Analysis of Mutation and Loss of Heterozygosity by Whole-Exome Sequencing Yields Insights into Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a clinical syndrome characterized by gross mucinous ascites originating from a disseminated intraperitoneal neoplasm. Although typically confined to the abdomen, mortality is high if untreated. Biomarkers, including genetic mutation profiles, may aid treatment selection and decision making. We applied whole-exome sequencing to five patients diagnosed with low-grade appendiceal mucinous neoplasms, using paired tumor and germline samples identify biomarkers. Multiple bioinformatic approaches were applied to these data to assess both somatic mutation profiles and loss of heterozygosity events. Mutation profiles of the tumors were consistent with deamination of methylcytosine being the prevailing mechanism. Pathogenic mutations were identified in both KRAS and GNAS in all samples, and further mutations in genes implicated in PMP, namely FGFR2, APC, SMAD2, and FAT4. No TP53 somatic mutations were identified, matching expectations for low-grade tumors. Four of five samples exhibited clonal loss of heterozygosity; these regions were further examined and found to contain genes harboring pathogenic somatic mutations in some samples. RNF43 was hereby implicated in the pathogenesis of PMP of appendiceal origin, having previously been found to increase sensitivity to Wnt signaling and to have involvement in similar mucinous tumors. In conclusion, we have investigated the mutation profile of PMP of appendiceal origin and provided the first report of RNF43 involvement in its progression.

Mutational landscape of goblet cell carcinoids and adenocarcinoma ex goblet cell carcinoids of the appendix is distinct from typical carcinoids and colorectal adenocarcinomas

There is limited data on the spectrum of molecular alterations in goblet cell carcinoids and adenocarcinoma ex goblet cell carcinoids of the appendix. We used next generation sequencing to determine mutations of potential pathogenetic and therapeutic significance in this rare group of tumors. Adequate DNA was successfully extracted in 34/46 cases and the final group included 18 goblet cell carcinoids and 16 adenocarcinoma ex goblet cell carcinoids. Illumina TruSeq™ was used for sequencing exons of a custom 282 gene panel using an Illumina HiSeq 2000. All cases had a minimum coverage depth of at least 50 reads. After filtering through the Exome Sequencing Project, the number of mutations per case ranged from 0-9 (mean:3). The mutational burden in adenocarcinoma ex goblet cell carcinoids was significantly higher than goblet cell carcinoids (mean 5 vs. 3; p < 0.05) but the spectrum of alterations overlapped between the two groups. The most frequent mutations included ARID1A (4/34), ARID2 (4/34), CDH1 (4/34), RHPN2 (4/34), and MLL2 (3/34). Some mutations typically seen in conventional colorectal adenocarcinomas were also identified but with much lower frequency (APC :4/34; KRAS :2/34). MLL2 and KRAS mutations were only seen in adenocarcinoma ex goblet cell carcinoids and TP53 mutations were limited to poorly differentiated adenocarcinoma ex goblet cell carcinoids (2/34). Copy number changes could be evaluated in 15/34 cases and showed low copy number gains in CDKN1B (6/15) and NFKBIA (6/15), among others. The overlapping molecular alterations suggest that goblet cell carcinoids and adenocarcinoma ex goblet cell carcinoids are best considered two grades of differentiation of the same tumor rather than two distinct histological types. Mutations in TP53, CDH1 and MLL2 mutations were predominantly present in the adenocarcinoma ex goblet cell carcinoid group consistent with transformation to a higher grade lesion. The unique mutational profile also offers an explanation for the poor chemosensitivity in these tumors and highlights the need for developing new targeted therapies.

Can low grade PMP be divided into prognostically distinct subgroups based on histological features? A retrospective study and the importance of using the appropriate classification

INTRODUCTION

The pathological classification of PMP of appendiceal origin has prognostic and treatment implications. Our goals were to • Classify low grade mucinous carcinoma peritonei (LGMCP) into prognostically distinct subgroups based on histological features. • Compare the reproducibility of the WHO and the PSOGI classifications for both PMP and the appendiceal primary tumor.

PATIENTS AND METHODS

A retrospective analysis of patients undergoing CRS and HIPEC or debulking surgery was done. All the tumors were re-classified according to the PSOGI classification. LGMCP was further classified into three histological subgroups and the impact on survival was evaluated.

