DNA replication in yeast is initiated from discrete chromosomal locations (origins of DNA replication) controlled by sequential assembly of replication complexes that include the initiation proteins ORC, CDC6, CDC45 and MCM proteins. These initiation proteins are regulated in the cell cycles both in yeast and human. In human, hCDC6 and hMCM have been shown to be expressed in cycling but not in quiescent human cells. Antibodies against hCDC6 and hMCM proteins have been shown to be sensitive for cancer detection....[ Read more ]

DNA replication in yeast is initiated from discrete chromosomal locations (origins of DNA replication) controlled by sequential assembly of replication complexes that include the initiation proteins ORC, CDC6, CDC45 and MCM proteins. These initiation proteins are regulated in the cell cycles both in yeast and human. In human, hCDC6 and hMCM have been shown to be expressed in cycling but not in quiescent human cells. Antibodies against hCDC6 and hMCM proteins have been shown to be sensitive for cancer detection.

We have investigated whether detection of the mRNAs of the DNA replication initiation genes hCDC6, hMCM and hCDC45 in urinary cells from bladder cancer patients could be used as markers for cancer detection. We have analyzed urine samples from 44 bladder cancer and 3 bladder dysplasia patients, 23 bladder wash and 4 tissue samples from bladder cancer patients, 4 dysplasia tissue samples, 16 urine samples from ureteric stone or renal stone patients, and 30 normal urine samples as the negative controls. The molecular method RT-PCR was used to detect hCDC6, hMCM, hCDC45 and the internal control β-actin mRNAs. The results were compared to those obtained by clinical cystoscopy, biopsy and urine cytology. One hundred percent of the 47 urine samples from the 44 transitional cell carcinomas and 3 dysplasia cases gave positive signals for hMCM whereas 97% of the normal control samples gave a negative result. The expression of hCDC6 and hCDC45 was directly related to TCC grades. These results indicated that these DNA initiation genes can be used as detection markers for bladder cancer under the non-invasive condition, and may even for early detection of bladder cancer. Interestingly, most stone samples also gave positive signals. We have also analyzed 74 urine samples from patients underwent recurrence follow up for bladder cancer. The results showed that the molecular method with hCDC6 and hCDC45 could help to eliminate ~50% of the non-recurrence patients whom could be spared from the expensive and invasive cystoscopy. This could greatly reduce the cost and suffering of follow up surveillance of existing and future bladder cancer.

The RT-PCR method for cancer detection may not only detect bladder cancer but also cancer in other organs. We have tested this method for detection of nasopharyneal cancer (NPC) by detecting the ratio of hCDC6/β-actin as the marker. We have analyzed 18 NPC and 5 control samples. Fifteen out of the 18 NPC samples gave a ratio higher than 0.7 while 4 in 5 of the control had lower than 0.7 values. These findings suggest that the hCDC6/β-actin ratio in NPC tissues may be a useful diagnosis marker for NPC.