Role of novel imaging in the management of prostate cancer

Discovery of a novel 1H-pyrazole- [3,4-b] pyridine-based lysine demethylase 5B inhibitor with potential anti-prostate cancer activity that perturbs the phosphoinositide 3-kinase/AKT pathway

Lysine demethylase 5B (KDM5B) is a member of the Jumonji AT-rich interactive domain 1 family. Its main function is to demethylate di/trimethyl histone H3 lysine 4 and it plays a crucial role in the occurrence and development of cancer. In this study, we performed structure-based optimization of KDM5B inhibitors based on our previous work and the most active compound we synthesized was 11ad. Molecular modeling studies and thermal shift assays revealed that 11ad specifically targets KDM5B at the molecular and cellular levels. Crucially, 11ad demonstrated good pharmacokinetic properties and anti-prostate cancer activity in a xenograft model. Furthermore, unexpectedly, the specificity of 11ad for prostate cancer was found to be related to its inhibition of the phosphoinositide 3-kinase/AKT pathway. This is the first report of a KDM5B inhibitor affecting this pathway. Taken together, our findings indicate that 11ad is a novel KDM5B inhibitor that may serve as a lead compound for the development of treatments for prostate cancer.

Randomized Trial of Conventional Versus Conventional Plus Fluciclovine (18F) Positron Emission Tomography/Computed Tomography-Guided Postprostatectomy Radiation Therapy for Prostate Cancer: Volumetric and Patient-Reported Analyses of Toxic Effects

PURPOSE

Postprostatectomy radiation therapy planning with fluciclovine (¹⁸F) positron emission tomography (PET)/computed tomography has demonstrated improved disease-free survival over conventional only (computed tomography- or magnetic resonance imaging-based) treatment planning. We hypothesized that incorporating PET would result in larger clinical target volumes (CTVs) without increasing patient-reported toxic effects.

METHODS AND MATERIALS

From 2012 to 2019, 165 postprostatectomy patients with detectable prostate-specific antigen were randomized (arm 1 [no PET]: 82; arm 2 [PET]: 83). Prostate bed target volumes with (CTV1: 45.0-50.4 Gy/1.8 Gy) or without (CTV2/CTV: 64.8-70.2 Gy/1.8 Gy) pelvic nodes, as well as organ-at-risk doses, were compared pre- versus post-PET (arm 2) using the paired t test and between arms using the t test. Patient-reported outcomes used International Prostate Symptom Score and Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP). Univariate and multivariable analyses were performed and linear mixed models were fitted.

RESULTS

Median follow-up of the whole cohort was 3.52 years. All patients had baseline patient-reported outcomes, 1 patient in arm 1 and 3 patients in arm 2 withdrew, and 4 arm 2 patients had extrapelvic uptake on PET with radiotherapy aborted, leaving 81 (arm 1) and 76 patients (arm 2) for analysis of toxic effects. Mean CTV1 (427.6 vs 452.2 mL; P = .462, arm 1 vs arm 2) and CTV2/CTV (137.18 vs 134.2 mL; P = .669) were similar before PET incorporation. CTV1 (454.57 vs 461.33 mL; P = .003) and CTV2/CTV (134.14 vs 135.61 mL; P < .001) were modestly larger after PET incorporation. Although V40 Gy (P = .402 and P = .522 for rectum and bladder, respectively) and V65 Gy (P = .157 and P = .182 for rectum and bladder, respectively) were not significantly different pre- versus post-PET, penile bulb dose significantly increased post-PET (P < .001 for both V40 Gy and V65 Gy). On univariate and multivariable analyses, arm was not significant for any EPIC-CP subdomain. International Prostate Symptom Score and EPIC-CP linear mixed models were not significantly different between arms.

CONCLUSIONS

Despite larger CTVs after incorporation of fluciclovine (¹⁸F) PET, we found no significant difference in patient-reported toxic effects with long-term follow-up.

Novel indazole skeleton derivatives containing 1,2,3-triazole as potential anti-prostate cancer drugs

In this study, a novel batch of indazole containing 1,2,3-triazole agents were designed and synthesized. The antiproliferative activity of target compounds in four human cancer cells, PC-3 (human prostate cancer cell), MCF-7 (human breast cancer cell), HepG-2 (human hepatoma cell) and MGC-803 (human gastric cancer cell), was evaluated by thiazole blue (MTT). In the antiproliferative activity screening, we were surprised to find that most compounds have specific cytotoxicity to PC-3 cancer cells. In particular, 9a has an IC₅₀ value of 4.42 ± 0.06 μmol/L against PC-3 cell. Cloning experiments showed that 9a could inhibit the formation of PC-3 cancer cell clone in a dose-dependent manner. Through cell cycle arrest experiment, we found that compound 9a can block the cell cycle in G2/M phase and inhibit cell proliferation. Finally, by evaluating the safety of compound 9a, we noticed that it showed fairly good safety both in vivo and in vitro. Overall, based on the biological activity evaluation and safety, analogue 9a can be viewed as a potential lead compound for further development of novel anti-prostate cancer drug.

