K-ras oncogene mutation in cancer and precancerous lesions of the gallbladder

Gallbladder Cancer: Current Insights in Genetic Alterations and Their Possible Therapeutic Implications

Simple Summary

Knowledge of genetic alterations in gallbladder cancer (GBC) continues to increase. This systematic review provides an overview of frequently occurring genetic alterations in GBC and describes their possible therapeutic implications. We detected three frequently (>5%) altered genes (ATM, ERBB2 and PIK3CA) for which targeted therapies are available in other cancer types. For solid cancers with microsatellite instability or a high tumor mutational burden pembrolizumab is FDA-approved. Altogether, these five biomarkers might be used in future molecular panels to enable precision medicine for patients with GBC. We found only nine clinical trials evaluating targeted therapies in GBC directed at frequently altered genes (ERBB2, ARID1A, ATM and KRAS). This underlines the challenges to perform such clinical trials in this rare, heterogeneous cancer type and emphasizes the need for multicenter clinical trials.

Abstract

Due to the fast progression in molecular technologies such as next-generation sequencing, knowledge of genetic alterations in gallbladder cancer (GBC) increases. This systematic review provides an overview of frequently occurring genetic alterations occurring in GBC and their possible therapeutic implications. A literature search was performed utilizing PubMed, EMBASE, Cochrane Library, and Web of Science. Only studies reporting genetic alterations in human GBC were included. In total, data were extracted from 62 articles, describing a total of 3893 GBC samples. Frequently detected genetic alterations (>5% in >5 samples across all studies) in GBC for which targeted therapies are available in other cancer types included mutations in ATM, ERBB2, and PIK3CA, and ERBB2 amplifications. High tumor mutational burden (TMB-H) and microsatellite instability (MSI-H) were infrequently observed in GBC (1.7% and 3.5%, respectively). For solid cancers with TMB-H or MSI-H pembrolizumab is FDA-approved and shows an objective response rates of 50% for TMB-H GBC and 41% for MSI-H biliary tract cancer. Only nine clinical trials evaluated targeted therapies in GBC directed at frequently altered genes (ERBB2, ARID1A, ATM, and KRAS). This underlines the challenges to perform such clinical trials in this rare, heterogeneous cancer type and emphasizes the need for multicenter clinical trials.

Skp2 is an independent prognosticator of gallbladder carcinoma among p27(Kip1)-interacting cell cycle regulators: an immunohistochemical study of 62 cases by tissue microarray

Despite improvement in surgical techniques, prognosis of gallbladder carcinoma remains poor. It is desirable to identify prognostic biomarkers to aid in the development of targeted therapeutic strategies. Two SCF(Skp2) ubiquitin ligase-related proteins, Skp2 and cyclin-dependent kinase subunit 1 (Cks1), are involved in post-transcriptional degradation of p27(Kip1) tumor suppressor, which inhibits both cdk2/cyclin E and cdk2/cyclin A complexes and thus prevents transition to the S phase. However, the prognostic utility of p27(Kip1)-interacting cell cycle regulators has not been systematically assessed in gallbladder carcinoma. Immunohistochemistry was performed for p27(Kip1), Skp2, Cks1, cyclin E, cyclin A, and Ki-67 in tissue microarrays of 62 gallbladder carcinomas with follow-up. The data were correlated with clinicopathological features and overall survival (OS). The cumulative OS rate for all 62 cases was 42.9% at 3 years. Aberrant labeling indices (LIs) of p27(Kip1) (<20%), cyclin E (>or=5%), cyclin A (>or=5%), Cks1 (>or=40%), and Skp2 (>or=10%) were identified in 29, 58, 66, 21, and 57% of gallbladder carcinomas, respectively. By log-rank tests, downregulation of p27(Kip1) (P=0.0319) and high LIs of Skp2 (P=0.0006), Cks1 (P=0.0460), cyclin E (P=0.0070), and Ki-67 (P=0.0037) were predictive of inferior OS. Furthermore, the combined expression status of Skp2 and Ki-67 robustly defined three prognostically different groups (P=0.0001). In multivariate comparison, Skp2 overexpression represented the strongest independent adverse prognosticator (P=0.004, risk ratio (RR): 5.538), followed by Ki-67 LI >or=50% (P=0.016, RR: 3.254) and American Joint Committee on Cancer stages II-IV (P=0.013, RR: 3.163). In conclusion, aberrations of p27(Kip1)-interacting cell cycle regulators are common in gallbladder carcinomas. Skp2 overexpression is highly representative of biological aggressiveness and independently associated with poor OS, suggesting that it is a promising novel target for therapeutic intervention in aggressive cases. The combined assessment of Skp2 and Ki-67 LIs effectively risk-stratifies gallbladder carcinomas with different prognosis, which is worth being prospectively validated in future study.

