e14033 Background: Glioblastoma multifome (GBM)is an aggressiveand malignant form of brain cancer, constituting approximately 12-15 % of all primary brain tumors. The prognosis of GBM remains poor despite a multimodal treatment approach; therefore, there remains an urgent need for a novel and effective therapeutic approach. There exist several gene products that regulate immune evasion in GBM and, thus, may be targeted to restore the anti-tumor response in GBM. We hypothesize that the dysregulated RKIP-SNAIL-YY1 axis in GBM is involved in the pathogenesis and immune evasion of GBM. The existence of such an axis would make it amenable to therapeutic targeting. Methods: Delineation of the cross-talk signaling pathways mediated by each of the axis gene products; analyses of immune evasion parameters regulated by each gene product; validation by bioinformatic analyses of the presence of a dysregulated axis in GBM; and various means targeting gene products in the axis. Results: The expression levels of SNAIL and YY1 are upregulated while RKIP expression is downregulated in GBM. Previous findings from our laboratory and others have demonstrated that YY1 regulates the metastasis inducer SNAIL expression and, in turn, SNAIL suppresses the metastasis suppressor and immune inducer RKIP expression. In turn, RKIP inhibits both YY1 and SNAIL via its inhibition of NF-KB-induced transcription of both YY1 and SNAIL. These findings are the result of cross-talk signaling pathways, including the RAF/MEK /ERK, NF-kB, PI3K/AKT pathways. These findings supported the presence of a dysregulated RKIP-SNAIL-YY1 axis. Bioinformatic analyses will be performed to validate the axis. Both YY1 and SNAIL regulate PD-L1 expression and an immunosuppressive TME whereas RKIP expression reverses the immunosuppressive phenotype and facilitates GBM’s response to immunotherapy. Conclusions: The dysregulated RKIP-SNAIL-YY1 axis in GBM plays a pivotal role in the pathogenesis of GBM and resistance to current therapeutics and immunotherapy. Hence, targeting any of the gene products in the axis will negatively affect the other two gene products. Various means are proposed for targeting each gene product including small molecular inhibitors, mRNA and lncRNA, nanotechnology, PROTAC, etc. These need to be examined in preclinical models for effectiveness and toxicities as well as addressing various challenges for the specific and direct targeting of the cancer cells.

Immune checkpoint inhibitors (ICIs) have significantly improved survival rates for many types of cancer, giving patients survival prognoses that had been previously unattainable. Unfortunately, in many advanced cancers, including breast cancer (BC), objective response rates (ORRs) have been reported to be between 5% and 25% and immune-related adverse events (irAEs) can be severe, emphasizing the need to improve the effectiveness of ICIs while minimizing irAEs. In recent years, probiotics and various bacteria consortia have gained growing recognition for their application in immunotherapies for various cancers. Many preclinical models have demonstrated that probiotics significantly influence the gut microbiome, enhancing the production of beneficial metabolites and promoting interactions with cytotoxic T cells to amplify the antitumor effects of ICIs. For the treatment of HER2+ BC, current clinical trials have administered ICIs in combination with anti-HER2 agents (e.g., trastuzumab) to enhance treatment efficacy. Thus far, this combination has shown promising results, especially in patients with advanced PDL1-positive disease. However, as these trials are still ongoing, the efficacy of immune checkpoint blockade (ICB) therapy for HER2+ BCs remains inconclusive and requires further investigation. Thus, this review discusses the use of probiotics in ICB therapy, focusing on the potential role of probiotics in HER2+ BC response to ICIs, their underlying mechanisms and challenges.

