Phospho-STAT5 expression is associated with poor prognosis of human colonic adenocarcinoma

Expression and prognostic role of STAT5a across cancer types

Studies examining the role of signal transducer and activator of transcription 5 (STAT5) in various cancers have produced controversial results. To address this controversy, we examined the prognostic role of STAT5a in cancer patients across multiple cancers. Transcription levels of STAT5a between tumors and normal tissues, obtained from public databases, were analyzed for statistical differences using Cox regression analysis with the outcome as overall survival and covariate of interest as high STAT5a expression. Meta-analysis was then conducted to summarize the hazard ratio estimate from the Cox regression analyses. We found that STAT5a was significantly under-expressed in breast, lung, and ovarian cancers, while STAT5a was significantly overexpressed in lymphoid neoplasm diffuse large B-cell lymphoma, glioblastoma, and glioma. High STAT5a expression was significantly associated with favorable survival in bladder cancer (lnHR = -0.8689 [-1.4087, -0.3292], P-value = 0.0016), breast cancer (lnHR = -0.7805 [-1.1394, -0.4215], P-value < 0.0001) and lung cancer (lnHR = -0.3255 [-0.6427, -0.0083], P-value = 0.0443). After adjusting for clinicopathological factors, high STAT5a expression remained significantly associated with favorable survival in breast cancer (lnHR = -0.6091 [-1.0810, -0.1372], P-value = 0.0114). These results suggest that higher STAT5a expression is associated with favorable overall survival in breast cancer, and therefore might have protective effects, and that STAT5a expression could be a potential prognostic biomarker, especially in breast cancer. However, the prognostic role of STAT5a is dependent on cancer type.

Growth hormone and gastrointestinal malignancy: An intriguing link

Growth hormone (GH) excess is associated with several systemic complications, one of which is the increased risk of neoplastic processes particularly of the gastrointestinal (GI) tract. Among the GI neoplasms, the most reported association is with benign and malignant neoplasms of the colon. In the majority of published literature, an increased incidence of GI neoplasms, both colonic adenomas as well as colorectal carcinoma is reported. However, the studies on colon cancer-specific mortality rate are conflicting with recent studies reporting similar cancer-specific mortality rates in comparison to controls. Many studies have reported an association of colorectal neoplasms with GH levels. Pathogenic mechanisms put forward to explain this association of GH excess and GI neoplasms primarily involve the increased GH-insulin-like growth factor 1 (IGF-1) signaling. Both GH and IGF-1 have proliferative, anti-apoptotic, and angiogenic effects on the systemic tissues leading to cellular proliferation. Other contributing factors to the increased risk of GI neoplasms include slow intestinal transit with a redundant large bowel, altered bile acids, deranged local immune response, shared genetic susceptibility factors and hyperinsulinemia. In view of the increased risk association, most guidelines for the care of acromegaly patients recommend an initial screening colonoscopy. Recommendations for further follow-up colonoscopy differ but broadly, the guidelines agree that it depends on the findings at first colonoscopy and state of remission of GH excess. Regarding the concern about the risk of colorectal cancers in patients receiving recombinant GH therapy, most cohort studies do not show an increased risk.

Pharmacological Modulation of the Crosstalk between Aberrant Janus Kinase Signaling and Epigenetic Modifiers of the Histone Deacetylase Family to Treat Cancer

Hyperactivated Janus kinase (JAK) signaling is an appreciated drug target in human cancers. Numerous mutant JAK molecules as well as inherent and acquired drug resistance mechanisms limit the efficacy of JAK inhibitors (JAKi). There is accumulating evidence that epigenetic mechanisms control JAK-dependent signaling cascades. Like JAKs, epigenetic modifiers of the histone deacetylase (HDAC) family regulate the growth and development of cells and are often dysregulated in cancer cells. The notion that inhibitors of histone deacetylases (HDACi) abrogate oncogenic JAK-dependent signaling cascades illustrates an intricate crosstalk between JAKs and HDACs. Here, we summarize how structurally divergent, broad-acting as well as isoenzyme-specific HDACi, hybrid fusion pharmacophores containing JAKi and HDACi, and proteolysis targeting chimeras for JAKs inactivate the four JAK proteins JAK1, JAK2, JAK3, and tyrosine kinase-2. These agents suppress aberrant JAK activity through specific transcription-dependent processes and mechanisms that alter the phosphorylation and stability of JAKs. Pharmacological inhibition of HDACs abrogates allosteric activation of JAKs, overcomes limitations of ATP-competitive type 1 and type 2 JAKi, and interacts favorably with JAKi. Since such findings were collected in cultured cells, experimental animals, and cancer patients, we condense preclinical and translational relevance. We also discuss how future research on acetylation-dependent mechanisms that regulate JAKs might allow the rational design of improved treatments for cancer patients. SIGNIFICANCE STATEMENT: Reversible lysine-ɛ-N acetylation and deacetylation cycles control phosphorylation-dependent Janus kinase-signal transducer and activator of transcription signaling. The intricate crosstalk between these fundamental molecular mechanisms provides opportunities for pharmacological intervention strategies with modern small molecule inhibitors. This could help patients suffering from cancer.

