Analysis of PI3K pathway components in human cancers

Targeting the PI3K/AKT signaling pathway in anticancer research: a recent update on inhibitor design and clinical trials (2020-2023)

INTRODUCTION

Recent years have witnessed great achievements in drug design and development targeting the phosphatidylinositol 3-kinase/protein kinase-B (PI3K/AKT) signaling pathway, a pathway central to cell growth and proliferation. The nearest neighbor protein-protein interaction networks for PI3K and AKT show the interplays between these target proteins which can be harnessed for drug discovery. In this review, we discuss the drug design and clinical development of inhibitors of PI3K/AKT in the past three years. We review in detail the structures, selectivity, efficacy, and combination therapy of 35 inhibitors targeting these proteins, classified based on the target proteins. Approaches to overcoming drug resistance and to minimizing toxicities are discussed. Future research directions for developing combinational therapy and PROTACs of PI3K and AKT inhibitors are also discussed.

AREA COVERED

This review covers clinical trial reports and patent literature on inhibitors of PI3K and AKT published between 2020 and 2023.

EXPERT OPINION

To address drug resistance and drug toxicity of inhibitors of PI3K and AKT, it is highly desirable to design and develop subtype-selective PI3K inhibitors or subtype-selective AKT1 inhibitors to minimize toxicity or to develop allosteric drugs that can form covalent bonds. The development of PROTACs of PI3Kα or AKT helps to reduce off-target toxicities.

The combined effect and mechanism of antiangiogenic drugs and PD-L1 inhibitor on cell apoptosis in triple negative breast cancer

Background

Breast cancer is the most common cancer worldwide, and triple-negative breast cancer (TNBC) has the worst prognosis. Standard systemic treatment includes chemotherapy and immunotherapy. Poly ADP-ribose polymerase (PARP) inhibitors are considered in breast cancer (BRCA) susceptibility genes mutated tumors. The role of antiangiogenic drugs is controversial. Immunotherapy with immune checkpoint inhibitor is now a standard of care for TNBC in the US, but its use in combination with anlotinib, an inhibitor of angiogenesis, on TNBC cells was never investigated.

Methods

We tested the effects of anlotinib and programmed cell death-ligand 1 (PD-L1) inhibitor on the proliferation, apoptosis, migration, and invasion of MDA-MB-468 and BT-549 TNBC cells through 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assays, cell apoptosis assay, wound healing and transwell matrix assays, and verified whether the combination of the two drugs had synergistic effect. Western blotting was used to detect the effect of anlotinib and PD-L1 inhibitor on the protein expression levels of PI3K, p-PI3K, AKT, p-AKT, Bcl-xl in MDA-MB-468 and BT-549 cells. The effects of anlotinib, PD-L1 inhibitor and the combination of the two drugs on the transplanted tumor of TNBC mice were tested by animal experiments.

Results

Anlotinib and PD-L1 inhibitor inhibited the proliferation and promote cell apoptosis of MDA-MB-468 and BT-549 cells, and the combination demonstrated the synergetic effect. Anlotinib and PD-L1 inhibitor inhibited cell migration and invasion, and the effect was strongest in the combination group. Both anlotinib and PD-L1 inhibitor reduced the expression of p-PI3K, p-AKT and Bcl-xl proteins in cells and the effects were the strongest in the combination group. Both anlotinib and PD-L1 inhibitor inhibited the growth of transplanted tumors in mice, and the combined group demonstrated the strongest growth suppression.

Conclusions

Anlotinib and PD-L1 inhibitor can inhibit cell proliferation, migration, and invasion of TNBC and promote cell apoptosis, and the two drugs show combined anti-tumor effects in vivo and in vitro. The combination of anlotinib and PD-L1 inhibitor may promote apoptosis of TNBC cells through PI3K/AKT/Bcl-xl signaling pathways, which might offer potential clinical treatment roles for these.