Non-Hodgkin lymphoma (NHL) presents a complex therapeutic challenge due to its heterogeneous nature and the high incidence of relapse following initial treatment. As such, patients who are more susceptible to treatment resistance face a poor prognosis with limited treatment options. With recent advances, the direct targeting of overexpressed gene products is a novel therapeutic approach to overcome resistance mechanisms in unresponsive NHL patients. In the pathogenesis of NHL, we suspect aberrant deregulations amongst three major oncogenes: Yin Yang 1 (YY1), B-cell lymphoma 2 (Bcl-2), and Myelocytomatosis oncogene (c-Myc). Through analyses of the reported literature data, we have determined, indeed, multiple cross-talk signaling pathways (i.e. with factors MDM2, NF-κΒ, SENP1, TGF-β, p53, ERK) for YY1, Bcl-2, and c-Myc that enable malignant cells to evade immune surveillance, promote tumor aggressiveness, and maintain resistance against various treatment modalities. In addition, we also present various approaches and agents to target each of the gene products, with discussion of challenges faced to generate such agents that specifically target the tumor cells.

The interplay between probiotics and cancer development has emerged as a complex but important field in oncology research. While probiotics are known gut microbiome modulators and have the ability to modulate an immune response, their role in the prevention and treatment of cancer are inadequately understood. Evidence from peer-reviewed literature suggests that probiotics-mediated effects contribute to cancer prevention and treatment. Such effects include the enhancement of barrier function, production of anti-inflammatory agents, modulation of immune responses, and regulation of the tumor microenvironment. Clinical studies offer promising results in terms of therapeutic applications in certain cancers where probiotic bacteria may help reduce risk factors while enhancing treatment efficacy. Emerging evidence indicates potential benefits in the combination of probiotics with immunotherapy, including improved response rates and reduced side effects. Significant challenges remain, however, including the standardization of probiotic bacterial constituents, the route of administration, optimal delivery methods and safety concerns. Future research should focus on personalized treatment plans with emphasis on strain-specific effects and the development of next-generation probiotics specifically targeted for cancer applications, in combination with current treatment therapeutics.

We have recently witnessed several milestones in the treatment of a subset of cancer patients with immunotherapy and resulting in significant clinical responses. However, there is a subset that is unresponsive due to resistant factors in the cancer cells that are responsible for immune evasion. The characterization of such factors might lead to novel targeted therapies to restore the anti-tumor immunotherapies. We describe three dysregulated gene products, namely, Yin Yang1 (YY1), EZH2, and RKIP (PEBP1), that play pivotal roles in immune evasion. We report on the various molecular regulatory roles and signaling pathways that lead to the overexpression of YY1 and EZH2 and under expression of RKIP in cancer cells and established cross-talk signaling pathways amongst these three gene products. Such cross-talks established the dysregulated YY1-EZH2-RKIP axis and its pivotal role in the regulation of immune evasion. Thus, this axis is a potentially new therapeutic target to inhibit immune evasion by targeting the inhibition of YY1 or EZH2 or the induction of RKIP. Various agents are discussed to target each of these gene products, alone or in combination, to be investigated preclinically. However, the specific targeting to the tumor cells and sparing normal tissues is challenging, though new approaches are feasible.

The gut microbiota is integral to human health, influencing nutrition, metabolism, and immunity. Dysbiosis has been implicated in cancer development and resistance to therapies, highlighting the potential of microbiota modulation as a therapeutic strategy. Melanoma, while comprising only 1% of skin cancer diagnoses, accounts for over 80% of skin cancer related deaths, emphasizing the need for innovative approaches to enhance treatment efficacy. Although immune checkpoint inhibitors (ICIs) such as anti-programmed cell death protein (PD-1) and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) blockade therapies have significantly improved survival for some melanoma patients, the majority fails to achieve durable responses and often develops long-term resistance to these treatments. Fecal microbiota transplantation (FMT) is emerging as a promising intervention to restore microbial balance and enhance treatment efficacy. This review explores the historical evolution and current applications of FMT in oncology, with a focus on its ability to modulate the gut microbiome, augment antitumor immunity, and overcome resistance to checkpoint blockade therapy in melanoma. Despite its promise, significant challenges remain, including ensuring the safety of the procedure, selecting suitable donors, and addressing regulatory hurdles. Future research aimed at optimizing FMT protocols, identifying key microbial strains, and understanding the mechanisms underlying microbiota-immune interactions will be essential to fully harness the potential of FMT as a transformative adjunct in cancer treatment.

