Prostate cancer biomarkers and its clinical relevance.

1. PROSTATE CANCER
BIOMARKERS
Sukhdev, CMC Vellore

2. Ideal tumour marker
 Should be non invasive
 Should diagnose a disease early
 Should comment on the prognosis accurately

3. Blood markers
Tissue markers Urine markers

4. BLOOD MARKERS

5.  PSA aka HK3
 PSA derivatives
 HK2
 HK4
 KLK 11,14,15
 ENDOGLIN
 PSMA

6. PROSTATE SPECIFIC ANTIGEN
 Misnomer
 Neither organ specific nor cancer specific
 Found in breast, breast milk, kidney and adrenals
 Found in other conditions like : renal and adrenal carcinoma and BPH

7. History of PSA
 PAP was used before prostate cancer
 But it was elevated only in prostate CA with bone mets

8. Rubin Flocks

9. Richard J Ablin
Coined the term Prostate specific antigen

10. Mitsuwo Hara
Initially isolated Gamma seminoprotein from semen for
identification in rape cases

11. T Ming Chu
 Was the first to relate PSA to
prostate cancer

12. Thomas Stamey
 PSA better than PAP
 PSA levels correlated with
volume of tumor

13. Metabolism of PSA
 Encoded by chromosome 19q13
 Glycoprotein(33 kDa) – 7% carbohydrates
 Coded in acinar cells
 DHT binds to androgen response elements and PSA gets translated as preproPSA
 preproPSA – 17AA = proPSA
 proPSA – 7AA = PSA
 PSA secreted into lumen of acinus
 1/4th inactivated and 3/4th stay activated
 The 3/4th active PSA is in bound form – antichymotrypsin and alpha2macroglobulin
 The 1/4th stay as free PSA
 The 3/4th is bound PSA

14.  Alpha2 macrogloblulin bound PSA is immunologically non reactive
 Antichyymotrypsin bound PSA is immunologically reactive

16.  A small fraction enters prostatic urethra and is excreted in urine
 Secreted PSA and not urinary PSA

17. Effects of CA prostate on PSA
 PSA is elevated not because of increased production but because of destabilisation
of architecture
 The luminal inactivating enzymes are lost and hence the free/total PSA ratio is less

18. Age specific PSA reference ranges
40-49 <2.5
50-59 <3.5
60-69 <4.5
70-79 <6.5

19. Clinical precautions before PSA
measurement
 DRE can sometimes elevate PSA, but this is insignificant
 Sexual activity elevates PSA, and so, PSA should not be done within 2 days of
sexual activity
 PSA should not be done within 6 weeks of prostate biopsy
 Finasteride users

20. Finasteride and PSA
 Finasteride lowers PSA when used for at least 6 months
 So, PSA has to be doubled if patient has been taking PSA for a year
 If ≥2 years, PSA * 2.3
 If ≥7 years, PSA * 2.5

21. PSA derivates
preproPSA(17AA leader sequence)
↓
proPSA(7 AA leader sequence) → Nicked PSA
↓
PSA
↓
Free PSA Bound PSA
BPSA

22. Free PSA
 PSA secreted into lumen of acinus gets deactivated by luminal enzymes
 In CAP, these enzymes are lost and so, fPSA is low
 f/t PSA is very useful in patients with PSA within grey zone.
 f/t PSA reduces unnecessary biopsies by 30%
2 situations in which f/t PSA is useful
 PSA between 4-10, if f/t PSA is >25%, no Bx necessary. And if <10%, Bx must. If 10-
25%, Bx for large prostates(>40 ml)
 Finasteride users : both free and total PSA decrease. So, instead of total PSA
adjustment, f/t PSA can be used

23. Nicked PSAs
 2 proPSA and 5 proPSA
2proPSA
 Nick between 5 and 7 AA
 %proPSA = compared to f/t PSA(30%), this reduced 60% of unnecessary prostate
biopsies

24. PSA kinetics
PSA velocity >0.8 ng/ml is significant for prostate CA
PSA density >0.1 is significant for prostate CA

25. PHI test • Prostate heath index
• Combines free/total PSA with 2proPSA isoforms
4K score test • Free PSA + total PSA + intact PSA + hK2

26. Circulating tumor cells
Rationale:
 If tumor cells are circulating, it means metastasis. So, can be used in diagnosis of metastatic disease
 Before there is clinical or radiologically apparent metastatic disease, CTCs are found, it can say, which
patient will progress to clinical mets
 If CTCs decrease in number, it can assess treatment response
2 current tests:
 CellSearch CTC – FDA approved
 CTC chip
CellSearch CTC
 Antibodies against – CD45,EpCAM,CK 8 and 18
 5 or more cells in 7.5 ml of blood – significant
 CD45 will be low in CAP
 Others will be high in CAP

27. Human
kallikrein 2
 This acts on proPSA to produce PSA
 PSA is more expressed in benign prostate tissue and less
expressed in cancerous tissue
 But, hk2 is less expressed in benign prostate tissue and more
expressed in cancerous tissue
 Also, hk2 is more expressed in higher gleason score tumors
and less expressed in lower gleason score tumors
 That is, hk2 is more expressed in poorly differentiated tumors
Hk4  Expressed in prostate,testis, adrenal
 Elevated in prostate cancer
KLK11  Low in prostate cancer
KLK14 and
15
 Patients post RP with elevated KLK14 and 15 will have
increased risk of progression

28. TISSUE BIOMARKERS

29. Glutathione S transferase • GSTP1
• Anti oxidant enzyme
• Hypermethylation of this region can lead to loss of
• This hypermerthylation is present in 100% of CAP and 80%
of PINs
[GSTM1 hypermethylation is seen in bladder cancer]
RAS association domain
family protein isoform A
• RASSFIA
• Hypermethylation present – aggressive tumor
TMPRSS-ERG fusion  Seen in tissue biopsies of 50% of CAP
 Seen in urine of 37% of CAP cases
Androgen receptor • Polymorphisms in AR can cause CRPC
• AR7 is the most significant one
HPC1(RNAase),
and MSR1
• Markers for screening in familial prostate cancer
microRNA • miR-141

30. ConfirmMDX test
Rationale:
Benign prostate tissue nearby malignant tissue shows distinct epigenetic alterations.
If,by sampling error, the malignant tissue is missed, epigenetic changes in the benign
tissue is indicative that malignant cells were present nearby which were missed by Bx
 Test is used to say whether the patient will need a rebiopsy after a negative biopsy
 This test is based on hypermethylation of 3 genes : GSTP1,APC,RASSF1[

31. URINE BIOMARKERS

32. Prostate Cancer Antigen3
 PCA3
 Measured in urine after prostate massage
 Detection using RT-PCR
OTHERS:
 Sarcosine
 AMACR – alpha methylacyl coenzymeA racemases

33. After a negative biopsy
 PHI
 4K score test
 ConfirmMDX test
 PCA3
Are useful to assess the need for rebiopsy