Role of alternatively spliced, pro‐survival Protein Kinase C delta VIII (PKCδVIII) in ovarian cancer

Ovarian cancer is the deadliest malignant disease in women. Protein Kinase C delta (PRKCD; PKCδ) is serine/threonine kinase extensively linked to various cancers. In humans, PKCδ is alternatively spliced to PKCδI and PKCδVIII. However, the specific function of PKCδ splice variants in ovarian cancer has not been elucidated yet. Hence, we evaluated their expression in human ovarian cancer cell lines (OCC): SKOV3 and TOV112D, along with the normal T80 ovarian cells. Our results demonstrate a marked increase in PKCδVIII in OCC compared to normal ovarian cells. Therefore, we elucidated the role of PKCδVIII and the underlying mechanism of its expression in OCC. Using overexpression and knockdown studies, we demonstrate that PKCδVIII increases cellular survival and migration in OCC. Further, overexpression of PKCδVIII in T80 cells resulted in increased expression of Bcl2 and knockdown of PKCδVIII in OCC decreased Bcl2 expression. Using co‐immunoprecipitations and immunocytochemistry, we demonstrate nuclear localization of PKCδVIII in OCC and further show increased association of PKCδVIII with Bcl2 and Bcl‐xL in OCC. Using PKCδ splicing minigene, mutagenesis, siRNA and antisense oligonucleotides, we demonstrate that increased levels of alternatively spliced PKCδVIII in OCC is regulated by splice factor SRSF2. Finally, we verified that PKCδVIII levels are elevated in samples of human ovarian cancer tissue. The data presented here demonstrate that the alternatively spliced, signaling kinase PKCδVIII is a viable target to develop therapeutics to combat progression of ovarian cancer.

Apatinib enhances the anti-tumor effect of paclitaxel via the PI3K/p65/Bcl-xl pathway in triple-negative breast cancer

Background

Apatinib is a new generation of small molecule tyrosine kinase inhibitor, which can highly selectively inhibit phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR-2). This study aimed to investigate the synergistic effects of apatinib and paclitaxel (PTX) on triple-negative breast cancer (TNBC) in vivo and in vitro, and to explore the molecular mechanism of the PI3K/p65/Bcl-xl pathway.

Methods

In vitro, 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) method, flow cytometry (FCM), wound healing assay, and transwell matrix assay were conducted to measure the effects of apatinib and PTX on cell viability, apoptosis, migration, and invasion in TNBC cell line MDA-MB-468. Western blot (WB) was conducted to detect protein expression levels of PI3K, p65, and Bcl-xl after the application of apatinib and PTX. In vivo, MDA-MB-468 tumor-bearing nude mice were treated with apatinib and PTX, and tumor growth was observed.

Results

In vitro, apatinib and PTX could synergistically suppress the cell viability, the combined group had the most obvious effect. Apatinib and PTX could promote apoptosis and suppress migration and invasion of TNBC cells. Apatinib could reduce the expression of p-PI3K, p65, and Bcl-xl proteins (P<0.05). In vivo, apatinib and PTX could inhibit tumor size and weight of model mice, and the combined agents had a more significant effect.

Conclusions

Apatinib could enhance the anti-tumor effect of PTX on TNBC cells through the PI3K/p65/Bcl-xl molecular pathway, and apatinib combined with PTX might be a promising option for TNBC treatment.

A balance score between immune stimulatory and suppressive microenvironments identifies mediators of tumour immunity and predicts pan-cancer survival

BACKGROUND

The balance between immune-stimulatory and immune-suppressive mechanisms in the tumour microenvironment is associated with tumour rejection and can predict the efficacy of immune checkpoint-inhibition therapies.

METHODS

We consider the observed differences between the transcriptional programmes associated with cancer types where the levels of immune infiltration predict a favourable prognosis versus those in which the immune infiltration predicts an unfavourable prognosis and defined a score named Mediators of Immune Response Against Cancer in soLid microEnvironments (MIRACLE). MIRACLE deconvolves T cell infiltration, from inhibitory mechanisms, such as TGFβ, EMT and PI3Kγ signatures.

RESULTS

Our score outperforms current state-of-the-art immune signatures as a predictive marker of survival in TCGA (n = 9305, HR: 0.043, p value: 6.7 × 10^-36). In a validation cohort (n = 7623), MIRACLE predicts better survival compared to other immune metrics (HR: 0.1985, p value: 2.73 × 10^-38). MIRACLE also predicts response to checkpoint-inhibitor therapies (n = 333). The tumour-intrinsic factors inversely associated with the reported score such as EGFR, PRKAR1A and MAP3K1 are frequently associated with immune-suppressive phenotypes.

CONCLUSIONS

The association of cancer outcome with the level of infiltrating immune cells is mediated by the balance of activatory and suppressive factors. MIRACLE accounts for this balance and predicts favourable cancer outcomes.