Innovations in cancer immunotherapy have resulted in the development of several novel immunotherapeutic strategies that can disrupt immunosuppression. One key advancement lies in immune checkpoint inhibitors (ICIs), which have shown significant clinical efficacy and increased survival rates in patients with various therapy-resistant cancers. This immune intervention consists of monoclonal antibodies directed against inhibitory receptors (e.g., PD-1) on cytotoxic CD8 T cells or against corresponding ligands (e.g., PD-L1/PD-L2) overexpressed on cancer cells and other cells in the tumor microenvironment (TME). However, not all cancer cells respond—there are still poor clinical responses, immune-related adverse effects, adaptive resistance, and vulnerability to ICIs in a subset of patients with cancer. This challenge showcases the heterogeneity of cancer, emphasizing the existence of additional immunoregulatory mechanisms in many patients. Therefore, it is essential to investigate PD-L1’s interaction with other oncogenic genes and pathways to further advance targeted therapies and address resistance mechanisms. Accordingly, our aim was to investigate the mechanisms governing PD-L1 expression in tumor cells, given its correlation with immune evasion, to uncover novel mechanisms for decreasing PD-L1 expression and restoring anti-tumor immune responses. Numerous studies have demonstrated that the upregulation of Raf Kinase Inhibitor Protein (RKIP) in many cancers contributes to the suppression of key hyperactive pathways observed in malignant cells, alongside its broadening involvement in immune responses and the modulation of the TME. We, therefore, hypothesized that the role of PD-L1 in cancer immune surveillance may be inversely correlated with the low expression level of the tumor suppressor Raf Kinase Inhibitor Protein (RKIP) expression in cancer cells. This hypothesis was investigated and we found several signaling cross-talk pathways between the regulations of both RKIP and PD-L1 expressions. These pathways and regulatory factors include the MAPK and JAK/STAT pathways, GSK3β, cytokines IFN-γ and IL-1β, Sox2, and transcription factors YY1 and NFκB. The pathways that upregulated PD-L1 were inhibitory for RKIP expression and vice versa. Bioinformatic analyses in various human cancers demonstrated the inverse relationship between PD-L1 and RKIP expressions and their prognostic roles. Therefore, we suspect that the direct upregulation of RKIP and/or the use of targeted RKIP inducers in combination with ICIs could result in a more targeted anti-tumor immune response—addressing the therapeutic challenges related to PD-1/PD-L1 monotherapy alone.

Recent advancements in cancer treatment have explored a variety of approaches to address the needs of patients. Recently, immunotherapy has evolved as an efficacious treatment for various cancers resistant to conventional therapies. Hence, significant milestones in immunotherapy were achieved clinically in a large subset of cancer patients. Unfortunately, some cancer types do not respond to treatment, and among the responsive cancers, some patients remain unresponsive to treatment. Consequently, there is a critical need to examine the mechanisms of immune resistance and devise strategies to target immune suppressor cells or factors, thereby allowing for tumor sensitivity to immune cytotoxic cells. M2 macrophages, also known as tumor-associated macrophages (TAMs), are of interest due to their role in suppressing the immune system and influencing antitumor immune responses through modulating T cell activity and immune checkpoint expression. TAMs are associated with signaling pathways that modulate the tumor microenvironment (TME), contributing to immune evasion. One approach targets TAMs, focusing on preventing the polarization of M1 macrophages into the protumoral M2 phenotype. Other strategies focus on direct or indirect targeting of M2 macrophages through understanding the interaction of TAMs with immune factors or signaling pathways. Clinically, biomarkers associated with TAMs' immune resistance in cancer patients have been identified, opening avenues for intervention using pharmacological agents or immunotherapeutic approaches. Ultimately, these multifaceted approaches are promising in overcoming immune resistance and improving cancer treatment outcomes.