Involvement of STAT5 in Oncogenesis

Signal transducer and activator of transcription (STAT) proteins, and in particular STAT3, have been established as heavily implicated in cancer. Recently, the involvement of STAT5 signalling in the pathology of cancer has been shown to be of increasing importance. STAT5 plays a crucial role in the development of the mammary gland and the homeostasis of the immune system. However, in various cancers, aberrant STAT5 signalling promotes the expression of target genes, such as cyclin D, Bcl-2 and MMP-2, that result in increased cell proliferation, survival and metastasis. To target constitutive STAT5 signalling in cancers, there are several STAT5 inhibitors that can prevent STAT5 phosphorylation, dimerisation, or its transcriptional activity. Tyrosine kinase inhibitors (TKIs) that target molecules upstream of STAT5 could also be utilised. Consequently, since STAT5 contributes to tumour aggressiveness and cancer progression, inhibiting STAT5 constitutive activation in cancers that rely on its signalling makes for a promising targeted treatment option.

Long non-coding RNA RP11-468E2.5 curtails colorectal cancer cell proliferation and stimulates apoptosis via the JAK/STAT signaling pathway by targeting STAT5 and STAT6

BACKGROUND

Long non-coding RNAs (lncRNAs) are tumor-associated biological molecules and have been found to be implicated in the progression of colorectal cancer (CRC). This study aims to examine the effects of lncRNA RP11-468E2.5 and its target genes (STAT5 and STAT6) on the biological activities of CRC cells via the Janus kinase-signal transducer and activator of transcription (JAK/STAT) signaling pathway.

METHODS

We initially screened the GEO database for differentially expressed lncRNAs related to CRC and then made a prediction of the implicated target genes. Then we collected CRC tissues and adjacent normal tissues from 169 CRC patients. Human CRC HCT116 and SW480 cells were treated with small interference RNA (siRNA) against RP11-468E2.5, AG490 (an inhibitor of the JAK/STAT signaling pathway), or both in combination. Next, we measured the effects of RP11-468E2.5 treatment on cellular activities such as cell viability, cycle distribution and cell apoptosis, and studied interactions among RP11-468E2.5, STAT5/STAT6, and the JAK/STAT signaling pathway. Finally, an in vivo tumor formation assay was performed to observe the effect of RP11-468E2.5 on tumor growth.

RESULTS

The CRC-related gene microarray data showed low expression of RP11-468E2.5 in CRC surgical specimens. However, RP11-468E2.5 was confirmed to target STAT5 and STAT6, which participate in the JAK/STAT signaling pathway. CRC tissues showed lower expression of RP11-468E2.5, higher expression of STAT5, STAT6 and of the cell cycle marker Cyclin D1 (CCND1), compared to the findings in adjacent normal tissues. The treatment of siRNA against RP11-468E2.5 increased expression of JAK2, STAT3, STAT5, STAT6, CCND1 and Bcl-2 along with the extent of STAT3, STAT5 and STAT6 phosphorylation, while lowering expression of P21 and P27. Treatment with AG490 exhibited approximately opposite effects, whereas siRNA against RP11-468E2.5 treatment stimulated CRC cell proliferation and reduced cell apoptosis, while promoting cell cycle entry; AG490 treatment reversed these results.

CONCLUSIONS

Altogether, we conclude that up-regulation of RP11-468E2.5 inhibits the JAK/STAT signaling pathway by targeting STAT5 and STAT6, thereby suppressing cell proliferation and promoting cell apoptosis in CRC.