Persistent Rheb-induced mTORC1 activation in spinal cord neurons induces hypersensitivity in neuropathic pain

The small GTPase Ras homolog enriched in the brain (Rheb) can activate mammalian target of rapamycin (mTOR) and regulate the growth and cell cycle progression. We investigated the role of Rheb-mediated mTORC1 signaling in neuropathic pain. A chronic constriction injury (CCI) model was dopted. CCI induced obvious spinal Rheb expression and phosphorylation of mTOR, S6, and 4-E-BP1. Blocking mTORC1 signal with rapamycin alleviated the neuropathic pain and restored morphine efficacy in CCI model. Immunofluoresence showed a neuronal co-localization of CCI-induced Rheb and pS6. Rheb knockin mouse showed a similar behavioral phenotype as CCI. In spinal slice recording, CCI increased the firing frequency of neurons expressing HCN channels; inhibition of mTORC1 with rapamycin could reverse the increased spinal neuronal activity in neuropathic pain. Spinal Rheb is induced in neuropathic pain, which in turn active the mTORC1 signaling in CCI. Spinal Rheb-mTOR signal plays an important role in regulation of spinal sensitization in neuropathic pain, and targeting mTOR may give a new strategy for pain management.

The Biological Role of Sponge Circular RNAs in Gastric Cancer: Main Players or Coadjuvants?

Circular RNAs (circRNAs) are a new class of long noncoding RNAs able to perform multiple functions, including sponging microRNAs (miRNAs) and RNA-Binding Proteins (RBPs). They play an important role in gastric carcinogenesis, but its involvement during gastric cancer (GC) development and progression are not well understood. We gathered miRNA and/or RBPs sponge circRNAs present in GC, and accessed their biological roles through functional enrichment of their target genes or ligand RBPs. We identified 54 sponge circRNAs in GC that are able to sponge 51 miRNAs and 103 RBPs. Then, we evaluated their host gene expression using The Cancer Genome Atlas (TCGA) database and observed that COL1A2 is the most overexpressed gene, which may be due to circHIPK3/miR-29b-c/COL1A2 axis dysregulation. We identified 27 GC-related pathways that may be affected mainly by circPVT1, circHIPK3 and circNF1. Our results indicate that circHIPK3/miR-107/BDNF/LIN28 axis may mediate chemoresistance in GC, and that circPVT1, circHIPK3, circNF1, ciRS-7 and circ_0000096 appear to be involved in gastrointestinal cancer development. Lastly, circHIPK3, circNRIP1 and circSMARCA5 were identified in different ethnic populations and may be ubiquitous modulators of gastric carcinogenesis. Overall, the studied sponge circRNAs are part of a complex RBP-circRNA-miRNA-mRNA interaction network, and are involved in the establishment, chemoresistance and progression of GC.

Simultaneous targeting of HER family pro-survival signaling with Pan-HER antibody mixture is highly effective in TNBC: a preclinical trial with PDXs

BACKGROUND

The human epidermal growth factor receptor (HER) family, notably EGFR, is overexpressed in most triple-negative breast cancer (TNBC) cases and provides cancer cells with compensatory signals that greatly contribute to the survival and development of resistance in response to therapy. This study investigated the effects of Pan-HER (Symphogen, Ballerup, Denmark), a novel mixture of six monoclonal antibodies directed against members of the HER family EGFR, HER2, and HER3, in a preclinical trial of TNBC patient-derived xenografts (PDXs).

METHODS

Fifteen low passage TNBC PDX tumor samples were transferred into the right mammary fat pad of mice for engraftment. When tumors reached an average size of 100-200 mm3, mice were randomized (n ≥ 6 per group) and treated following three 1-week cycles consisting of three times/week intraperitoneal (IP) injection of either formulation buffer (vehicle control) or Pan-HER (50 mg/kg). At the end of treatment, tumors were collected for Western blot, RNA, and immunohistochemistry analyses.

RESULTS

All 15 TNBC PDXs were responsive to Pan-HER treatment, showing significant reductions in tumor growth consistent with Pan-HER-mediated tumor downmodulation of EGFR and HER3 protein levels and significantly decreased activation of associated HER family signaling pathways AKT and ERK. Tumor regression was observed in five of the models, which corresponded to those PDX tumor models with the highest level of HER family activation.

CONCLUSIONS

The marked effect of Pan-HER in numerous HER family-dependent TNBC PDX models justifies further studies of Pan-HER in TNBC clinical trials as a potential therapeutic option.

