Targeting Met and VEGFR Axis in Metastatic Castration-Resistant Prostate Cancer: ‘Game Over’?

Tumour adaptation to immune factors: old and new ideas for cancer immunotherapy

The tumour is fully functional in the zone of action of immune mediators. Moreover, the tumour needs immune system mediators to survive. "Adaptation" refers to a tumour's ability to withstand the effect of harmful elements. This gives birth to a new form of antitumour therapy: blocking tumour adaptability pathways. In this review, we will look at (i) tumour adaptation mechanisms as a result of pro-tumour immunoediting, (ii) how understanding tumour-adaptive mechanisms has led to ideas for developing cancer immunotherapies, and (iii) prospects for using the adaptation theory to substantiate new approaches to tumour growth inhibition. By considering the cancer problem through the lens of adaptability, a unique strategy for enhancing the efficacy of immunotherapy was proposed. The new approach is to utilise antisense treatment to erase the structural trace of adaptation in tumour cells or to disadapt tumour cells by "turning off" the immune system before initiating immunotherapy.

Transcriptomic Signature and Growth Factor Regulation of Castration-Tolerant Prostate Luminal Progenitor Cells

Background: The molecular and cellular mechanisms that drive castration-resistant prostate cancer (CRPC) remain poorly understood. LSCmed cells defines an FACS-enriched population of castration-tolerant luminal progenitor cells that has been proposed to promote tumorigenesis and CRPC in Pten-deficient mice. The goals of this study were to assess the relevance of LSCmed cells through the analysis of their molecular proximity with luminal progenitor-like cell clusters identified by single-cell (sc)RNA-seq analyses of mouse and human prostates, and to investigate their regulation by in silico-predicted growth factors present in the prostatic microenvironment. Methods: Several bioinformatic pipelines were used for pan-transcriptomic analyses. LSCmed cells isolated by cell sorting from healthy and malignant mouse prostates were characterized using RT-qPCR, immunofluorescence and organoid assays. Results: LSCmed cells match (i) mouse luminal progenitor cell clusters identified in scRNA-seq analyses for which we provide a common 15-gene signature including the previously identified LSCmed marker Krt4, and (ii) Club/Hillock cells of the human prostate. This transcriptional overlap was maintained in cancer contexts. EGFR/ERBB4, IGF-1R and MET pathways were identified as autocrine/paracrine regulators of progenitor, proliferation and differentiation properties of LSCmed cells. The functional redundancy of these signaling pathways allows them to bypass the effect of receptor-targeted pharmacological inhibitors. Conclusions: Based on transcriptomic profile and pharmacological resistance to monotherapies that failed in CRPC patients, this study supports LSCmed cells as a relevant model to investigate the role of castration-tolerant progenitor cells in human prostate cancer progression.

Choosing Kinase Inhibitors for Androgen Deprivation Therapy-Resistant Prostate Cancer

Androgen deprivation therapy (ADT) is a systemic therapy for advanced prostate cancer (PCa). Although most patients initially respond to ADT, almost all cancers eventually develop castration resistance. Castration-resistant PCa (CRPC) is associated with a very poor prognosis, and the treatment of which is a serious clinical challenge. Accumulating evidence suggests that abnormal expression and activation of various kinases are associated with the emergence and maintenance of CRPC. Many efforts have been made to develop small molecule inhibitors to target the key kinases in CRPC. These inhibitors are designed to suppress the kinase activity or interrupt kinase-mediated signal pathways that are associated with PCa androgen-independent (AI) growth and CRPC development. In this review, we briefly summarize the roles of the kinases that are abnormally expressed and/or activated in CRPC and the recent advances in the development of small molecule inhibitors that target kinases for the treatment of CRPC.

Cancer immunotherapy through the prism of adaptation: Will Achilles catch the tortoise?