Balancing STAT Activity as a Therapeutic Strategy

Driven by dysregulated IL-6 family member cytokine signaling in the tumor microenvironment (TME), aberrant signal transducer and activator of transcription (STAT3) and (STAT5) activation have been identified as key contributors to tumorigenesis. Following transformation, persistent STAT3 activation drives the emergence of mesenchymal/cancer-stem cell (CSC) properties, important determinants of metastatic potential and therapy failure. Moreover, STAT3 signaling within tumor-associated macrophages and neutrophils drives secretion of factors that facilitate metastasis and suppress immune cell function. Persistent STAT5 activation is responsible for cancer cell maintenance through suppression of apoptosis and tumor suppressor signaling. Furthermore, STAT5-mediated CD4+/CD25+ regulatory T cells (T_regs) have been implicated in suppression of immunosurveillance. We discuss these roles for STAT3 and STAT5, and weigh the attractiveness of different modes of targeting each cancer therapy. Moreover, we discuss how anti-tumorigenic STATs, including STAT1 and STAT2, may be leveraged to suppress the pro-tumorigenic functions of STAT3/STAT5 signaling.

STAT5 expression correlates with recurrence and survival in melanoma patients treated with interferon-α

Interferons (IFN) have a direct growth-inhibiting effect on tumor cells through Janus kinase-dependent activation of the transcription factor signal transducer and activator of transcription (STAT1). In vitro, signaling through STAT5 has been demonstrated to counteract this effect and lead to IFN resistance of melanoma cell lines. In 32 patients treated with IFN-α in an adjuvant setting, we investigated paraffin-embedded tumor tissue from primary melanomas and melanoma metastases for expression of STAT3 and STAT5, by immunohistochemistry, and for expression of phosphorylated signaling transduction activating transcription factor (pSTAT)3 and pSTAT5, by immunofluorescence. Tumor cell expression levels of these proteins were correlated with patient characteristics and clinical outcomes. The patient cohort consisted of 12 (37.5%) patients at AJCC stage I/II (primary melanoma) and 20 (62.5%) at stage III/IV (metastatic melanoma). Recurrence was observed for 25 (78.1%) either during or after IFN-α therapy. χ Correlation of staining intensities with clinical data revealed association of pSTAT3 and STAT5 expression with sex (P=0.003 and 0.016, respectively) and of STAT3 with tumor stage (P=0.019). Recurrence of melanoma was found to be associated with high STAT5 expression (P=0.017). Multivariable regression analysis revealed STAT5 expression as an independent factor for predicting progression-free survival (P<0.0001) and overall survival (P=0.022). In summary, high expression of STAT5 correlated with melanoma recurrence and survival of patients treated with IFN-α in the adjuvant setting. Recently, it has been suggested that mutations of Janus kinases are involved in resistance to immune checkpoint blocker treatments implying a possible role of STAT5 for immune checkpoint resistance.

Colonic Cancer and Acromegaly

Acromegaly results in a significantly increased morbidity and mortality due to cardiovascular and respiratory complications, as well as malignancies arising mainly from the colon. Furthermore, an increased lifetime risk of malignant transformation of pre-malignant colonic lesions relates to a worse overall prognosis from colorectal cancer, which is currently considered a major disease-related complication. In this review we provide some insight into colonic changes in this condition, summarize current knowledge and evidence on the use of colonoscopic screening in patients with acromegaly, and suggest a recommended screening protocol.

GPx2 Induction Is Mediated Through STAT Transcription Factors During Acute Colitis

BACKGROUND

The selenoprotein glutathione peroxidase 2 (GPx2) is highly expressed in the gastrointestinal epithelium. During inflammatory bowel disease and colorectal cancer, GPx2 expression is enhanced.

METHODS

We analyzed GPx2 expression and transcriptional regulation during the different phases of dextran sulfate sodium (DSS)-induced colitis in mice and in cytokine-treated colorectal cancer cells.