PET Use in Cancer Diagnosis, Treatment, and Prognosis

Tumorigenesis is a multistep process marked by variations in numerous metabolic pathways that affect cellular architectures and functions. Cancer cells reprogram their energy metabolism to enable several basic molecular functions, including membrane biosynthesis, receptor regulations, bioenergetics, and redox stress. In recent years, cancer diagnosis and treatment strategies have targeted these specific metabolic changes and the tumor's interactions with its microenvironment. Positron emission tomography (PET) captures all molecular alterations leading to abnormal function and cancer progression. As a result, the development of PET radiotracers increasingly focuses on irregular biological pathways or cells that overexpress receptors that have the potential to function as biomarkers for early diagnosis and treatment measurements as well as research. This chapter reviews both established and evolving PET radiotracers used to image tumor biology. We have also included a few advantages and disadvantages of the routinely used PET radiotracers in cancer imaging.

18F-fluciclovine PET/CT detection of biochemical recurrent prostate cancer in patients with PSA levels <2.00 ng/mL

OBJECTIVE

To establish the detection rate of prostate cancer recurrence following definitive therapy by 18F-fluciclovine PET/computed tomography (CT) in patients with biochemical recurrence (BCR) and prostate-specific antigen (PSA) levels less than 2.00 ng/mL.

METHODS

In this retrospective study, 78 patients with a PSA level of less than 2.00 ng/mL were selected from the 211 patients who underwent at least one 18F-fluciclovine PET/CT scan at our institution for the detection of biochemical recurrent prostate cancer between April 2017 and December 2018. Inherent differences in the characteristics of patients with and without a positive scan were investigated for possible associations using multivariable analysis.

RESULTS

One or more positive sites of recurrence were identified in 44 out of 78 patients (56.4%). Patients with a Gleason score between 8 and 10 were more likely to have a positive scan compared to patients with Gleason scores of 6-7 [adjusted odds ratio: 3.53, 95% confidence interval (1.13-10.99), P = 0.03]. No other significant association was found between PSA, T classification, and detection rate.

CONCLUSION

18F-fluciclovine PET/CT demonstrated a detection rate of 56.4% among patients with a PSA below 2.0 ng/mL. The results of this study support the use of 18F-fluciclovine PET/CT for the detection of recurrent prostate cancer at lower PSA levels, even at PSA levels less than 0.5 ng/mL.

Understanding and Improving 18F-Fluciclovine PET/CT Reports: A Guide for Physicians Treating Patients with Biochemical Recurrence of Prostate Cancer

The positron emission tomography (PET) tracer ¹⁸F-fluciclovine has seen increasing use to localize disease in men with biochemical recurrence of prostate cancer, i.e., elevated prostate-specific antigen (PSA) levels post-treatment. ¹⁸F-Fluciclovine PET/computed tomography (CT) imaging reports now play central roles in many physician-patient discussions. However, because no standardized grading system or templates yet exist for ¹⁸F-fluciclovine image assessment, reports vary in format, comprehensiveness, and terminology and may be challenging to fully understand. To better utilize these documents, referring physicians should be aware of six key features of ¹⁸F-fluciclovine PET/CT. First, ¹⁸F-fluciclovine is a radiolabeled synthetic amino acid targeting the amino acid transporters ASCT2 and LAT1, which are ubiquitous throughout the body, but overexpressed in prostate cancer. Second, ¹⁸F-fluciclovine image interpretation is predominantly visual/qualitative: radiotracer uptake in suspicious lesions is compared with uptake in bone marrow or blood pool. Location of ¹⁸F-fluciclovine-avid lesions relative to typical recurrence sites and findings elsewhere in the patient are considered when evaluating lesions' probability of malignancy, as is visibility on maximum intensity projection images when assessing bone lesions. Third, ¹⁸F-fluciclovine PET/CT detection rates increase as PSA levels rise. Fourth, detection rates may differ among centers, possibly due to equipment and reader experience. Fifth, since no diagnostic test is 100% accurate, scan data should not be used in isolation. Lastly, ¹⁸F-fluciclovine PET/CT findings frequently induce changes in disease management plans. In the prospective multicenter LOCATE and FALCON studies, scans altered management plans in 59% (126/213) and 64% (66/104) of patients, respectively; 78% (98/126) and 65% (43/66) of changes, respectively, involved modality switches. Referring physicians and imagers should collaborate to improve scan reports. Referrers should clearly convey critical information, including prescan PSA levels, and open clinical questions. Imagers should produce reports that read like consultations, avoid leaving open questions, and if needed, provide thoughts on next diagnostic steps.