Status of Immune Oncology: Challenges and Opportunities

This volume is intended to review the methods used to identify biomarkers predictive of cancer responsiveness to immunotherapy. The successful development of clinically actionable biomarkers depends upon three features: (a) their biological role with respect to malignant transformation and tumor progression; (b) the ability to detect them with robust, reliable, and clinically applicable assays; and (c) their prognostic or predictive value, as validated in clinical trials.Identifying biomarkers that have predictive value for patient selection based on the likelihood of benefiting from anticancer immunotherapy is a lengthy and complex process. To date, few predictive biomarkers for anticancer immunotherapy have been robustly analytically and clinically validated (i.e., PD-L1 expression as measured by IHC assays and microsatellite instability (MSI)/dMMR as measured by PCR or IHC, respectively).This introductory chapter to this book focuses on scientific and technical aspects relevant to the identification and validation of predictive biomarkers for immunotherapy. We emphasize that methods should address both the biology of the tumor and the tumor microenvironment. Moreover, the identification of biomarkers requires highly sensitive, multiplexed, comprehensive techniques, especially for application in clinical care. Thus, in this chapter, we will define the outstanding questions related to the immune biology of cancer as a base for development of the biomarkers and assays using diverse methodologies. These biomarkers will likely be identified through research that integrates conventional immunological approaches along with high-throughput genomic and proteomic screening and the host immune response of individual patients that relates to individual tumor biology and immune drugs' mechanism of action.Checkpoint inhibitor therapy (CIT) is by now an accepted modality of cancer treatment. However, immune resistance is common, and most patients do not benefit from the treatment. The reasons for resistance are diverse, and approaches to circumvent it need to consider genetic, biologic, and environmental factors that affect anticancer immune response. Here, we propose to systematically address fundamental concepts based on the premise that malignant cells orchestrate their surroundings by interacting with innate and adaptive immune sensors. This principle applies to most cancers and governs their evolution in the immune-competent host. Understanding the basic requirement(s) for this evolutionary process will guide biomarker discovery and validation and ultimately guide to effective therapeutic choices. This volume will also discuss novel biomarker approaches aimed at informing an effective assay development from a mechanistic point of view, as well as the clinical implementation (i.e., patient enrichment) for immune therapies.

The Paradox of Cancer Immune Exclusion: Immune Oncology Next Frontier

Checkpoint inhibitor therapy (CIT) has revolutionized cancer treatment but it has also reached a standstill when an absent dialog between cancer and immune cells makes it irrelevant. This occurs with high prevalence in the context of "immune silent" and, even perhaps, "immune-excluded" tumors. The latter are characterized by T cells restricted to the periphery of cancer nests. Since in either case T cells do not come in direct contact with most cancer cells, CIT rests immaterial. Adoptive cell therapy (ACT), may also be affected by limited access to antigen-bearing cancer cells. While lack of immunogenicity intuitively explains the immune silent phenotype, immune exclusion is perplexing. The presence of T cells at the periphery suggests that chemo-attraction recruits them and an immunogenic stimulus promotes their persistence. However, what stops the T cells from infiltrating the tumors' nests and reaching the germinal center (GC)? Possibly, a concentric gradient of increased chemo-repulsion or decreased chemo-attraction demarcates an abrupt "do not trespass" warning. Various hypotheses suggest physical or functional barriers but no definitive consensus exists over the weight that each plays in human cancers. On one hand, it could be hypothesized that the intrinsic biology of cancer cells may degenerate from a "cancer stem cell" (CSC)-like phenotype in the GC toward a progressively more immunogenic phenotype prone to immunogenic cell death (ICD) at the periphery. On the other hand, the intrinsic biology of the cancer cells may not change but it is the disorderly architecture of the tumor microenvironment (TME) that alters in a centripetal direction cancer cell metabolism, both directly and indirectly, the function of surrounding stromal cells. In this chapter, we examine whether the paradoxical exclusion of T cells from tumors may serve as a model to understand the requirements for tumor immune infiltration and, correspondingly, we put forth strategies to restore the dialog between immune cells and cancer to enhance the effectiveness of immune oncology (IO) approaches.