During the last decade, we have witnessed several milestones in the treatment of various resistant cancers including immunotherapeutic strategies that have proven to be superior to conventional treatment options, such as chemotherapy and radiation. This approach utilizes the host's immune response, which is triggered by cancer cells expressing tumor-associated antigens or neoantigens. The responsive immune cytotoxic CD8+ T cells specifically target and kill tumor cells, leading to tumor regression and prolongation of survival in some cancers; however, some cancers may exhibit resistance due to the inactivation of anti-tumor CD8+ T cells. One mechanism by which the anti-tumor CD8+ T cells become dysfunctional is through the activation of the inhibitory receptor programmed death-1 (PD-1) by the corresponding tumor cells (or other cells in the tumor microenvironment (TME)) that express the programmed death ligand-1 (PD-L1). Hence, blocking the PD-1/PD-L1 interaction via specific monoclonal antibodies (mAbs) restores the CD8+ T cells' functions, leading to tumor regression. Accordingly, the Food and Drug Administration (FDA) has approved several checkpoint antibodies which act as immune checkpoint inhibitors. Their clinical use in various resistant cancers, such as metastatic melanoma and non-small-cell lung cancer (NSCLC), has shown significant clinical responses. We have investigated an alternative approach to prevent the expression of PD-L1 on tumor cells, through targeting the oncogenic transcription factor Yin Yang 1 (YY1), a known factor overexpressed in many cancers. We report the regulation of PD-L1 by YY1 at the transcriptional, post-transcriptional, and post-translational levels, resulting in the restoration of CD8+ T cells' anti-tumor functions. We have performed bioinformatic analyses to further explore the relationship between both YY1 and PD-L1 in cancer and to corroborate these findings. In addition to its regulation of PD-L1, YY1 has several other anti-cancer activities, such as the regulation of proliferation and cell viability, invasion, epithelial-mesenchymal transition (EMT), metastasis, and chemo-immuno-resistance. Thus, targeting YY1 will have a multitude of anti-tumor activities resulting in a significant obliteration of cancer oncogenic activities. Various strategies are proposed to selectively target YY1 in human cancers and present a promising novel therapeutic approach for treating unresponsive cancer phenotypes. These findings underscore the distinct regulatory roles of YY1 and PD-L1 (CD274) in cancer progression and therapeutic response.

We have witnessed the emergence of immunotherapy against various cancers that resulted in significant clinical responses and particularly in cancers that were resistant to chemotherapy. These milestones have ignited the development of novel strategies to boost the anti-tumor immune response for immune-suppressed tumors in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are the most abundant cells in the TME, and their frequency correlates with poor prognosis. Hence, several approaches have been developed to target TAMs in effort to restore the anti-tumor immune response and inhibit tumor growth and metastasis. One approach discussed herein is targeting TAMs via their depletion. Several methods have been reported for TAMs depletion including micro-RNAs, transcription factors (e.g., PPARγ, KLF4, STAT3, STAT6, NF-κB), chemokines and chemokine receptors, antibodies-mediated blocking the CSF-1/CSF-1R pathway, nanotechnology, and various combination treatments. In addition, various clinical trials are currently examining the targeting of TAMs. Many of these methods also have side effects that need to be monitored and reduced. Future perspectives and directions are discussed.

Tumor-associated macrophages (TAMs) are the predominant cell infiltrate in the immunosuppressive tumor microenvironment (TME). TAMs are central to fostering pro-inflammatory conditions, tumor growth, metastasis, and inhibiting therapy responses. Many cancer patients are innately refractory to chemotherapy and or develop resistance following initial treatments. There is a clinical correlation between the level of TAMs in the TME and chemoresistance. Hence, the pivotal role of TAMs in contributing to chemoresistance has garnered significant attention toward targeting TAMs to reverse this resistance. A prerequisite for such an approach requires a thorough understanding of the various underlying mechanisms by which TAMs inhibit response to chemotherapeutic drugs. Such mechanisms include enhancing drug efflux, regulating drug metabolism and detoxification, supporting cancer stem cell (CSCs) resistance, promoting epithelial-mesenchymal transition (EMT), inhibiting drug penetration and its metabolism, stimulating angiogenesis, impacting inhibitory STAT3/NF-κB survival pathways, and releasing specific inhibitory cytokines including TGF-β and IL-10. Accordingly, several strategies have been developed to overcome TAM-modulated chemoresistance. These include novel therapies that aim to deplete TAMs, repolarize them toward the anti-tumor M1-like phenotype, or block recruitment of monocytes into the TME. Current results from TAM-targeted treatments have been unimpressive; however, the use of TAM-targeted therapies in combination appears promising These include targeting TAMs with radiotherapy, chemotherapy, chemokine receptor inhibitors, immunotherapy, and loaded nanoparticles. The clinical limitations of these strategies are discussed.