RESULTS

From Jun 2011 to June 2016, 101 patients underwent CRS with HIPEC (n = 89) or debulking surgery (n=12). The median PCI was 28 (3-39) and 74.1% patients had CC-0/1 resections. Of the 76.2% patients who had LGMCP, 4 patients (5.1%) were classified as group 1, 54 (70.1%) as group 2 and 19 patients (24.6%) as group 3. At a median follow up of 21 months, the disease free survival was not reached, 30 months and 14 months for groups 1, 2 and 3 respectively (p = 0.09). There was no difference in overall survival. Using the WHO classification, there was a discordance in the grade of the primary tumor and the peritoneal lesions in 19.8% and conflicting terminology was used in 62% of patients.

CONCLUSIONS

The subgroups of LGMCP described here are prognostically different though this needs further prospective evaluation in larger series. The PSOGI classification is more uniformly reproducible and should be preferred to the WHO classification.

The curious case of Gαs gain-of-function in neoplasia

BACKGROUND

Mutations activating the α subunit of heterotrimeric Gs protein are associated with a number of highly specific pathological molecular phenotypes. One of the best characterized is the McCune Albright syndrome. The disease presents with an increased incidence of neoplasias in specific tissues.

MAIN BODY

A similar repertoire of neoplasms can develop whether mutations occur spontaneously in somatic tissues during fetal development or after birth. Glands are the most "permissive" tissues, recently found to include the entire gastrointestinal tract. High frequency of activating Gαs mutations is associated with precise diagnoses (e.g., IPMN, Pyloric gland adenoma, pituitary toxic adenoma). Typically, most neoplastic lesions, from thyroid to pancreas, remain well differentiated but may be a precursor to aggressive cancer.

CONCLUSIONS

Here we propose the possibility that gain-of-function mutations of Gαs interfere with signals in the microenvironment of permissive tissues and lead to a transversal neoplastic phenotype.

Targeting G-protein coupled receptor-related signaling pathway in a murine xenograft model of appendiceal pseudomyxoma peritonei

Cancer cells aberrantly express mucins to enhance their survival. Relative chemoresistance of appendiceal pseudomyxoma peritonei (PMP) is attributed to abundant extracellular mucin 2 (MUC2) protein production. We hypothesized that simultaneous MUC2 inhibition and apoptosis induction would be effective against mucinous tumors. In vitro studies were conducted using LS174T cells (MUC2-secreting human colorectal cancer cells), PMP explant tissue, and epithelial organoid cultures (colonoids) derived from mucinous appendix cancers. In vivo studies were conducted using murine intraperitoneal patient-derived xenograft model of PMP. We found COX-2 over-expression in PMP explant tissue, which is known to activate G-protein coupled EP4/cAMP/PKA/CREB signaling pathway. MUC2 expression was reduced in vitro by small molecule inhibitors targeting EP4/PKA/CREB molecules and celecoxib (COX-2 inhibitor), and this was mediated by reduced CREB transcription factor binding to the MUC2 promoter. While celecoxib (5-40 µM) reduced MUC2 expression in vitro in a dose-dependent fashion, only high-dose celecoxib (≥ 20 µM) decreased cell viability and induced apoptosis. Chronic oral administration of celecoxib decreased mucinous tumor growth in our in vivo PMP model via a combination of MUC2 inhibition and induction of apoptosis. We provide a preclinical rationale for using drugs that simultaneously inhibit MUC2 production and induce apoptosis to treat patients with PMP.

Clinical Benefit from Trametinib in a Patient with Appendiceal Adenocarcinoma with a GNAS R201H Mutation

We report the case of a patient with appendiceal adenocarcinoma with mucinous peritoneal carcinomatosis who was treated with trametinib upon identification of a GNAS R201H mutation by comprehensive genomic profiling. The molecular pathology of appendiceal neoplasms is reviewed, and the mechanistic basis underlying the clinical benefit as well as the subsequent course on trametinib that were observed in this patient are discussed.

