Impact of Washing Processes on RNA Quantity and Quality in Patient-Derived Colorectal Cancer Tissues.

Background: Colorectal cancer (CRC) is a common and lethal cancer worldwide. Extraction of high-quality RNA from CRC samples plays a key role in scientific research and translational medicine. Specimen collection and washing methods that do not compromise RNA quality or quantity are needed to ensure high quality specimens for gene expression analysis and other RNA-based downstream applications. We investigated the effect of tissue specimen collection and different preparation processes on the quality and quantity of RNA extracted from surgical CRC tissues. Materials and Methods: After surgical resection, tissues were harvested and prepared with various washing processes in a room adjacent to the operating room. One hundred fourteen tissues from 36 CRC patients were separately washed in either cold phosphate-buffered saline reagent (n = 34) or Dulbecco's modified Eagle's medium (DMEM; n = 34) for 2-3 minutes until the stool was removed, and unwashed specimens served as controls (n = 34). Six tissue specimens were washed and immersed in DMEM for up to 1 hour at 4°C. Before RNA extraction, all specimens were kept in the stabilizing reagent for 3 months at -80°C. RNA was extracted, and the concentration per milligram of tissue was measured. RNA quality was assessed using the RNA integrity number (RIN) value. Results: Different washing processes did not result in significant differences in RNA quantity or RIN values. In the six tissues that were washed and immersed in DMEM for 1 hour, RIN values significantly decreased. The quality of the extracted RNA from most specimens was excellent with the average RIN greater than 7. Conclusions: RNA is stable in specimens washed in different processes for short periods, but RIN values may decrease with prolonged wash times.

Risks and cancer associations of metachronous and synchronous multiple primary cancers: a 25-year retrospective study.

BACKGROUND: The situation of patients developing multiple primary cancers is becoming more frequent and graver. This study investigated the risks of developing second primary cancers that are related to first primary cancers, and the interval times of synchronous and metachronous multiple primary cancers. PATIENTS AND METHODS: Retrospective data were retrieved from 109,054 patients aged ≥18 who were diagnosed with a first solid cancer and registered at Siriraj Cancer Center between 1991 and 2015. A two-month period between first- and second- primary cancers was used to differentiate metachronous and synchronous multiple primary cancers. The combinations of subsequent cancers and relative risks (RRs) of having multiple primary cancers versus having single primary cancer for the top-ten first and second primary cancers were examined. The RR was adjusted for age of the first primary cancer. A survival analysis of the time to second-primary-cancer development was performed. RESULTS: Multiple primary cancers were found in 1785 (1.63%) patients. Most (70.87%) second primary cancers occurred after 2 months of first breast, skin, colorectal, lung, head and neck, liver, male genital cancer-prostate, thyroid, and female genital cancer-non-uterine cancers, resulting in those cancers being classified as metachronous multiple primary cancer. After adjustment for age at first diagnosis, head and neck cancers had the highest metachronous association with second esophageal cancers (RR, 25.06; 95% CI, 13.41-50.77). Prostate cancer and second colorectal cancer also demonstrated a high metachronous association (RR, 2.00; 95% CI, 1.25-3.05). A strong synchronous association was found between uterine and ovarian cancers (RR, 27.77; 95% CI, 17.97-43.63). The median time from the first uterine cancer to second-cancer development was 55 days. CONCLUSIONS: The top-ten most frequent multiple primary cancers were the following: breast; liver; head and neck; colorectal; male genital cancer-prostate; skin; female genital cancer-uterine; thyroid; lung; and female genital cancer-non-uterine. Second primary cancers showed specific associations that depended on the first primary cancer. Physicians should be cognizant of the most common combinations and the interval times of metachronous and synchronous multiple primary cancers.