Biliary tract cancers: current concepts and controversies

Biliary tract cancer, which consists of gall bladder cancer and cholangio-carcinoma, presents many challenges to practising physicians. It is a relatively rare cancer that often causes a diagnostic dilemma, as its presentation may be similar to that of non-malignant conditions. In many cases, histological or cytological confirmation of a cancer diagnosis is not possible preoperatively. The management of this disease is also complex due to a morbid patient population and limited data on the optimal therapeutic approach. Surgery remains the mainstay of treatment, although the extent of resection required is still debated. The role of adjuvant therapy is also controversial, but a combined modality approach appears to be beneficial in patients with a high risk of recurrence, such as those with node positive tumors or positive resection margins. When surgery is not possible, the prognosis of patients with biliary tract cancer is very poor. In unresectable patients, the combination of chemotherapy and radiotherapy can result in a prolonged survival for some patients. In the palliative setting, biliary stenting and other supportive measures can alleviate symptoms and improve survival. Gemcitabine-based combination chemotherapy may also provide successful palliation and has achieved response rates of approximately 30% and a median survival of > 15 months in one study. Ultimately, treatment decisions should be individualised and participation in clinical trials is encouraged. Further progress in the management of biliary tract cancer is anticipated using biological therapies and continued research is essential to discover the optimal treatment for this challenging disease.

Gallbladder cancer: current status

Gallbladder cancer (GBC) is the most common biliary tract malignancy. There is a tremendous regional variability in its incidence. Risk factors include genetic susceptibility, gender, presence of gallstones, chronic biliary infections, diet and some anatomical anomalies. Several genetic abnormalities have been described which may be aetiologically important as well as carry prognostic significance. These include mutations in the proteins K-RAS and P53, and altered expression of P-glycoprotein, COX-2 and epidermal growth factor receptor. Most patients present at an advanced stage, overall prognosis is very poor. TNM stage and the extent of surgical resection are the most important prognostic factors. Surgery is the only curative therapy reserved for patients with early-stage disease. The role of adjuvant therapy is not fully defined. Patients with advanced disease are managed with systemic chemotherapy that is primarily palliative. Although 5-fluorouracil alone, or in combination, has been most commonly utilised, there is much greater enthusiasm for the combination of cisplatin and gemcitabine. The availability of better drugs and combinations may affect the use of chemotherapy in neoadjuvant and adjuvant settings. Novel targeted therapies require exploration alone or in combination with chemotherapy.

In Situ and Invasive Adenocarcinomas of the Gallbladder Extending Into or Arising From Rokitansky-Aschoff Sinuses

We report 49 cases of gallbladder carcinomas that extended into or originated from Rokitansky-Aschoff sinuses (RAS), all of which were resected by laparoscopic cholecystectomy. Twenty-one tumors were in situ carcinomas that extended along RAS; six in situ carcinomas arose in adenomyomatous hyperplasia and 22 were invasive adenocarcinomas with extension into RAS. Thirty-seven patients were women and 12 men. Forty patients had cholelithiasis. The age of the patients ranged from 55 to 84 years (mean 67 years). All in situ carcinomas were incidental microscopic findings in gallbladders removed for cholelithiasis and/or cholecystitis. No patient with in situ carcinoma died as a result of the tumor, including two with in situ carcinoma that originated in adenomyomatous hyperplasia and showed microinvasion. In contrast, of 15 patients with invasive well to moderately differentiated adenocarcinoma extending into RAS and invading the muscle layer or subserosal connective tissue, 8 died 2 to 4 years after surgery. Seven patients survived 1 to 8 years after cholecystectomy. Useful clues to separate RAS with in situ carcinoma from tubular neoplastic invasive glands were the following: connection of the epithelial invaginations to the surface epithelium, recognition of normal biliary epithelium admixed with neoplastic epithelium, presence of inspissated bile in long dilated spaces, and lack of invasion to the smooth muscle bundles. In situ carcinoma spreading along RAS consisted of long tubular often dilated structures extending through the intermuscular connective tissue, whereas neoplastic glands were usually small or of medium size that invaded smooth muscle bundles or intermuscular connective tissue. Perineural invasion was seen only in invasive glands located in the subserosal connective tissue. Two cases of in situ carcinoma that arose in adenomyomatous hyperplasia and three invasive adenocarcinomas that were composed predominantly of tall columnar mucin containing cells similar to gastric foveolar cells with varying degrees of atypia and cells with biliary phenotype bear some resemblance to intraductal papillary mucinous carcinoma of the pancreas or to mucinous cystic pancreatic neoplasm. Metaplastic pyloric glands often seen in the muscle layer and subserosal connective tissue maintain their lobular pattern and should not be confused with invasive glands. Our findings indicate that distinction of in situ carcinoma spreading into RAS from tubular neoplastic glands of invasive adenocarcinomas is crucial to determine prognosis in this group of patients with gallbladder carcinoma.

Progression of gene hypermethylation in gallstone disease leading to gallbladder cancer

BACKGROUND

Aberrant methylation of tumor-suppressor genes is associated with a loss of gene function that can afford selective growth advantages to sporadic neoplastic cells arising during gallbladder inflammation.

