CONTEXT: Under the supervision of Dr. Lily Wu, researchers at the University of California, Los Angeles created a prostate-specific two-step transcription amplification (TSTA) technique to deliver suicide gene therapy to hormone-refractory prostate cancer (HRPC), an aggressive cancer that is stubbornly resistant to conventional therapy.
RESULTS: In a study published in the May 15, 2005, issue of Clinical Cancer Research, lead author Dr. Makoto Sato tested a TSTA-driven adenovirus vector on three androgen-dependent and six HRPC cancers in mice. Optical imaging and PET/CT were used to monitor real-time gene expression. After three weeks of treatment with the adenoviral vector, optical imaging revealed vector activity in the androgen-dependent lines and four of the HRPC cell lines, all of which possess androgen receptors. These HRPC tumors displayed about seven times more luciferase expression than did androgen-dependent tumors. In addition, the HRPC tumors emitted PET signals that were more robust than those from the other tumors. While serum amounts of prostate-specific antigen leveled off in mice that received suicide gene therapy, PSA steadily increased in mice that received only saline. The researchers also treated a set of mice with a similar gene construct under the control of a constitutive viral cytomegalovirus (CMV) promoter. In contrast to mice treated with the TSTA construct, mice that received the CMV promoter revealed a high expression of thymidine kinase in the liver during PET/CT. Liver damage from the thymidine kinase was evidenced by elevated serum levels of liver transaminase.
IMAGE: PET/CT records results of suicide gene therapy. LAPC-4 tumors were injected with 109 infectious units of prostate-targeted AdTSTA-sr39tk or constitutive AdCMV-sr39tk vector. PET/CT imaging performed seven days later and prior to ganciclovir (GCV) treatment shows (top) tumor-limited expression in the TSTA-treated animal (left), but the CMV-treated animal shows strong expression in the liver as well. After GCV treatment (80 mg/kg per day from day eight to 15), fluorine-18-FHBG PET/CT signals at day 22 (bottom) are diminished in the tumors and the liver of the CMV animal. Histology performed at the day 22 endpoint (right) revealed extensive apoptosis, as shown in TUNEL-positive brown staining in the tumor and liver of the CMV-treated animal.
IMPLICATIONS:Data from the study support the conclusion that androgen receptor function is activated in HRPC despite low levels of androgen. Because most recurrent cancers express androgen receptors and PSA, the authors see the TSTA approach as a promising way to administer gene therapy to treat advanced prostate cancer.
Emerging AI Algorithm Shows Promise for Abbreviated Breast MRI in Multicenter Study
April 25th 2025An artificial intelligence algorithm for dynamic contrast-enhanced breast MRI offered a 93.9 percent AUC for breast cancer detection, and a 92.3 percent sensitivity in BI-RADS 3 cases, according to new research presented at the Society for Breast Imaging (SBI) conference.
The Reading Room Podcast: Current Perspectives on the Updated Appropriate Use Criteria for Brain PET
March 18th 2025In a new podcast, Satoshi Minoshima, M.D., Ph.D., and James Williams, Ph.D., share their insights on the recently updated appropriate use criteria for amyloid PET and tau PET in patients with mild cognitive impairment.
Can Abbreviated Breast MRI Have an Impact in Assessing Post-Neoadjuvant Chemotherapy Response?
April 24th 2025New research presented at the Society for Breast Imaging (SBI) conference suggests that abbreviated MRI is comparable to full MRI in assessing pathologic complete response to neoadjuvant chemotherapy for breast cancer.
Clarius Mobile Health Unveils Anterior Knee Feature for Handheld Ultrasound
April 23rd 2025The T-Mode Anterior Knee feature reportedly offers a combination of automated segmentation and real-time conversion of grayscale ultrasound images into color-coded visuals that bolster understanding for novice ultrasound users.