Integrin alpha 7 correlates with poor clinical outcomes, and it regulates cell proliferation, apoptosis and stemness via PTK2-PI3K-Akt signaling pathway in hepatocellular carcinoma

This study aimed to evaluate the correlation of integrin alpha 7 (ITGA7) with clinical outcomes and its effect on cell activities as well as stemness in hepatocellular carcinoma (HCC). HCC tumor tissues and paired adjacent tissues from 90 HCC patients were obtained and ITGA7 expression was detected using immunohistochemistry assay. Cellular experiments were conducted to examine the effect of ITGA7 on cell activities, astemness via ITGA7 ShRNA transfection, and compensation experiments were further performed to test whether ITGA7 functioned via regulating PTK2-PI3K-AKT signaling pathway. ITGA7 was overexpressed in tumor tissues compared with paired adjacent tissues and its high expression was correlated with larger tumor size, vein invasion and advanced Barcelona Clinic Liver Cancer stage, and it also independently predicted worse overall survival in HCC patients. In cellular experiments, ITGA7 was upregulated in SMMC-7721, Hep G2, HuH-7 and BEL-7404 cell lines compared with normal human liver cells HL-7702. ITGA7 knockdown suppressed cell proliferation but promoted apoptosis, and it also downregulated CSCs markers (CD44, CD133 and OCT-4) as well as PTK2, PI3K and AKT expressions in SMMC-7721 and Hep G2 cell lines. ITGA7 overexpression promoted cell proliferation but inhibited apoptosis, and it also upregulated CSCs markers in HL-7702 cells. Further compensation experiments verified that ITGA7 regulated cell proliferation, apoptosis and CSCs markers via PTK2-PI3K-Akt signaling pathway. ITGA7 negatively associates with clinical outcomes in HCC patients, and it regulates cell proliferation, apoptosis and CSCs markers via PTK2-PI3K-Akt signaling pathway.

Altered CSF Proteomic Profiling of Paediatric Acute Lymphocytic Leukemia Patients with CNS Infiltration

Background

For childhood acute lymphocytic leukemia (ALL), central nervous system leukemia (CNSL) is still the main reason of treatment failure. Changes of cerebrospinal fluid (CSF) proteome are deemed to occur after intrathecal chemotherapy.

Objective

To find critical CSF biomarkers, which could be utilized to increase diagnostic and prognostic accuracy of CNSL.

Methods

We performed proteomic profiling of CSF before and after the treatment of six sporadic paediatric patients diagnosed as ALL with central nervous system (CNS) involvement. CSF samples were properly processed and analyzed through the use of label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Results

Among identified 428 unique proteins in all CSF samples, we quantified 10 altered proteins with diverse biological functions after induction chemotherapy.

Conclusions

The levels of those 10 proteins change during the treatment of CNSL. Some of the proteins are likely to play a vital biological role as biomarkers for the development of ALL. In addition, our results indicated the feasible and reproducible utility of CSF for diagnosis and prognosis of patients with CNSL.

Long noncoding RNA HULC accelerates liver cancer by inhibiting PTEN via autophagy cooperation to miR15a

BACKGROUND

Long noncoding RNA HULC is highly up-regulation in human hepatocellular carcinoma (HCC). However, the functions of HULC in hepatocarcinogenesis remains unclear.

METHODS

RT-PCR, Western blotting, Chromatin immunoprecipitation (CHIP) assay, RNA Immunoprecipitation (RIP) and tumorignesis test in vitro and in vivo were performed.

RESULTS

HULC is negatively associated with expression of PTEN or miR15a in patients of human liver cancer. Moreover, HULC accelerates malignant progression of liver cancer cells in vitro and in vivo. Mechanistically, HULC increasesthe expression of P62 via decreasing mature miR15a. On the other hand, excessive HULC increases the expression of LC3 on the level of transcription and then activates LC3 through Sirt1 (a deacetylase). Notably, HULC enhanced the interplay between LC3 and ATG3. Furthermore, HULC also increases the expression of becline-1(autophagy related gene). Therefore, HULC increases the cellular autophagy by increasing LC3II dependent on Sirt1.Noteworthy, excessive HULC reduces the expression of PTEN, β-catenin and enhances the expression of SAPK/JUNK, PKM2, CDK2, NOTCH1, C-Jun in liver cancer cells. Of significance, our observations also revealed that HULC inhibited PTEN through ubiquitin-proteasome system mediated by autophagy-P62.Ultimately,HULC activates AKT-PI3K-mTOR pathway through inhibiting PTEN in human liver cancer cells.

CONCLUSIONS

This study elucidates a novel mechanism that lncRNA HULC produces a vital function during hepatocarcinogenesis.