RESULTS

In the colon of DSS-treated mice, GPx2 was upregulated during the acute and recovery phase. In the latter, it was specifically localized in regenerating ki67-positive crypts next to ulcerations. In cultured cells, endogenous GPx2 expression and GPx2 promoter activity were enhanced by the anti-inflammatory mediators 15-deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2) and interleukin-22 (IL-22), while it was unaffected by classical proinflammatory cytokines like IL-1β. Induction of GPx2 expression by 15d-PGJ2 was mediated through Nrf2. In contrast, in DSS-treated Nrf2-KO mice GPx2 expression remained upregulated during recovery, which appeared to be independent of Nrf2. IL-22 activates transcription factors of the signal transducers and activators of transcription (STAT) family. Therefore, we analyzed the GPx2 promoter for putative STAT-responsive elements and identified 4 of them. Point mutation of the binding element next to the transcription start completely abolished promoter activation after IL-22 treatment and after cotransfection of STAT expression plasmids. To show in vivo relevance of the obtained results, we performed immunohistochemistry for phospho-STAT3 and GPx2. Especially during acute colitis, GPx2 and nuclear STAT3 colocalized in inflamed areas.

CONCLUSIONS

GPx2 is a novel target of STAT transcription factors. The upregulation of GPx2 by IL-22 indicates that GPx2 might be important for the resolution of inflammation.

The prevalence and associated factors of colorectal neoplasms in acromegaly: a single center based study

PURPOSE

Colorectal neoplasms are well known to be a complication in cases of acromegaly; however, data on the prevalence of colorectal neoplasms in Asian patients with acromegaly are limited. Further, the factors associated with colorectal neoplasms in cases of acromegaly are controversial. Therefore, we aimed to clarify the prevalence of and factors associated with colorectal neoplasms in Japanese patients with acromegaly in a single center.

METHODS

We analyzed consecutive 57 patients who had undergone full-length colonoscopy at the time of diagnosis at Kobe University Hospital between 1986 and 2012.

RESULTS

Of the 57 patients, 22 (38.6%), 18 (31.6%) and 3 (5.3%) patients were diagnosed with hyperplastic polyps, adenomas, and adenocarcinomas, respectively and the prevalence was significantly higher than in a historical control group, Chinese patients with irritable bowel syndrome (The odds ratio was 4.0, 8.7, and 17.5, respectively). The prevalence of adenocarcinomas was also significantly higher in these patients than in the general Japanese population (odds ratio 14.5). Patients with acromegaly who had colorectal neoplasms had longer disease duration than those without colorectal neoplasms. Of note, the area under the growth hormone (GH) concentration-time curve (GH AUC) during the oral glucose tolerance test was significantly higher in patients with adenocarcinomas than in those with no colonic lesion or those with hyperplastic polyps.

CONCLUSION

Japanese patients with acromegaly exhibited an increased risk of colorectal neoplasms, especially colorectal adenocarcinomas. An increased GH AUC was associated with an increased risk for colon adenocarcinomas in patients with acromegaly.

Functions and regulation of MUC13 mucin in colon cancer cells

BACKGROUND

MUC13 is overexpressed and aberrantly localized in colon cancer tissue; however, the specific functions and regulation of MUC13 expression are unknown.

METHODS

Stable cell lines with either overexpressed or suppressed MUC13 levels were analyzed to determine cell growth, colony formation, cell migration, and cell invasion assays. The molecular mechanisms involved in MUC13 regulation were elucidated via chromatin immunoprecipitation (ChIP) and analysis of interleukin 6 (IL6) treatments. Colon cancer tissues were analyzed by immunohistochemistry (IHC) for the protein levels of MUC13 and P-STAT5 in colon cancer cells.

RESULTS

Overexpression of MUC13 increased cell growth, colony formation, cell migration, and invasion. In concordance, MUC13 silencing decreased these tumorigenic features. Overexpression of MUC13 also modulated various cancer-associated proteins, including telomerase reverse transcriptase, sonic hedgehog, B cell lymphoma murine like site 1, and GATA like transcription factor 1. Additionally, MUC13-overexpressing cells showed increased HER2 and P-ERK expression. ChIP analysis revealed binding of STAT5 to the predicted MUC13 promoter. IL6 treatment of colon cancer cells increased the expression of MUC13 via activation of the JAK2/STAT5 signaling pathway. Suppression of JAK2 and STAT5 signaling by chemical inhibitors abolished IL6-induced MUC13 expression. IHC analysis showed increased expression of both P-STAT5 and MUC13 in colon cancer as compared to adjacent normal tissue.

CONCLUSIONS

The results of this study, for the first time, suggest functional roles of MUC13 in colon cancer progression and provide information regarding the regulation of MUC13 expression via JAK2/STAT5 which may reveal promising therapeutic approaches for colon cancer treatment.