Functional Expression of Choline Transporter-Like Protein 1 in LNCaP Prostate Cancer Cells: A Novel Molecular Target

Prostate cancer is one of the most common cancers in men. Choline PET or PET/CT has been used to visualize prostate cancer, and high levels of choline accumulation have been observed in tumors. However, the uptake system for choline and the functional expression of choline transporters in prostate cancer are not completely understood. In this study, the molecular and functional aspects of choline uptake were investigated in the LNCaP prostate cancer cell line along with the correlations between choline uptake and cell viability in drug-treated cells. Choline transporter-like protein 1 (CTL1) and CTL2 mRNA were highly expressed in LNCaP cells. CTL1 and CTL2 were located in the plasma membrane and mitochondria, respectively. [³H]Choline uptake was mediated by a single Na⁺-independent, intermediate-affinity transport system in the LNCaP cells. The anticancer drugs, flutamide and bicalutamide, inhibited cell viability and [³H]choline uptake in a concentration-dependent manner. The correlations between the effects of these drugs on cell viability and [³H]choline uptake were significant. Caspase-3/7 activity was significantly increased by both flutamide and bicalutamide. Furthermore, these drugs decreased CTL1 expression in the prostate cancer cell line. These results suggest that CTL1 is functionally expressed in prostate cancer cells and are also involved in abnormal proliferation. Identification of this CTL1-mediated choline transport system in prostate cancer cells provides a potential new therapeutic target for the treatment of this disease.

Anti-PSMA 124I-scFvD2B as a new immuno-PET tool for prostate cancer: preclinical proof of principle

Background

Prostate cancer (PCa) is the second leading cause of cancer-related death in the Western population. The use in oncology of positron emission tomography/computed tomography (PET/CT) with emerging radiopharmaceuticals promises accurate staging of primary disease, restaging of recurrent disease and detection of metastatic lesions. Prostate-specific membrane antigen (PSMA) expression, directly related to androgen-independence, metastasis and progression, renders this tumour associate antigen a good target for the development of new radiopharmaceuticals for PET. Aim of this study was to demonstrate in a preclinical in vivo model (PSMA-positive versus PSMA-negative tumours) the targeting specificity and sensitivity of the anti-PSMA single-chain variable fragment (scFv) labelled with ¹²⁴I.

Methods

The ¹²⁴I-labeling conditions of the antibody fragment scFvD2B were optimized and assessed for purity and immunoreactivity. The specificity of ¹²⁴I-scFvD2B was tested in mice bearing PSMA-positive and PSMA-negative tumours to assess both ex-vivo biodistribution and immune-PET.

Results

The uptake fraction of ¹²⁴I-scFvD2B was very high on PSMA positive cells (range 75–91%) and highly specific and immuno-PET at the optimal time point, defined between 15 h and 24 h, provides a specific localization of lesions bearing the target antigen of interest (PSMA positive vs PSMA negative tumors %ID/g: p = 0.0198 and p = 0.0176 respectively) yielding a median target/background ratio around 30–40.

Conclusions

Preclinical in vivo results of our immuno-PET reagent are highly promising. The target to background ratio is improved notably using PET compared to SPECT previously performed.

These data suggest that, upon clinical confirmation of sensitivity and specificity, our anti-PSMA ¹²⁴I-scFvD2B may be superior to other diagnostic modalities for PCa. The possibility to combine in patients our ¹²⁴I-scFvD2B in multi-modal systems, such as PET/CT, PET/MR and PET/SPECT/CT, will provide quantitative 3D tomographic images improving the knowledge of cancer biology and treatment.

Radiation therapy for prostate cancer: An evolving treatment modality

Radiation therapy for prostate cancer is evolving rapidly with advancing technology and with results from many clinical trials. This article summarizes highlights from the 5 articles published in this issue of Seminars on the current state of radiation treatment and areas of continued development.