Immune oncology, immune responsiveness and the theory of everything

Anti-cancer immunotherapy is encountering its own checkpoint. Responses are dramatic and long lasting but occur in a subset of tumors and are largely dependent upon the pre-existing immune contexture of individual cancers. Available data suggest that three landscapes best define the cancer microenvironment: immune-active, immune-deserted and immune-excluded. This trichotomy is observable across most solid tumors (although the frequency of each landscape varies depending on tumor tissue of origin) and is associated with cancer prognosis and response to checkpoint inhibitor therapy (CIT). Various gene signatures (e.g. Immunological Constant of Rejection - ICR and Tumor Inflammation Signature - TIS) that delineate these landscapes have been described by different groups. In an effort to explain the mechanisms of cancer immune responsiveness or resistance to CIT, several models have been proposed that are loosely associated with the three landscapes. Here, we propose a strategy to integrate compelling data from various paradigms into a “Theory of Everything”. Founded upon this unified theory, we also propose the creation of a task force led by the Society for Immunotherapy of Cancer (SITC) aimed at systematically addressing salient questions relevant to cancer immune responsiveness and immune evasion. This multidisciplinary effort will encompass aspects of genetics, tumor cell biology, and immunology that are pertinent to the understanding of this multifaceted problem.

Evidence for the Involvement of COX-2/VEGF and PTEN/Pl3K/AKT Pathway the Mechanism of Oroxin B Treated Liver Cancer

Background

Oroxin B (OB) is one of flavonoids isolated from traditional Chinese herbal medicine Oroxylum indicum (L.) Vent. Recent studies suggest that flavonoids have obvious anti-liver tumors effect, but the precise molecular mechanism is still unclear.

Objective

The current study was performed to investigate the antitumor effects of OB on human hepatoma cell line SMMC-772 and explore the part of molecular mechanisms in this process.

Materials and Methods

MTT method, terminal deoxynucleotidyl transferase dUTP nick end labeling assay and flow cytometry were utilized to detect the inhibition of proliferation and the apoptosis after treating OB in of SMMC-7721 cells. The mRNA and proteins expressions of COX-2, vascular endothelial growth factor (VEGF), phosphatidylinositol-3-kinase (PI3K), p-AKT, and PTEN were measured by a real-time polymerase chain reaction and Western Blot method.

Results

The results showed that OB inhibited proliferation of SMMC-7721 cell in a dose-dependent manner, and induced its apoptosis. Moreover, OB unregulated PTEN and downregulated COX-2, VEGF, p-AKT, and PI3K.

Conclusion

Our results demonstrated that OB significantly inhibits proliferation and induce apoptosis, which may be strongly associated with the inhibiting COX-2/VEGF and PTEN/PI3K/AKT pathway signaling pathway in SMMC-7721 cells, OB potentially be used as a novel therapeutic agent for liver cancer.

SUMMARY

OB (Oroxin B) is one of the effective flavonoid components of traditional Chinese medicine O. indicum (L.)OB can inhibite the proliferation and promoted apoptosis of the human hepatoma cell line SMMC 7721OB plays a role of antitumor effect may to regulate COX 2/VEGF and PTEN/PI3K/AKT pathways directly or indirectly. Abbreviations used: OB: Oroxin B; MTT: 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide; COX-2: cyclooxygenase-2; PI3K: phosphatidylinositol 3 kinase; PTEN: Phosphatase and tensin homolog deleted on chromosome ten; VEGF: Vascular endothelial growth factor; RT-PCR: Reverse transcription polymerase chain reaction; DAPI: Diamidino 2 phenylindole; PBS: Phosphate buffer saline; FITC: Fluorescein isothiocyanate; PI: Propidium Iodide; RIPA: Radio immunoprecipitation assay lysis buffer; PMSF: Phenylmethanesulfonyl fluoride; PAGE: Polyacrylamide gel electrophoresis.

Cancer immune resistance: can theories converge?

Immune oncology (IO) is challenged to expand its usefulness to a broader range of cancers. A second generation of IO agents acting beyond the realm of Checkpoint Inhibitor Therapy (CIT) is sought with the intent of turning immune-resistant cancers into appealing IO targets. The published literature proposes a profusion of models to explain cancer immune resistance to CIT that largely outnumber the immune landscapes and corresponding resistance mechanisms. In spite of the complex and contradicting models suggested to explain refractoriness to CIT, the identification of prevailing mechanisms and their targeting may not be as daunting as it at first appears. Here, we suggest that cancer cells go through a conserved evolutionary bottleneck facing a Two-Option Choice to evade recognition by the immune competent host: they can either adopt a clean oncogenic process devoid of immunogenic stimuli (immune-silent tumors) or display an entropic biology prone to immune recognition (immune-active tumors) but resilient to rejection thanks to the recruitment of compensatory immune suppressive processes. Strategies aimed at enhancing the effectiveness of CIT will be different according to the immune landscape targeted.