KRAS and GNAS Co-Mutation in Metastatic Low-Grade Appendiceal Mucinous Neoplasm (LAMN) to the Ovaries: A Practical Role for Next-Generation Sequencing

Patient: Female, 49

Final Diagnosis: Metastatic LAMN

Symptoms: Abdominal discomfort

Medication: —

Clinical Procedure: Laparoscopic total abdominal hysterectomy • bilateral salpingo-oophorectomy • complete supracolic omentectomy • appendectomy

Specialty: Oncology

Multiple components of PKA and TGF-β pathways are mutated in pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is a subtype of mucinous adenocarcinoma mainly restricted to the peritoneal cavity and most commonly originating from the appendix. The genetic background of PMP is poorly understood and no targeted treatments are currently available for this fatal disease. While RAS signaling pathway is affected in most if not all PMP cases and over half of them also have a mutation in the GNAS gene, other genetic alterations and affected pathways are, to a large degree, poorly known. In this study, we sequenced whole coding genome of nine PMP tumors and paired normal tissues in order to identify additional, commonly mutated genes and signaling pathways affected in PMP. These exome sequencing results were validated with an ultra-deep amplicon sequencing method, leading to 14 validated variants. The validated results contain seven genes that contribute to the protein kinase A (PKA) pathway. PKA pathway, which also contains GNAS, is a major player of overproduction of mucin, which is the characteristic feature of PMP. In addition to PKA pathway, we identified mutations in six genes that belong to the transforming growth factor beta (TGF-β) pathway, which is a key regulator of cell proliferation. Since either GNAS mutation or an alternative mutation in the PKA pathway was identified in 8/9 patients, inhibition of the PKA pathway might reduce mucin production in most of the PMP patients and potentially suppress disease progression.

High Expression of Aldolase B Confers a Poor Prognosis for Rectal Cancer Patients Receiving Neoadjuvant Chemoradiotherapy

Background : Colorectal cancer is the third most common cancer in both sex worldwide and it is also the fourth most common cause of cancer mortality. For rectal cancer, neoadjuvant concurrent chemoradiotherapy (CCRT) followed by radical proctectomy is gold standard treatment for patients with stage II/III rectal cancer. By data mining a documented database of rectal cancer transcriptome (GSE35452) from Gene Expression Omnibus, National Center of Biotechnology Information, we recognized that ALDOB was the most significantly up-regulated transcript among those related to glycolysis (GO: 0006096). Hence, we analyzed the clinicopathological correlation and prognostic effect of ALDOB protein (Aldolase B), which encoded by ALDOB gene. Methods : ALDOB immunostain was performed in 172 rectal adenocarcinomas treated with preoperative chemoradiotherapy followed by radical surgery, which were divided into high- and low-expression groups. Furthermore, statistical analyses were examined to correlate the relationship between ALDOB immunoreactivity and important clinical and pathological characteristics, as well as three survival indices: disease-specific survival (DSS), local recurrence-free survival (LRFS) and metastasis-free survival (MeFS). Results : ALDOB (Aldolase B) over-expression was significantly associated with pre-CCRT and post-CCRT tumor advancement, lymphovascular invasion, perineural invasion and poor response to CCRT (all P ≤ .023). In addition, ALDOB high expression was linked to adverse DSS, LRFS and MeFS in univariate analysis (P ≤ .0075) and also served as an independent prognosticator indicating dismal DSS and MeFS in multivariate analysis (hazard ratio (HR) = 3.462, 95% confidence interval (CI): 1.263-9.495; HR = 2.846, 95% CI: 1.190-6.808, respectively). Conclusion : ALDOB (Aldolase B) may play an imperative role in rectal cancer progression and responsiveness to neoadjuvant CCRT, and serve as a novel prognostic biomarker. Additional researches to clarify the molecular and biochemical pathways are essential for developing promising ALDOB-targeted therapies for patients with rectal cancers.

Droplet-Based Digital PCR: Application in Cancer Research

The efficient characterization of genetic and epigenetic alterations in oncology, virology, or prenatal diagnostics requires highly sensitive and specific high-throughput approaches. Nevertheless, with the use of conventional methods, sensitivity and specificity were largely limited. By partitioning individual target molecules within distinct compartments, digital PCR (dPCR) could overcome these limitations and detect very rare sequences with unprecedented precision and sensitivity. In dPCR, the sample is diluted such that each individual partition will contain no more than one target sequence. Following the assay reaction, the dPCR process provides an absolute value and analyzable quantitative data. The recent coupling of dPCR with microfluidic systems in commercial platforms should lead to an essential tool for the management of patients with cancer, especially adapted to the analysis of precious samples. Applications in cancer research range from the analysis of tumor heterogeneity to that of a range of body fluids. Droplet-based dPCR is indeed particularly appropriate for the emerging field of liquid biopsy analysis. In this review, following an overview of the development in dPCR technology and different strategies based on the use of microcompartments, we will focus particularly on the applications and latest development of microfluidic droplet-based dPCR in oncology.