There is no secret that despite the rapid development of new methods of cancer therapy, we still are not able to completely destroy the tumor. Every time we attack the tumor, the tumor neutralizes our attempts. Carcinogenesis can be presented as a tree whose branches are different pro-tumor mechanisms and whose trunk is a biological phenomenon that "feeds" those branches. A tree can be destroyed in two ways: either by cutting a branch for a branch without a guarantee that new branches will not grow, or cutting down the trunk and letting the branches wither away. To cut down the trunk, it is necessary to understand the nature of the biological phenomenon, which helps the tumor to avoid attack by the immune system, drugs and immunotherapy. The clue is that the pro-tumor mechanisms are united by one goal - to increase the resistance of the tumor cell to immune factors and drugs. A phenomenon that improves cell resistance is well known in biology - adaptation. If the immunity does not immediately destroy the tumor cell, the cell begins to adapt to it. Our hypothesis is that short range adaptation to immune factors plays a role in the formation of tumor tolerance for immunity and immunotherapy. This gives rise to the idea of reducing the survival of tumor cells by disrupting adaptation mechanisms. Indeed, "turning off" the immune system for a period of time before therapy and applying immunotherapy only to tumor cells that have lost their increased resistance could be a new approach to increase the effectiveness of immunotherapy.

Pharmacokinetic/Pharmacodynamic Modeling of Schedule-Dependent Interaction between Docetaxel and Cabozantinib in Human Prostate Cancer Xenograft Models

In this work, a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model to quantitatively describe the antitumor activity of docetaxel (Doc) and cabozantinib (Cab) under monotherapy, concurrent therapy, interval therapy, and different sequential therapy in mouse xenograft models of castration-resistant prostate cancer was developed and evaluated. The pharmacokinetics (PK) of Doc and Cab when administered separately and simultaneously were investigated in nude mice, and PD study was conducted in tumor-bearing mice treated with different dosing schedules. The PK interaction between Doc and Cab was expressed by adding the effect of Cab on the clearance of Doc in the PK model. And the PD interaction between the two drugs was demonstrated by the developed PK/PD model through the combination index "φ" Our results showed that the concurrent therapy and Doc followed by Cab (Doc ∼ Cab) sequential therapy exhibited better tumor inhibitory efficacy than monotherapy. The Cab followed by Doc (Cab ∼ Doc) sequential schedule was less effective than monotherapy, and the interval therapy did not enhance the antitumor efficacy compared with the concurrent therapy. The parameter φ estimated from the PK/PD model quantitatively characterized the action between Doc and Cab. There was no significant PD interaction between Doc and Cab in both the concurrent schedule and the interval schedule, whereas the effect of the two drugs in the "Doc ∼ Cab" and "Cab ∼ Doc" sequential schedule was synergistic and antagonistic, respectively. The proposed model properly described the antitumor effects of Doc and Cab under different treatment schedules and could be used for dose optimization through model-based simulation.

GABABR-Induced EGFR Transactivation Promotes Migration of Human Prostate Cancer Cells

G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) act in concert to regulate cell growth, proliferation, survival, and migration. Metabotropic GABA_B receptor (GABA_BR) is the GPCR for the main inhibitory neurotransmitter GABA in the central nervous system. Increased expression of GABA_BR has been detected in human cancer tissues and cancer cell lines, but the role of GABA_BR in these cells is controversial and the underlying mechanism remains poorly understood. Here, we investigated whether GABA_BR hijacks RTK signaling to modulate the fates of human prostate cancer cells. RTK array analysis revealed that the GABA_BR-specific agonist baclofen selectively induced the transactivation of EGFR in PC-3 cells. EGFR transactivation resulted in the activation of ERK1/2 by a mechanism that is dependent on G_i/o protein and that requires matrix metalloproteinase-mediated proligand shedding. Positive allosteric modulators (PAMs) of GABA_BR, such as CGP7930, rac-BHFF, and GS39783, can function as PAM agonists to induce EGFR transactivation and subsequent ERK1/2 activation. Moreover, both baclofen and CGP7930 promoted cell migration and invasion through EGFR signaling. In summary, our observations demonstrated that GABA_BR transactivated EGFR in a ligand-dependent mechanism to promote prostate cancer cell migration and invasion, thus providing new insights into developing a novel strategy for prostate cancer treatment by targeting neurotransmitter signaling.