K-562 Cell Line Culture Protocol

Dillon Corvino

Culture and maintenance of the human K-562 erythroleukemia cell line, including thawing, routine passaging, and cryopreservation.

Protocol ID: HUM-K562-CULTURE
Version: v1.1
Author: Dillon Corvino

Purpose

This protocol describes the thawing, routine culture, maintenance, passaging, and cryopreservation of the human K-562 erythroleukemia cell line. K-562 cells grow in suspension and require regular monitoring of density to maintain viability and consistent growth rates.

Critical notes (read before starting)

• K-562 cells grow as suspension cultures and should remain in exponential growth phase.
• Do not allow cultures to exceed recommended density, as nutrient depletion reduces viability and alters phenotype.
• K-562 cells are of human origin—treat all cultures and waste as BSL2.
• Always pre-warm media and reagents to 37 °C before use.
• Ensure gentle handling; harsh centrifugation or over-pipetting can damage suspension cells.
• Cryopreservation requires 10% DMSO, and cells should be frozen using a controlled-rate freezing container.

Warning

Overgrowth (tight clumps, very dense cultures) leads to poor viability and altered functional responses. Split cultures before they exceed recommended density.

Tip

Record passage number and split ratios at every passage. This improves reproducibility when using K-562 cells as targets or stimulator cells.

Approximate timing

• Thawing: 15–20 min
  
• Routine medium change / split: 10–15 min
  
• Cryopreservation: 20–30 min
  
• Total hands-on time per session: ~15–30 min

Procedure

Step 1 – Reagents and medium preparation

1. Pre-warm complete culture medium:
   • RPMI 1640
     
   • 10% FCS
     
   • 1% Pen/Strep
     
2. Pre-warm PBS (if washing is needed).
   
3. Label flasks with:
   • Cell line name (K-562)
     
   • Passage number
     
   • Date
     
   • Operator initials

Step 2 – Thawing K-562 cells

1. Pre-warm 10–15 mL of complete medium to 37 °C.
2. Thaw a cryovial of K-562 cells in a 37 °C water bath:
   • Gently swirl and remove when only a small ice crystal remains.
3. Transfer contents into a 15 mL tube containing 10 mL pre-warmed complete medium.
4. Centrifuge at 300 g for 5 min at room temperature.
5. Remove supernatant and gently resuspend the pellet in 10–15 mL fresh complete medium.
6. Transfer cells to a T25 or T75 flask and incubate at 37 °C, 5% CO₂.

Note

The centrifugation step removes DMSO, preventing toxicity during recovery.

Step 3 – Routine culture and passaging

Recommended density

• Maintain between 2 × 10⁵ and 1 × 10⁶ cells/mL.

Procedure

1. Gently resuspend the culture by pipetting up and down.
2. Count cells using trypan blue or an automated counter.
3. If density > 1 × 10⁶ cells/mL:
   • Split culture 1:2 to 1:5 depending on growth.
4. Add fresh, pre-warmed complete medium to adjust culture to:
   • 2–3 × 10⁵ cells/mL
5. Return to incubator (37 °C, 5% CO₂).

Warning

Do not allow cultures to sit for more than 3–4 days without splitting. Nutrient depletion leads to apoptosis and growth arrest.

Step 4 – Short-term storage / holding conditions

• Cultures may be held at 2–4 × 10⁵ cells/mL for 24–48 h without splitting.
• If cultures appear slow or viability drops:
  • Increase medium volume
    
  • Spin down and resuspend in entirely fresh medium

Step 5 – Cryopreservation of K-562 cells

Preparation of freezing medium

• 90% FCS + 10% DMSO
  (or use BUF-FREEZE-MIX diluted 1:1 with cell suspension)

Freezing procedure

1. Collect cells in exponential growth phase.
2. Centrifuge at 300 g for 5 min.
3. Resuspend in freezing medium at 1–10 × 10⁶ cells/mL.
4. Aliquot 1 mL into labelled cryovials.
5. Place vials into a controlled-rate freezing container (e.g. Mr Frosty).
6. Freeze at −70/−80 °C overnight.
7. Transfer vials to liquid nitrogen for long-term storage.

Buffers Required

Full composition, preparation, storage, and safety information for each buffer lives in its own linked buffer document — only a concise per-buffer summary is reproduced here, generated automatically from that document.

2x Freezing Medium

Component	Final concentration / amount
RPMI 1640 (R0)	base medium (7 mL per 10 mL batch)
Fetal calf serum	10% (v/v)
DMSO (cell-grade)	20% (v/v)

• Final volume: 10 mL (2x concentrate; example batch, scale as needed)
• Preparation note: Mix gently by inversion; do not vortex. Keep on ice until use.
• Storage: Use fresh on day of preparation; do not store; discard any unused buffer.
• Caveat: DMSO is toxic at room temperature - keep the 2x mix on ice and mix with cells immediately after preparation. Final working freezing medium (after 1:1 mix with cells) contains 10% DMSO.

Full composition, preparation steps, storage, and safety information: BUF-FREEZE-MIX.

Materials

Reagents

Reagent	Supplier	Cat. #	Notes
RPMI 1640	Various	—	Base medium
Fetal calf serum (FCS)	Various	—	10% v/v in medium
Penicillin/Streptomycin	Various	—	1% v/v final
DMSO (cell culture grade)	Sigma/others	—	10% final in freezing medium
PBS, 1×	Various	—	For washing (optional)

Disposables

Item	Specification
T25 / T75 flasks	Vent-cap, sterile
15 mL / 50 mL tubes	Sterile
Cryovials	LN2-compatible
Pipette tips	Sterile (10 µL – 1000 µL)
Serological pipettes	Sterile (5–25 mL)

Equipment

Equipment	Specification / Notes
CO₂ incubator	37 °C, 5% CO₂
Benchtop centrifuge	300 g for washing
Biological safety cabinet	BSL2 handling
Water bath	37 °C for thawing
Cell counter/hemocytometer	For counting
Controlled-rate freezer	e.g. Mr Frosty
Liquid nitrogen storage	Long-term cryostorage

Troubleshooting

Issue	Possible cause	Solution
Low viability after thaw	Slow thawing or DMSO exposure	Thaw rapidly; wash immediately after thaw
Clumping	High density or depleted medium	Dilute, split earlier, or replace medium entirely
Slow growth	Old medium, poor serum batch	Prepare fresh medium; test new batch of FCS
Sudden drop in viability	Contamination or overgrowth	Check culture; discard and restart from stock

Safety (brief)

• Handle all human-derived cell lines using BSL2 precautions.
• Wear gloves, lab coat, and eye protection.
• Dispose of liquid and solid waste as biohazardous material.
• DMSO increases skin permeability—avoid contact.

Version history

Version	Date	Author	Changes
v1.0	2025-11-21	Dillon Corvino	Initial Quarto protocol for K-562 culture
v1.1	2026-09-18	Dillon Corvino	Replaced # Buffers used (bare library(tidyverse), leaked R package-startup warnings) with an auto-generated # Buffers Required section; moved it from after Materials to before Materials