"The Jelly Belly": Diagnostic Dilemmas and Current Concepts

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare and poorly understood clinicopathological entity characterized by gelatinous ascites with neoplastic or non-neoplastic mucinous implants in the peritoneum. Although its origin was debated, current evidence in literature favours the appendix as the origin of the disease, over the ovaries. The changing terminologies in the classification of this entity pose diagnostic and management challenges.

CASE REPORTS

Herein, we report three cases of PMP in postmenopausal women, their clinical presentation, pathological staging based on the peritoneal tumor deposits and the treatment administered. Two patients recovered uneventfully, while one had recurrence of adenocarcinoma.

CONCLUSION

The rarity of this disease and the diagnostic challenges associated with it are discussed with an emphasis on the current concepts in its origin and management. Appropriate classification and complete removal of the tumor is mandated to prevent disease-related mortality.

GNAS Mutations: Drivers or Co-Pilots? Yet, Promising Diagnostic Biomarkers

Over 25 years ago, GNAS mutations were discovered associated with McCune-Albright syndrome (MAS) and pituitary tumors. The mutant gene, encoding the heterotrimeric Gs protein, was named 'derived from Gs Protein' (gsp) oncogene. For a long time, gsp remained associated with specific endocrine tumors. Recently, high frequencies of gsp were reported for a rapidly growing number of neoplasms in the gastrointestinal tract. Will heterotrimeric G-proteins follow small G-proteins and become recognized as cancer biomarkers and therapeutic targets?

Pathophysiology and classification of pseudomyxoma peritonei

Background: The term pseudomyxoma peritonei (PMP) was first described in 1884 and there has been much debate since then over the term. A recent consensus of world experts agreed that PMP should be thought of as a clinical entity characterised by the presence of mucinous ascites, omental cake, peritoneal implants and possibly ovarian involvement. It generally originates from mucinous appendiceal tumours. Content: This review details the clinical presentation of this unusual condition, presents the new classification system and how this relates to outcome. The pathophysiology of this disease is also explored with a special reference to the relationship of the disease to tumour markers. Summary: A classification system has been agreed upon by the leading experts in PMP which is now divided into low and high grade mucinous carcinomatosis peritonei. This distinction correlates with clinical outcome as does the presence of raised tumour markers preoperatively. Outlook: Research needs to be focused on understanding the factors associated with poor prognosis through well designed multi-centred prospective studies. This will allow us to identify patients with bad tumour biology so that targeted treatment based on likely prognosis may then become a reality.

Management of Appendix Cancer

Primary cancers of the appendix are rare and are frequently diagnosed after surgery for appendicitis, presumed ovarian primary malignancy, or other indications. Primary appendix cancers are histologically diverse, and classification of these tumors has historically been confusing because of the nonstandardized nomenclature that is used. This review aimed to describe the epidemiology, presentation, workup, staging, and management of primary appendix cancers using current, recommended nomenclature. For this purpose, tumors were broadly classified as colonic-type or mucinous adenocarcinoma, goblet cell adenocarcinoma, or neuroendocrine carcinoma. Signet ring cell carcinoma was not regarded as an individual entity. The presence of signet ring cells is a histologic feature that may or may not be present in colonic-type or mucinous adenocarcinoma. The management of primary appendix cancer is complex and is dependent on the histologic subtype and extent of disease. Randomized, prospective trials do not exist for these rare tumors and management is largely guided by retrospective data expert consensus guidelines, which are summarized here.

The impact of stage, grade, and mucinous histology on the efficacy of systemic chemotherapy in adenocarcinomas of the appendix: Analysis of the National Cancer Data Base

BACKGROUND

Adenocarcinomas of the appendix represent a heterogeneous disease depending on the presence of mucinous histology, histologic grade, and stage. In the current study, the authors sought to explore the interplay of these factors with systemic chemotherapy in a large population data set.

METHODS

Patients in the National Cancer Data Base (NCDB) who were diagnosed with mucinous, nonmucinous, and signet ring cell-type appendiceal neoplasms from 1985 through 2006 were selected. Multivariable Cox proportional hazards regression models were developed.