METHODS

Fifty-four gallbladder neoplasms were selected from tumor banks in the United States and Chile. Each of the neoplasms was subjected to methylation-specific polymerase chain reaction to detect promoter methylation associated with six candidate tumor-suppressor genes (p16, APC, methylguanine methyltransferase, hMLH1, retinoic acid receptor beta-2, and p73) implicated in multiple human cancer types.

RESULTS

Aberrant methylation of any of the six candidate tumor-suppressor genes was detected in 72% of the gallbladder neoplasms, 28% of the cases of chronic cholecystitis, and in only 1 of the 15 normal gallbladder controls. The four most commonly methylated genes in the gallbladder cancers were p16 (56%), p73 (28%), APC (27%), and hMLH1 (14%). Significant differences in gene methylation were discovered between US gallbladder cancers and those from Chile, where gallbladder cancer is one of the leading causes of cancer-related deaths. APC methylation was present in 42% of the US cases but in only 14% of the Chilean tumors (P =.028). p73 methylation was common among the Chilean cancers (40%) compared with those from the United States (13%; P =.034).

CONCLUSIONS

The acquisition of hypermethylation at multiple tumor-suppressor gene-promoter sites may contribute to tumor formation and progression within the chronically inflamed gallbladder. The apparent differences in methylation patterns among the Chilean and US gallbladder cases may indicate a unique biology associated with this cancer in different parts of the world.

Immunohistochemical and genetic analysis of non-small cell and small cell gallbladder carcinoma and their precursor lesions

Gallbladder carcinomas can be highly lethal neoplasms. Relatively little is known about the genetic abnormalities that underlie these tumors, particularly with respect to their timing in neoplastic progression. The authors evaluated 5 noninvasive dysplasias and 33 invasive gallbladder carcinomas (6 small cell carcinomas, 27 non-small cell carcinomas, of which 16 were accompanied by an in situ carcinoma component) for expression of the protein products of the p16, p53, Dpc4, and pRB tumor suppressor genes by immunohistochemistry. Neoplasms were also evaluated for the presence of activating K-ras oncogene mutations. Seventy-five percent of non-small cell gallbladder carcinomas demonstrated loss of p16 expression, whereas 63% accumulated high levels of p53. Loss of Dpc4 and pRB expression was less frequent, seen in 19% and 4% of the neoplasms, respectively. Thirty percent of neoplasms harbored activating K-ras mutations. In contrast, 100% of the small cell carcinomas of the gallbladder demonstrated inactivation of the pRB/p16 pathway; 67% showed loss of pRB expression, and the other 33% lost p16 expression. Eighty-three percent of small cell carcinomas accumulated high levels of p53, whereas loss of Dpc4 expression and activating K-ras mutations were not found. Among 15 evaluable in situ components, 13 harbored the same alterations found in the invasive component. Inactivation of p16 and p53 occur in the majority of non-small cell gallbladder carcinomas. Dpc4 inactivation and K-ras mutations occur in a significant minority of cases. pRB loss is uncommon in non-small cell gallbladder carcinoma, but virtually all small cell carcinomas inactivate the p16/pRB pathway, usually by retinoblastoma protein loss. It is noteworthy that all of these alterations occur at the level of carcinoma in situ.

Gene-specific oxidative DNA damage in Helicobacter pylori-infected human gastric mucosa

To study the status of oxidative DNA damage in Helicobacter pylori infection in more detail, we examined oxidative DNA damage to individual genes by determining the loss of PCR product of a targeted gene before and after gastric mucosal DNA was treated with 8-hydroxyguanine glycosylase, which cleaves DNA at the 8-hydroxyguanine residues. The results showed that, of the 5 genes tested, p53, insulin-like growth factor II receptor and transforming growth factor-beta receptor type II showed significant oxidative DNA damage in H. pylori-positive tissues and that the BAX and beta-ACTIN genes were relatively undamaged. These results suggest that in H. pylori infection, oxidative DNA damage does not occur homogeneously throughout the genomic DNA but, rather, in a gene-specific manner. We conclude that the progressive accumulation of preferential oxidative DNA damage in certain genes, such as p53, likely contributes to gastric carcinogenesis.

Biliary tract cancer

Advances in cellular and molecular biology of extrahepatic cholangiocarcinoma and gallbladder adenocarcinoma are providing innovative means for the diagnosis and treatment of biliary tract cancer. Similarly, refinements in noninvasive studies--including helical computed tomography, magnetic resonance cholangiopancreatography, and endoscopic ultrasonography--are enabling more accurate diagnosis, staging, and treatment planning for these tumors. Complete resection remains the only means for cure, and recent reports from major hepatobiliary centers support aggressive wide resection for bile duct and gallbladder cancer. Palliation of malignant strictures has improved with advanced endoscopic techniques, newer polyurethane-covered stents, endoscopic microwave coagulation therapy, and radiofrequency intraluminal endohyperthermia. The preliminary data on such minimally invasive techniques suggest an improvement in quality of life and survival for selected patients.