Raf Kinase Inhibitor Protein Expression and Prognostic Value in Soft Tissue Sarcomas

Cancer resistance via the downregulation of the tumor suppressors RKIP and PTEN expressions: therapeutic implications

The Raf kinase inhibitor protein (RKIP) has been reported to be underexpressed in many cancers and plays a role in the regulation of tumor cells' survival, proliferation, invasion, and metastasis, hence, a tumor suppressor. RKIP also regulates tumor cell resistance to cytotoxic drugs/cells. Likewise, the tumor suppressor, phosphatase and tensin homolog (PTEN), which inhibits the phosphatidylinositol 3 kinase (PI3K)/AKT pathway, is either mutated, underexpressed, or deleted in many cancers and shares with RKIP its anti-tumor properties and its regulation in resistance. The transcriptional and posttranscriptional regulations of RKIP and PTEN expressions and their roles in resistance were reviewed. The underlying mechanism of the interrelationship between the signaling expressions of RKIP and PTEN in cancer is not clear. Several pathways are regulated by RKIP and PTEN and the transcriptional and post-transcriptional regulations of RKIP and PTEN is significantly altered in cancers. In addition, RKIP and PTEN play a key role in the regulation of tumor cells response to chemotherapy and immunotherapy. In addition, molecular and bioinformatic data revealed crosstalk signaling networks that regulate the expressions of both RKIP and PTEN. These crosstalks involved the mitogen-activated protein kinase (MAPK)/PI3K pathways and the dysregulated nuclear factor-kappaB (NF-κB)/Snail/Yin Yang 1 (YY1)/RKIP/PTEN loop in many cancers. Furthermore, further bioinformatic analyses were performed to investigate the correlations (positive or negative) and the prognostic significance of the expressions of RKIP or PTEN in 31 different human cancers. These analyses were not uniform and only revealed that there was a positive correlation between the expression of RKIP and PTEN only in few cancers. These findings demonstrated the existence of signaling cross-talks between RKIP and PTEN and both regulate resistance. Targeting either RKIP or PTEN (alone or in combination with other therapies) may be sufficient to therapeutically inhibit tumor growth and reverse the tumor resistance to cytotoxic therapies.

A 30-Year Long-Term Experience in Appendix Neuroendocrine Neoplasms-Granting a Positive Outcome

Neuroendocrine neoplasms (NENs) are the most common tumor of the appendix and have an excellent prognosis. Appendiceal tumors diagnosed between 1989 and 2019 were reviewed, and clinical data were collected from patient files. Part of the series was immuno-profiled for markers related to cell cycle proliferation and/or senescence-type, apoptotic, and metastatic potential. Appendix NENs were detected in 74 patients, with 0.47% of incidence per appendectomy. The median age of the patients was 21.5 years, with two age peaks of incidence at 17.0 and 55.2 years. The median tumors size was 5.8 mm, and most were smaller than 10 mm. Lymphovascular and perineural invasion, as well as necrosis, was associated with larger tumor size. G1 tumors composed 96.0% of the cohort. The presence of moderate/strong p16 and the absent/low Bcl-2 expression was frequently observed and associated with a smaller size. This study represents one of the largest cohorts and with a long follow-up. For tumors smaller than 10 mm appendicectomy was sufficient as a curative procedure, as revealed by the good outcome. This series presented a 100% disease-free survival. The indolent phenotype of appendix NENs is supported by the expression of markers that point towards a strong inhibition of cell replication and growth inhibition.

RKIP as an Inflammatory and Immune System Modulator: Implications in Cancer

Raf kinase inhibitor protein (RKIP), an important modulator of intracellular signalling pathways, is commonly downregulated in multiple cancers. This reduction, or loss of expression, is correlated not only with the presence of metastasis, contributing to RKIP’s classification as a metastasis suppressor, but also with tumour aggressiveness and poor prognosis. Recent findings suggest a strong involvement of RKIP in the modulation of tumour microenvironment components, particularly by controlling the infiltration of specific immune cells and secretion of pro-metastatic factors. Additionally, RKIP interaction with multiple signalling molecules seems to potentiate its function as a regulator of inflammatory processes, mainly through stimulation of anti- or pro-inflammatory cytokines. Furthermore, RKIP is involved in the modulation of immunotherapeutic drugs response, through diverse mechanisms that sensitize cells to apoptosis. In the present review, we will provide updated information about the role of RKIP as an inflammatory and immune modulator and its potential implications in cancer will be addressed.

Current Status of Raf Kinase Inhibitor Protein (RKIP) in Lung Cancer: Behind RTK Signaling

Lung cancer is the most deadly neoplasm with the highest incidence in both genders, with non-small cell lung cancer (NSCLC) being the most frequent subtype. Somatic mutations within the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene are key drivers of NSCLC progression, with EGFR inhibitors being particularly beneficial for patients carrying the so-called “EGFR-sensitizing mutations”. However, patients eventually acquire resistance to these EGFR inhibitors, and a better knowledge of other driven and targetable proteins will allow the design of increasingly accurate drugs against patients’ specific molecular aberrations. Raf kinase inhibitory protein (RKIP) is an important modulator of relevant intracellular signaling pathways, including those controlled by EGFR, such as MAPK. It has been reported that it has metastasis suppressor activity and a prognostic role in several solid tumors, including lung cancer. In the present review, the potential use of RKIP in the clinic as a prognostic biomarker and predictor of therapy response in lung cancer is addressed.

Loss of Raf kinase inhibitor protein expression is associated with human papillomavirus 16 infection in anal tumors

There has been an increase in the incidence of anal cancer in the past two decades, with squamous cell carcinoma (SCC) being the most frequent histological type identified. Among the risk factors, high-risk human papillomavirus (HPV) infection is the most pervasive. Raf kinase inhibitor protein (RKIP) is expressed in a number of normal human tissues and previous studies have demonstrated the prognostic value of the loss of RKIP expression in several gastrointestinal tumors. Therefore, the present study aimed to evaluate the clinical implications of RKIP expression in a series of neoplastic lesions of the anal canal. The resected tumors of 48 patients [8 high-grade intraepithelial lesions (HSILs), 14 adenocarcinomas and 26 squamous cell carcinomas (SCCs)] were immunohistochemically evaluated for RKIP expression, and the results were correlated with clinicopathological data. The results identified a decreased 5-year overall survival rate in patients with adenocarcinoma (40.8%) compared with patients with SCC (76.7%), and a decreased 5-year disease-free survival rate in patients at clinical stages III/IV (37.3 vs. 62.5 and 82.6% for clinical stages 0 and I/II, respectively). Low RKIP expression was revealed in 62.5% of HSILs, 88.5% of SCCs and 100.0% of the adenocarcinomas. High RKIP expression was associated with patient ethnicity (37.5% in non-Caucasians vs. 7.5% in Caucasians) and patient age (33.3% in younger patients vs. 0.0% in older patients). Finally, high RKIP expression was correlated with HPV16 infection status (40% in HPV^- vs. 5.3% in HPV⁺ patients). A correlation was identified between high RKIP expression and lesions with a generally improved prognosis, such as those diagnosed in younger patients, in situ lesions and lesions of lower clinical grades; there was also a negative correlation between high RKIP expression and HPV16 positivity in patients.