We have witnessed in the last decade new milestones in the treatment of various resistant cancers with new immunotherapeutic modalities. These advances have resulted in significant objective durable clinical responses in a subset of cancer patients. These findings strongly suggested that immunotherapy should be considered for the treatment of all subsets of cancer patients. Accordingly, the mechanisms underlying resistance to immunotherapy must be explored and develop new means to target these resistant factors. One of the pivotal resistance mechanisms in the tumor microenvironment (TME) is the high infiltration of tumor-associated macrophages (TAMs) that are highly immunosuppressive and responsible, in large part, of cancer immune evasion. Thus, various approaches have been investigated to target the TAMs to restore the anti-tumor immune response. One approach is to polarize the M2 TAMS to the M1 phenotype that participates in the activation of the anti-tumor response. In this review, we discuss the various and differential properties of the M1 and M2 phenotypes, the molecular signaling pathways that participate in the polarization, and various approaches used to target the polarization of the M2 TAMs into the M1 anti-tumor phenotype. These approaches include inhibitors of histone deacetylases, PI3K inhibitors, STAT3 inhibitors, TLR agonists, and metabolic reprogramming. Clearly, due to the distinct features of various cancers and their heterogeneities, a single approach outlined above might only be effective against some cancers and not others. In addition, targeting by itself may not be efficacious unless used in combination with other therapeutic modalities.

Untreated primary carcinomas often lead to progression, invasion and metastasis, a process that involves the epithelial-to-mesenchymal transition (EMT). Several transcription factors (TFs) mediate the development of EMT, including SNAIL1/SNAIL2, TWIST1/TWIST2 and ZEB1/ZEB2, which are overexpressed in various carcinomas along with the under expression of the metastasis suppressor Raf Kinase Inhibitor Protein (RKIP). Overexpression of RKIP inhibits EMT and the above associated TFs. We, therefore, hypothesized that there are inhibitory cross-talk signaling pathways between RKIP and these TFs. Accordingly, we analyzed the various properties and biomarkers associated with the epithelial and mesenchymal tissues and the various molecular signaling pathways that trigger the EMT phenotype such as the TGF-β, the RTK and the Wnt pathways. We also presented the various functions and the transcriptional, post-transcriptional and epigenetic regulations for the expression of each of the EMT TFs. Likewise, we describe the transcriptional, post-transcriptional and epigenetic regulations of RKIP expression. Various signaling pathways mediated by RKIP, including the Raf/MEK/ERK pathway, inhibit the TFs associated with EMT and the stabilization of epithelial E-Cadherin expression. The inverse relationship between RKIP and the TF expressions and the cross-talks were further analyzed by bioinformatic analysis. High mRNA levels of RKIP correlated negatively with those of SNAIL1, SNAIL2, TWIST1, TWIST2, ZEB1, and ZEB2 in several but not all carcinomas. However, in these carcinomas, high levels of RKIP were associated with good prognosis, whereas high levels of the above transcription factors were associated with poor prognosis. Based on the inverse relationship between RKIP and EMT TFs, it is postulated that the expression level of RKIP in various carcinomas is clinically relevant as both a prognostic and diagnostic biomarker. In addition, targeting RKIP induction by agonists, gene therapy and immunotherapy will result not only in the inhibition of EMT and metastases in carcinomas, but also in the inhibition of tumor growth and reversal of resistance to various therapeutic strategies. However, such targeting strategies must be better investigated as a result of tumor heterogeneities and inherent resistance and should be better adapted as personalized medicine.