RESULTS

A total of 11,871 patients met the inclusion criteria for the current study: 50.3% had mucinous neoplasms, 40.5% had nonmucinous neoplasms, and 9.2% had signet ring cell-type neoplasms. The 5-year overall survival (OS) stratified by grade was similar among patients with American Joint Committee on Cancer stage I to stage III disease but not for those with stage IV disease. The median OS for patients with stage IV mucinous and nonmucinous tumors was 6.4 years and 2.3 years, respectively, for those with well differentiated histology (P<.0001) and was 1.5 years and 0.8 years, respectively, for those with poorly differentiated histology (P<.0001). In multivariable modeling for stage I to III disease, adjuvant chemotherapy improved OS for both mucinous and nonmucinous histologies, with hazard ratios (HRs) of 0.78 (95% confidence interval [95% CI], 0.68-0.89 [P = .0002]) and 0.83 (95% CI, 0.74-0.94 [P = .002]), respectively. For patients with stage IV disease, systemic chemotherapy significantly improved OS for those with nonmucinous (HR, 0.72; 95% CI, 0.64-0.82 [P<.0001]) but not mucinous (HR, 0.95; 95% CI, 0.86-1.04 [P = .2) histologies, although this was grade-dependent. The median OS for chemotherapy versus no chemotherapy was 6.4 years versus 6.5 years (P value not significant) for patients with mucinous, well-differentiated tumors and 1.6 years versus 1.0 years (P = .0007) for patients with mucinous, poorly differentiated tumors.

CONCLUSIONS

Adjuvant chemotherapy demonstrated a significant OS benefit regardless of histology. However, for patients with stage IV disease, the benefit of systemic chemotherapy varied by tumor histology and grade, with patients with well-differentiated, mucinous, appendiceal adenocarcinomas deriving no survival benefit from systemic chemotherapy. Cancer 2016;122:213-221. © 2015 American Cancer Society.

Pseudomyxoma peritonei diagnosed 19 years after appendicectomy

Pseudomyxoma peritonei (PMP) is an uncommon clinical finding describing the intraperitoneal accumulation of abundant mucinous, jelly-like material. This entity may represent a spectrum of diseases ranging from mucinous ascites, commonly associated with ruptured epithelial tumours of the appendix, to frank mucinous carcinomatosis. In cases of appendiceal origin, the patient may present with signs and symptoms of acute appendicitis, and thus careful diagnosis must be made in order to correctly and appropriately guide management. This may include a combination of surgical debulking with or without intraperitoneal or systemic chemotherapy. We present a 52-year-old woman with a 4-month history of abdominal pain and distension with a previous appendicectomy 19 years earlier. Radiological and pathological investigations diagnosed a probable PMP secondary to ruptured appendicitis many years ago. We describe her unique case, with emphasis on length of time to diagnosis and clinical management by surgical cytoreduction alone.

Mitogen-activated protein kinase inhibition reduces mucin 2 production and mucinous tumor growth

Excessive accumulation of mucin 2 (MUC2) protein (a gel-forming secreted mucin) within the peritoneal cavity is the major cause of morbidity and mortality in pseudomyxoma peritonei (PMP), a unique mucinous malignancy of the appendix. Mitogen-activated protein kinase (MAPK) signaling pathway is upregulated in PMP and has been shown to modulate MUC2 promoter activity. We hypothesized that targeted inhibition of the MAPK pathway would be a novel, effective, and safe therapeutic strategy to reduce MUC2 production and mucinous tumor growth. We tested RDEA119, a specific MEK1/2 (MAPK extracellular signal-regulated kinase [ERK] kinase) inhibitor, in MUC2-secreting LS174T cells, human PMP explant tissue, and in a unique intraperitoneal murine xenograft model of PMP. RDEA119 reduced ERK1/2 phosphorylation and inhibited MUC2 messenger RNA and protein expression in vitro. In the xenograft model, chronic oral therapy with RDEA119 inhibited mucinous tumor growth in an MAPK pathway-dependent manner and this translated into a significant improvement in survival. RDEA119 downregulated phosphorylated ERK1/2 and nuclear factor κB p65 protein signaling and reduced activating protein 1 (AP1) transcription factor binding to the MUC2 promoter in LS174T cells. This study provides a preclinical rationale for the use of MEK inhibitors to treat patients with PMP.

Mutational landscape of mucinous ovarian carcinoma and its neoplastic precursors

Background

Mucinous ovarian tumors are an unusual group of rare neoplasms with an apparently clear progression from benign to borderline to carcinoma, yet with a controversial cell of origin in the ovarian surface epithelium. They are thought to be molecularly distinct from other ovarian tumors but there have been no exome-level sequencing studies performed to date.

Methods

To understand the genetic etiology of mucinous ovarian tumors and assess the presence of novel therapeutic targets or pathways, we undertook exome sequencing of 24 tumors encompassing benign (5), borderline (8) and carcinoma (11) histologies and also assessed a validation cohort of 58 tumors for specific gene regions including exons 4–9 of TP53.

Results

The predominant mutational signature was of C>T transitions in a NpCpG context, indicative of deamination of methyl-cytosines. As well as mutations in known drivers (KRAS, BRAF and CDKN2A), we identified a high percentage of carcinomas with TP53 mutations (52 %), and recurrent mutations in RNF43, ELF3, GNAS, ERBB3 and KLF5.

Conclusions

The diversity of mutational targets suggests multiple routes to tumorigenesis in this heterogeneous group of tumors that is generally distinct from other ovarian subtypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-015-0210-y) contains supplementary material, which is available to authorized users.

BAP1 mutation is a frequent somatic event in peritoneal malignant mesothelioma

BACKGROUND

Malignant mesothelioma (MM) arises from mesothelial cells that line the pleural, peritoneal and pericardial surfaces. The majority of MMs are pleural and have been associated with asbestos exposure. Previously, pleural MMs have been genetically characterized by the loss of BAP1 (40-60%) as well as loss of NF2 (75%) and CDKN2A (60%). The rare peritoneal form of MM occurs in ~10% cases. With only ~300 cases diagnosed in the US per year, its link to asbestos exposure is not clear and its mutational landscape unknown.

METHODS

We analyzed the somatic mutational landscape of 12 peritoneal MM of epitheloid subtype using copy number analysis (N = 9), whole exome sequencing (N = 7) and targeted sequencing (N = 12).

RESULTS

Peritoneal MM display few copy number alterations, with most samples having less than 10 Mbp total changes, mostly through deletions and no high copy number amplification. Chromosome band 3p21 encoding BAP1 is the most recurrently deleted region (5/9), while, in contrast to pleural MM, NF2 and CDKN2A are not affected. We further identified 87 non-silent mutations across 7 sequenced tumors, with a median of 8 mutated genes per tumor, resulting in a very low mutation rate (median 1.3 10(-6)). BAP1 was the only recurrently mutated gene (N = 3/7). In one additional case, loss of the entire chromosome 3 leaves a non-functional copy of BAP1 carrying a rare nonsense germline variant, thus suggesting a potential genetic predisposition in this patient. Finally, with targeted sequencing of BAP1 in 3 additional cases, we conclude that BAP1 is frequently altered through copy number losses (N = 3/12), mutations (N = 3/12) or both (N = 2/12) sometimes at a sub-clonal level.

CONCLUSION

Our findings suggest a major role for BAP1 in peritoneal MM susceptibility and oncogenesis and indicate important molecular differences to pleural MM as well as potential strategies for therapy and prevention.

Systemic chemotherapy (SC) before cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) in patients with peritoneal mucinous carcinomatosis of appendiceal origin (PMCA)

BACKGROUND

The role of SC before CRS/HIPEC for patients with PMCA is unclear. This study explores the effect of SC prior to CRS/HIPEC on overall survival (OS) in patients with PMCA.

METHODS

72 patients with recently diagnosed PMCA who underwent CRS/HIPEC were identified from a prospective database. Thirty patients had SC before CRS/HIPEC (Group 1) and 42 did not (Group 2). Patients who were referred to our center after multiple lines of SC were excluded from this analysis. OS was estimated.

RESULTS

Median follow-up was 3.2 years. Groups were similar regarding lymph node positivity, postoperative SC and rate of complete cytoreduction. Twenty-four (80%) patients in Group 1 and 21 (50%) in Group 2 had high grade histology (HG) (p = 0.01). OS from CRS/HIPEC at 1, 2, and 3 years was 93, 68, 51% in Group 1 and 82, 64, 60% in Group 2, respectively (p = 0.74). Among HG patients 3-year survival was 36% in the SC group vs. 35% in the group without SC (p = 0.67). The 3-year OS for patients with low grade (LG) tumors was 100% in the SC group vs. 79% in the group with no prior SC (p = 0.26). Among patients with signet ring cell (SRC) histology, 1, 2 and 3-year survival was 94, 67 and 22% in the SC group vs. 43, 14, 14% in the group with no SC, respectively (p = 0.028). There were only 6 patients with LG PMCA who received prior SC.

CONCLUSIONS

Preoperative SC could improve the prognosis of patients with high-grade PMCA with SRC histology.